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Synthesis and some reactions of some diamino- and triaminophosphonium chlorides

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Title:
Synthesis and some reactions of some diamino- and triaminophosphonium chlorides
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Frazier, Stephen E
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Copyright Date:
1965
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English
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vii, 137 l. : illus. ; 28 cm.

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Subjects / Keywords:
Chlorides ( jstor )
Condensation ( jstor )
Infrared spectrum ( jstor )
Nitrogen ( jstor )
Phosphorus ( jstor )
Polymers ( jstor )
Quaternary ammonium compounds ( jstor )
Solvents ( jstor )
Sublimation ( jstor )
Trimers ( jstor )
Chemistry thesis Ph. D
Dissertations, Academic -- Chemistry -- UF
Nitrogen compounds ( lcsh )
Phosphorus compounds ( lcsh )
Polymers and polymerization ( lcsh )
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bibliography ( marcgt )
non-fiction ( marcgt )

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Thesis - University of Florida.
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Bibliography: l. 131-136.
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Vita.

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SYNTHESIS AND SOME REACTIONS OF SOME

DIAMINO- AND TRIAMINOPHOSPHONIUM

CHLORIDES



















By
STEPHEN EARL FRAZIER










A DISSERTATION PRESENTED TO THE GRADUATE COUNCIL OF
THE UNIVERSITY OF FLORIDA
IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE
DEGREE OF DOCTOR OF PHILOSOPHY











UNIVERSITY OF FLORIDA


December, 1965













ACKNOWLEDGMENTS


The author takes this opportunity to express his

sincere gratitude to his research director, Dr. Harry H.

Sisler. Although busy with administrative responsibilities,

Dr. Sisler has always provided enthusiastic encouragement

and offered valuable suggestions and advice concerning this

research. Dr. Sisler has also listened sympathetically to

the author's personal problems, and has been helpful in

obtaining the solutions to these problems.

The author wishes to recognize the interest given by

the other members of his committee and to thank them for

their assistance in preparing this dissertation.

A special note of appreciation should go to Dr. D. S.

Payne for the many valuable discussions and suggestions

shared during his visit at the University of Florida. The

author also wishes to acknowledge the help of his

colleagues, Dr. Donald F. Clemens and Mr. Robert L. McKenney.

A note of thanks goes to Mrs. Thyra Johnston who took a

personal interest in the typing of this dissertation.

Finally, the author wishes to thank W. R. Grace and

Company for the generous financial support of this work.













TABLE OF CONTENTS


Page


ACKNOWLEDGMENTS . . . . . .

LIST OF TABLES. . . . . . .

LIST OF FIGURES . . . . . .

CHAPTER

I. INTRODUCTION. . . . . .

II. HISTORICAL BACKGROUND . . .

Phosphonitrilic Derivatives.

The Chloramination Reaction.


* . .

* . .
. .


S 1

. 4


.. . . 4


III. REACTION OF THE CHLORAMINE-AMMONIA MIXTURE
WITH SUBSTITUTED DIPHOSPHINES AND
TETRAPHENYLCYCLOTETRAPHOSPHINE . . .

Experimental . . . . . . .

Discussion . . . . . . . .

Summary . . . . . . . .

IV. THE PYROLYTIC CONDENSATION OF
DIALKYLDIAMINOPHOSPHONIUM CHLORIDES AND OF
[(C2H5)2P(N2)-N=P(NH2)(C2H5)2C . .

Experimental . . . . . . .

Discussion . . . . . . .

Summary . . . . . . .. .

V. THE REACTION OF DIALKYLDIAMINOPHOSPHONIUM
CHLORIDES WITH TRI-, TETRA-, AND
PENTACHLOROPHOSPHORANES . . .

Experimental . . . . . .


iii







. . . .








CHAPTER Page

Discussion . . . . . . . 115

Summary. . . . .. . . . . 123

VI. GENERAL CONCLUSIONS AND SUMMARY . . . 125

BIBLIOGRAPHY. .... . . . . . . . 151

BIOGRAPHICAL SKETCH . . . . . . . .. 137











LIST OF TABLES

Table Page

1. Average P-N Bond Energy in (PNC12)n . . 8

2. Base Strength of Phosphonitrilic Derivatives
Toward Protons in Nitrobenzene and Water. . 14

3. Variation of P-N Stretching Frequency with
Electronegativity of Exocyclic Groups . . 15

4. Phosphonitrilic Derivatives Synthesized from
[PNC123,4. . . . . . . . . . 18

5. Infrared Absorption Data (Cm- ) . . . 34
6. Infrared Absorption Data (Cm-1) . .. . . 70

7. Effect of Ammonium Chloride on Product
Distribution. . . . . . . . . 76

8. N. M. R. Spectral Data for
[(C2H5)22P )-N(NH)-N=P(N2)(C2H5)2 C1 . . 81
9. Infrared Spectral Data, Cm-1. .- 97
9. Infrared Spectral Data, Cm .. 97










LIST OF FIGURES


Figure Page
1. Overlap of Npz Orbitals with Pdxz Orbital . 9

2. Pi-Electron Energy Levels of C6 6, (PNC12)3
and (PNC12)4 . . . . . . .. 10
3. Overlap of Pd -Orbitals with N -Orbitals . 11

4. Localized, Three-Center P-N-P Bonds in a
Phosphonitrile Segment. . . . . . 11
5. Minilab Reaction Flask. . . . . . 38
6. The Chloramine Generator. . . . . . 41
7. Infrared Spectrum of (C6H5)2P(O)NH2 (Nujol) 46
8. Infrared Spectrum of Intractable Chloramina-
tion Product of (C6H5)2P-P(C6H5)2 (Melt). .. 48
9. Infrared Spectrum of [(C6H5)2P(NH2)2]C
(Nujol) . . . . . . . . . 50
10. Infrared Spectrum of Intractable Chloramina-
tion Product of (C6H5P)4 (Thin Film). . . 53
11. Infrared Spectrum of [(C6H5P(NH2)3]C1 (Nujol) 55
12. Infrared Spectrum of C6H5P(O)(NH2)2 (Nujol) 56
13. Semimicro Sublimation Apparatus . . . 75
14. Infrared Spectrum of [(CH )2PN]n(KBr) . .. 77
15. H' N.M.R. Spectrum of
[(C2H5)2P(NH2)-N=P(N2)(C2H)2]Cl . . 80
16. Infrared Spectrum of [(n-C4H9)2PN]I (Melt). 85









Figure Page
17. Infrared Spectrum of CH3PC14 (Nujol) . . 102
18. Infrared Spectrum of (CH3)2PC13 (Nujol). . 103
19. Infrared Spectrum of (CH )2C14P3N3 (Nujol) . 105
20. Infrared Spectrum of [(C2H )2PN*C12PN]2 (KBr). 109
21. Infrared Spectrum of Suspected
[(CH )2PN.CH3C1PN]x (Thin Film). . . . 112


vii












CHAPTER I


INTRODUCTION


In recent years an area of study dealing with the

synthesis of phosphonitrilic derivatives and precursors

has been under investigation in our laboratories. Our

interest in this study was heightened by the discovery(1)

that diphenylchlorophosphine undergoes ammonolysis and

chloramination producing diphenylphosphonitrilic trimer

and a phosphonitrilic precursor,(2,'14

[(CH5)2P(NH2)-N=P(NH2)(C6H5)2]C1. On the basis of this
discovery a general reaction sequence was postulated in

which it was proposed that the chlorophosphine is

ammonolyzed with excess ammonia,

R2PC1 + 2 NH 3 R2PNH2 + NH4C1,

the aminophosphine reacts with chloramine to yield the

diaminophosphonium chloride,

R2PNH2 + NH2C1 [R2P(NH2)2]C1,

and the diaminophosphonium salt undergoes condensation

giving the observed products,







2

2[R2P(NH2)2]Cl [R2P(NH2)-N=P(NH2)R2]C1 + NH1Cl

[R2P(NH2)2]C1 + [R2P(NH2)-N=P(NH2)R2]C1 [R2PN]3

+ 2 NH4C .

Further evidence for this reaction sequence was

found in the study of the ammonolysis and chloramination

of dialkylchlorophosphines.) With dialkylchloro-

phosphines the chloramine-ammonia reaction produced di-

alkyldiaminophosphonium salts in which the alkyl group was

methyl, ethyl or n-butyl. In addition, the salt,

[(C2H )2P(NH2)-N=P(NH2)(C2H5)2]Cl, and the trimer,

[(n-C4H9)2PN](6) were produced. It was postulated that

these phosphonium salts should undergo self-condensation

reactions eliminating ammonium chloride and forming

phosphonitrilic derivatives. In addition, it was pre-

dicted that interesting phosphonitrilic derivatives should

result from the reactions of these salts with PCI RPC14,

or R2PC13 where R can be either an alkyl or an aryl group.

It was hoped that a study of these processes would not

only reveal a method by which cyclic derivatives could be

synthesized, but would also lead to high-molecular-weight

phosphonitrilic polymers.

Although it had been shown that diaminophosphonium

salts can be synthesized by chloramination and ammonolysis

of dialkylchlorophosphines, it was thought that these salts







5

might also result from the chloramination of substituted

diphosphines. An extension of this method to polyphosphines,
(RP)n, might also result in the synthesis of triaminophos-

phonium chlorides.

Therefore, the purpose of this study was (1) to

investigate the chloramination-ammonolysis of substituted

diphosphines and tetraphenylcyclotetraphosphine; (2) to

investigate the self-condensation reactions of diamino-

and triamino-phosphonium salts and

[(C2H5)2P(NH2)-N=P(NH2)(C2H5)2]C1; and (3) to investigate
the condensation reactions of some diaminophosphonium salts

with PC15, CH3PC14, and (CH )2PC13.












CHAPTER II


HISTORICAL BACKGROUND

Phosphonitrilic Derivatives


The first phosphonitrilic derivatives to be synthe-

sized were the phosphonitrilic chlorides, [C12PN]n, formed

by the reaction of PC15 and ammonia. This reaction was

noted by Liebig in 18354.7 Although Liebig did not

correctly deduce the empirical formula of the product of

this reaction, it was not long before other workers(8)

confirmed the formula [C12PN]n. The most significant early

study in this field was carried out by Stokes who published

a series of papers(9) dealing with the reaction of PC15

with NH4C1. He confirmed the formation of P3N3C16 and

P4N4C18, obtained the first reliable physical data on these

compounds, and studied their ammonolytic and hydrolytic

reactions. Stokes perfected the method of forming these

derivatives and discovered higher members of the homologous

series, [C12PN]n, from n=3 to n=7. It was Stokes who

originated the name "phosphonitrilic" polymer and who first

postulated, for the lower members, cyclic structures with

alternating phosphorus and nitrogen atoms. He also isolated

a highly polymeric phosphonitrilic "rubber," a discovery








5

which has contributed to the renewed interest in phospho-

nitrilic derivatives in recent years.
Since the discovery of the phosphonitrilic

chlorides, a large number of derivatives have been synthe-

sized in which the substituents on the phosphorus atoms

vary widely. These substituents can be halogens, pseudo-

halogens, alkyl-, perfluoroalkyl-, aryl-, aryloxy-, and

alkoxy-groups, N-substituted primary and secondary amines,

OH and several others.
The phosphonitrilic structure, first suggested by

Stokes, has been investigated and confirmed by infrared

and ultraviolet spectroscopy, nuclear magnetic and

quadrupole resonance studies, and electron and X-ray dif-

fraction. References to these works are listed in the
various reviews available on this subject.(10,11,12) The

phosphonitrilic derivatives are now known to contain a

backbone of alternate phosphorus and nitrogen atoms in

which all of the P-N bonds are of equal length. The

trimer, the first member of the homologous series, has a
planar, six-membered cyclic structure

Cl /Cl Cl C


N. > .
Cl I | Cl ClJ |,C1
ClS P Z 1 C?1 N 1Cl
N *N










The tetramer and higher members of the (R2PN)n series

(R=C1,F) through n=17 are also cyclic.(15) They are not

planar but have puckered configurations which give improved

overlap of d-orbitals on phosphorus with the lone-pair

orbitals on nitrogen providing increased delocalization of

the lone-pairs and hence, greater stability. In a number

of derivatives for which measurements have been made, the
O
average length of the P-N bond is 1.56 A. This bond length

depends on the group attached to phosphorus and on the size

of the ring since it is affected by delocalization of the

unshared pair on nitrogen. The N-P-N bond angles are all

about 1200, however, the P-N-P angle varies from 1200 to

1500 depending on the ring size and the substituents on

phosphorus. The P31 magnetic resonance spectra of the

cyclic derivatives in which the phosphorus atoms have the

same substituents have a single peak indicating that the

equivalence of the phosphorus atoms is independent of ring

conformation.

The bonding in phosphonitrilic derivatives is quite

interesting and a number of structural features can be

rationalized in terms of the bonding theories which have

been proposed. X-ray studies have shown that the phosphorus

atom is in an almost tetrahedral environment in the deriva-

tives studied. Thus its single bonds may be considered to

be formed using principally sp3 hybrid orbitals. In the










trimer the P-N-P angle is nearly 1200 and the nitrogen atom

is in a trigonal environment. The sigma-bonding electron

pairs and the lone-pair occupy approximate sp2 hybrid

orbitals. The fourth nitrogen electron pair occupies a 2-

orbital and can contribute to pi-bonding with phosphorus.

The pi-bonding in phosphonitrilics has excited a lively

controversy in the recent literature.(14,15) The struc-

tures shown above imply a resonance of the double bonds

and a bonding picture which is similar to that employed

for benzene. However, this analogy is complicated by the

necessity of using phosphorus d-orbitals in forming pi-

bonds. The d-orbitals are arranged in space in such a way

that considerable overlap with the nitrogen p-orbital, the

sp2-hybridized lone-pair orbital and with ligand orbitals

occurs. Several theoretical descriptions have been proposed

for this type of system.

Craig(16) has stated that because of the low local

symmetry of the phosphorus atom in phosphonitrilics, the d-

orbitals are completely non-degenerate. Four d-orbitals,

dy, dxz, dy, d 2 2, contribute to the overall pi-bonding
xy' xz yz x -y
(the d 2-orbital can be involved in exocyclic pi-bonding but

this is not considered to be of importance), and the contri-

butions need not be equal.

For pi-bonding, Craig considers the overlap of

phosphorus dxz-orbitals with nitrogen p -orbitals, shown in









Figure 1. The results of his molecular orbital calcula-

tions show that, unlike benzene, the highest energy bonding

orbital is non-degenerate, as shown in Figure 2. This

leads to an aromatic system of delocalized electrons which

is distinctly different from that encountered in carbon

compounds which utilize only p-orbital overlap. Any even

number of pi-electrons gives a closed shell. Huckel's

4n + 2 rule does not hold. This theory predicts that the

delocalization energy per electron increases steadily to a

limiting value as the number of pi electrons increases with

increasing ring size. Thus the trend in average P-N bond

energy (Table 1) is cited as a confirmation of this theory.

TABLE 1(16)

AVERAGE P-N BOND ENERGY IN (PNC12)n

n in (PNC12)n 4 6 2

E(P-N)n-E(P-N)3 (Kcal) 0 0.59 0.54 0.60 0.62

Dewar,(15) on the other hand, takes advantage of

the favorable symmetry properties of the dy orbital on

phosphorus as well as the favorable overlap properties of

the dxz orbital. Thus he has hybridized these orbitals

to form two new pi-orbitals: da (dxz + dyz) and

d b -(dxz dy
2

Figure 5 shows a N-P-N segment of the phosphonitrile

structure and illustrates the approximate geometry of the






















02


d
xz


Fig. 1.-Overlap of NZ Orbitals with Pxz
pz dxz


Orbital.























I


1 _I _1_


C6H6


(PNC12)3


IL

(PNC12)4


Fig. 2.-Pi-ElectrP E6gy Levels of C6H6, (PNC12)3 and
(PNC12)4. 6,2






\db


d /Ada


yz / 1
\ /






xz

/ \

/ \



Fig. 3.-Overlap of Pd -Orbitals with N -Orbitals.



new pi-orbitals. These hybridized pi-orbitals overlap
nitrogen pz orbitals on both sides of the phosphorus atom
to form the pi-bonding system. Instead of an extensive
aromatic system, however, this method describes P-N-P units
connected by localized three-center bonds (Fig. 4). The









Fig. 4.-Localized, Three-Center P-N-P Bonds in a
Phosphonitrile Segment.










relatively simple molecular orbital calculations indicate

that the delocalization energy is on the order of 0.82 no

where B is the resonance integral and n is the number of

P-N units. This is considered a high value and therefore

the theory predicts high stability for the phosphonitrilic

structure. Unlike Craig's theory, this approach indicates

that the properties which depend on the pi-system alone

should not change with increasing ring size. Certain

spectral measurements are cited in support of this

approach.(18)

Superimposed on the sigma- and pi-bonding in phospho-

nitriles is a third bonding system referred to as the pi'-

system. This system arises from the overlap of the d 2_y2

and d -orbitals of phosphorus with nitrogen lone-pair
xy
orbitals. As mentioned above, the unshared pair of elec-

trons on nitrogen occupies an s-p hybridized orbital. In

the trimeric molecules where the P-N-P bond angle is about

1200 this orbital is an sp2 hybrid. However, in the

tetramer and larger derivatives the bond angle becomes

greater, the lone-pair orbital obtains more p-character,

and greater overlap with phosphorus d-orbitals can occur.

Electron density can therefore increase on phosphorus at

the expense of nitrogen in this second delocalized system.

In rationalizing the chemical and physical properties

of phosphonitrile derivatives it is difficult to separate










the several effects arising from interactions of the three

bonding systems and the inductive effects of the substitu-

ents on phosphorus. An example of this is presented by

Feakins et al.,(19) in a thorough study of the basicity of

phosphonitrilic derivatives. The observed trend in base

strength as the ligands on phosphorus were changed, or as

trimers and tetramers were compared, could not be explained

by either pi-bonding theory alone. The data could be

rationalized, however, by considering the various effects

mentioned above, and the conclusion was reached that the

base strengths depend in a complex way on a number of

parameters.

It has been established that the base strength of(20)

phosphonitrilic derivatives is dependent upon the avail-

ability of nitrogen lone-pair electrons in the ring and

that protonation occurs on the ring. Thus, delocalization

of the nitrogen lone-pair into the region of the P-N bond

has the effect of decreasing the base strength and in-

creasing the P-N bond strength. Both of these effects are

sensitive to small changes in the ability of the substituent

on phosphorus to accept electrons and can therefore be

roughly correlated with the electronegativity of the sub-

stituent. Table 2 shows the increase in base strength of

certain derivatives with a decrease in the electronegativity

of the ligand.









TABLE 2(19)
BASE STRENGTH OF PHOSPHONITRILIC DERIVATIVES TOWARD
PROTONS IN NITROBENZENE AND WATER

R C1 OC2H5 C6H5 C2H5 NHC2H5 N(C2H5)2

pKa (NPR2)3 <-6.0 -0.2 1.5 6.4 8.2 8.5

pKa (NPR2)4 <-6.0 0.6 2.2 7.6 8.1 8.5

5.9 8.7
(water) (water)

6.5 8.7
(water) (water)

In the infrared spectra of phosphonitrilic deriva-

tives there occurs a strong band in the region of 1100-1400
-1
cm1 (see Table 3) which is attributed to P-N ring stretch-

ing. The position of this peak is quite variable and the

variation can be correlated with the electronegativity of

the group attached to phosphorus. If the group has a high

electronegativity the nitrogen lone-pair electrons can be

delocalized into the region of the P-N bond, strengthening

that bond and increasing the frequency at which the infra-

red peak occurs. Conversely, if the group has a low

electronegativity or is an electron releasing group such as

an amine, the nitrogen lone-pair is localized on the nitro-

gen atom and the P-N stretching frequency occurs at lower

energy. This effect is illustrated in Table 3.










TABLE 3

VARIATION OF P-N STRETCHING FREQUENCY WITH ELECTRONEGATIVITY
OF EXOCYCLIC GROUPS


Group Electro- (a) P-N Stretching Frequency, Ref.
negativity Cm-1

Trimer, Tetramer,
(R2PN)3 (R2PN)4

F 4.0 1305 1435 23

Cl 3.0 1218 1315 24

C6H5 1.74 1190 1213 25

CH3 1.57 1180 1220 26

NH2 1175 1240 27

C2H5 1.2 1157 1280 25

n-C4H9 0.9 1155 6

(a)Electronegativities of F and Cl are Pauling's(21)
values; others are calculated from the
formula,(22) X. = XH + 0.183 (D(R-H)-[D(R-R)-D(H-H)]} .

Obviously the foregoing discussion is a simplifica-

tion. Such properties as the base strength and P-N stretch-

ing frequency also depend on a number of factors not

mentioned in connection with the bonding theory. In any

thorough analysis one must consider the steric requirements

of the ligands, hydrogen-bonding of the ligands, and ring

conformation. These factors affect the overlap of ligand

orbitals and ring-nitrogen orbitals with phosphorus d-

orbitals and thus may change the expected order of base










strengths or the expected P-N stretching frequency. In

addition, the electron releasing or accepting abilities of

the groups on phosphorus will not affect the pi'-electrons

alone but will also affect the sigma- and pi-electrons to

some extent.

This brief discussion indicates the advancements

which have been made since Stokes' pioneering work in

understanding the structure and bonding in phosphonitrilic

derivatives. Clearly, more experimental data are necessary

for a complete evaluation of the bonding theories.

Since the work of Stokes, a wide variety of phospho-

nitrile derivatives have been synthesized. A large number

of derivatives may be synthesized because of the wide

variety possible in the nature of the groups attached to

the phosphorus atom. In addition, the groups on phosphorus

in a given molecule can be different from each other. In

the cyclic trimer, for example, the groups on neighboring

phosphorus atoms can differ. The methods of synthesis of

phosphonitrilic derivatives can be considered in two general

classes: synthesis from non-phosphonitrilic starting

materials, and substitution of the desired group on a previ-

ously synthesized P-N backbone. An example of the first

method is the synthesis of the phosphonitrilic bromides from

PBr5 and NH4Br. This method is analogous to Stokes' synthesis

of the phosphonitrilic chlorides and gives the trimer and










tetramer in about 50 per cent yield.(28,29) If one uses

mixtures of PC5 and NH4Br or

NH4C1 + PC15 [NPC12]3,4,n + HC1

NH4Br + PBr5 [NPBr2]3,4 + HBr

or
PBr + Br2 + NH4Br [NPBr2]3,4 + HBr

PBr5 and NH4C1 the products are mixed chlorobromides such

as P3N3C1 Br, P3N3C1Br2 and P3N3C12Br4'(30)

Most syntheses of new phosphonitrilic derivatives

have involved the substitution of different groups on

previously synthesized phosphonitrilic backbones. The

usual starting material for such a synthesis is the

phosphonitrilic chloride trimer or tetramer. Thus, the

fluorides can be synthesized by reaction of the chlorine

derivatives with fluorinating agents. A number of examples

of substitution reactions of this type are presented in

Table 4. This method is suitable for the synthesis of a

large number of phosphonitrilic derivatives(48) although

it has not been found to be generally useful for the

synthesis of alkyl or perfluoroalkyl phosphonitriles. Only

one example of the substitution of such a group is known

in the chemistry of cyclic phosphonitriles,

P3N C13[N(CH3)2]3 + CH MgBr P3N3(CH3)3 N(CH 3)23









18


c2,--












co
H OJ P
I I
p C\j t J rC\ 0 rC\ K 0 0 -





0











H
1L F H







i- 0z
S i- K1 -

0 II p


E4 o P 4 0 r0
.^ 1 oouO 0






SC\j C\j 0 0 0 M
H rm P
























c .1 r<1 . 11J K, 0N KN ,J
ri r-1 i M M
SE-i 0 Zr O O i-1 Z Z M Z












CO L. I I I i r C\ r\ L -i LJi L C\-
0a r-a K 0 -i -- P a a C r-a C
c 0 0 00 0Zp0

S r- 1m Fr- mO r








d -P Z Z Z rZ
oQ UU~U (t ^ o o + e i< o !z riw i
Wd- (D ^i cO CO (x h r c r o ^
^ W F U U U ii M ^ O O










19


0 Lt N

C- -
0- (N N j; ;
4-1










C-
LC r
li X

OOO L FN







c0 00
0 lA





Kn r\ tr\
p 01 P0
o o PA P PA

























,o m oj apq
o bo r^ i. k
.< C' LCN rC 01'~

rC H (\i C0' tN p Q Cn
0M ) P LCN O



CO O\ 4- i
k PA PA PA [1' IpH ji M'
PO L L4 LJ PA O PA PA




















4-,








c: A PA PA PA PA
wI~~ u uu uio










The above discussion refers only to cyclic phospho-

nitriles and their reactions. A renewal of interest in

macromolecular phosphonitriles has occurred in recent years

because of the possibility of finding products for military

and space industry use.

As mentioned earlier, Stokes discovered the first

highly polymeric phosphonitrilic "rubber" in 1897. Stokes

found that by pyrolyzing the cyclic phosphonitrilic

chlorides at about 3000 C a rubbery material was formed

which could be formulated as [PNC12]n where n is a large

number. This material is thermally stable up to about

3500 C where it begins to depolymerize yielding cyclic
derivatives. In certain cases(13,50) polymeric species of

the type, (PNC12)n*PC15, or H(PNC12)nC1, were formed di-

rectly from the reaction of PC15 with NH4C1. It has been

postulated(51) that the first product of this reaction is

ammonium hexachlorophosphate

NH4C1 + PC1 NH4PC16

This salt could undergo a series of condensation reactions

eliminating HC1

NH PC16 H2N-PC1 + 2 HC1 ,

H2N-PC14 HN=PC13 + HC1 .

The new species, HN=PC13, has two possible courses available

for further reaction. It can undergo intermolecular










condensation

nHN=PCl H=t=NPC12--nCl + n-1 H1 .
3 2 n

Or it can react with more PC15 to form the polymer,

SC Cl Cl
Cl \ /
P-E-N P---n1 .
Cl' n
Cl

Polymers in both these series are oils with n usually having

values of from 10 to 20.

Strong evidence(52) provided by conductance and

capacitance dielectricc constant) measurements and by

electron paramagnetic resonance studies, indicates that

the thermal polymerization of the cyclic phosphonitrilic

chlorides takes place by ionization of a chlorine atom

followed by an electrophilic attack by the positive

phosphonium ion


Cl C1 Cl Cl


:N N: :N N: + 01 ,
Cl I|,cl Cl ICl

Cl >N C1 Cl N
** **










Cl Cl

:Nl N: + C ,C'
ci I l ci I ici >
Cl P N N:
CC N
Cl


Cl Cl

N N

CI \C1 .1 C1 C1 [PNC12] 4
N N==P---N=P--N-"P- Cl- ,- >
Cl Cl (I



N N
cll 11 Cl

C1"N"' P C11- x CI


The other known halogen or pseudohalogen substituted
phosphonitriles undergo a similar polymerization at high
temperatures. The cyclic fluorides can be polymerized to
rubbery materials by heating to 3500 C5) The trimeric
and tetrameric bromides give an elastomer when heated to
250-3000 C. 28'29) Likewise, the cyclic isothiocyanates
polymerize when heated to 1500 C.(36,37) The average
molecular weight of the polymeric chloride formed by thermal
polymerization has been estimated to be as high as 300,000.










Although these halogen and pseudohalogen substituted

phosphonitrilic high polymers are thermally stable, they

all share the same disadvantage of being susceptible to

hydrolysis. Thus, upon exposure to moisture, HX is evolved

with the subsequent loss of theologically

interesting properties.

When the high polymers are heated considerably above

the temperature of formation, a depolymerization reaction

occurs and the cyclic derivatives are regenerated. One

observes, therefore, the operation of a dynamic equilibrium,

n(Unit) --m (Unit)n x m

cyclic linear

in which the products, or the average molecular weight of

the system will depend on concentration, pressure and

temperature. Depolymerization is favored thermodynamically

at higher temperatures since, in the expression,

AF = AH-TAS ,

the enthalpy is constant because the number of bonds in

many small molecules is approximately the same as the number

of bonds in a few large molecules made of the same amount of

material, and the entropy of many small molecules is greater

than the entropy of a few large molecules of the same amount

of material.(54)

Thermal polymerization has not been observed with

the cyclic phosphonitriles which have groups other than









halogens or pseudohalogens on the phosphorus atoms. How-

ever, linear polymers with alkyl groups, aryl groups or N-

substituted amines on phosphorus have recently been

synthesized by several new procedures. It has been shown,

for example, that lithium azide and sodium azide react

with halophosphines to produce intermediates which undergo

thermal polymerization giving high-molecular-weight phospho-
nitriles.(5556) The following reactions are illustrative

PBr3 + NaN -3 [Br2PN]n + N2 + NaBr

195-2000
elastomer

(C6H5)PC12 + NaN3 170-175 [C6H5ClPN]n + N2 + NaCl

average molecular weight >5000


(CF )2PC1 + LiN3 (CF)2 PN3 50-60 [(CF)2PN]n + N
33 2 3 mm Hg )2 2
M.P. 90-940 C
(57)
Diphenylphosphinyl azide undergoes a similar reaction.(5)
0
7
(C6H )2P(0)N3 + (C6H5)2PCl (C6H5)2P---N=P(C6H5)2-- Cl
n = 3,4

Furthermore, recently published results(58) indicate that
the pyrolysis of hydrazinophosphines produces polymeric
phosphonitrilic species










n C6H5PNHN(CH3)2 2 160-2200 [C6H5P[N(CH)2]N]n

+ n H2NN(CH )2

n P[NHN(CH )2]3 180)> [P[N(CH )2][NHN(CH )2]N]n

+ n H2NN(CH )2

Halophosphines have been shown to undergo reaction
with tetrasulfur tetranitride, S4N4, giving phosphonitrilic
(59,60,61)
polymers and precursors:(59,606)

PC1l + S N PNC l PCl -->PNC12

C6H5PC12 + N (C6H PNC1) 4C6H PC14

(C6H5)2PC1 + S4N4 [(C6Hs)2PN]x'(C6H5)2PC1

The only alkyl-substituted high polymer reported in
the literature to date was synthesized by methylating poly-
meric phosphonitrilic chloride(62) by slurrying the chloride
with a solution of methylmagnesium bromide or methyl-
lithium. A complete characterization of the products of
this reaction has not yet appeared in the literature.
With the recent increase in interest in phospho-
nitrilic chemistry has come the development of several new
methods of synthesizing these derivatives from non-
phosphonitrilic starting materials. Some of these methods
involve the ammonolysis of chlorophosphoranes and are quite
similar to the original preparation using ammonium chloride
or ammonia and PC15









C6 PCI + :Cl [(C6H5):CI 13 + HC

(C6 ) 2PC13 + ::H3(:H4C1) [(C6H 5)2P],4 + IH4cl(HC1)4)

(C:) : + :HE4Cl [(CH )2T x + EC1
..... (26)
[(C3) ]x ( 2-5)3 (CH)2 PN]3,4

(C2H)2^! + 5 -* [(C2H )2 :]x + :NHC1
E (C2 220-2-DO H (25)
2[(C 52]x 2> [(C2 5 2 3,42

The phosohonitrilic precursor,
[(C6H-)2 3(:2)-:- P(:T2)(C6H )2]Cl, has recently been shown
to undergo rinc closure reactions(3'4) with a number of re-
-.r.ts producing a variety of cyclic derivatives

l(CE ) : -: 2 6 H]C1 + PC1 (CH ) Cl PcN
[(C6-5)2P(- 5)-: ':= (:2)(CET5)2]Cl + PCI5 (CH5)4CI2P3N3

+ (C6Hs)aCl 4'4N

[(C )2 2 ( E2) )2]Cl + CH C14 -

(CGH5)5C!P3 3 + (C6s)6Cl12P4NT

[(C )7 ( 2) '-P( 2)(C )2]C1 + (C6 5 2PC3 -

C(C6Il) -] 3,4

3ao, Dresdner and Youn(65) have reported a unique
ethod for the s -thesis of [? ] In this procedure
Sor .S' F- is passed over PE5 at 7100 C, and the cyclic
derivatives distill from the reaction zone.









Perfluoromethyl- and perfluoropropyl-derivatives
have been synthesized by the chlorination of bis(perfluoro-
methyl)aminophosphine and bis(perfluoropropyl)aminophos-
phine.(66) This reaction is carried out at -300 C and it
is postulated that the intermediate, [R2P(NH2)C1]C1, is
first formed. Trimethylamine is added to the reaction
mixture at the completion of the chlorination

R2PNH2 + Cl2-->[R2P(NH2)C1]C1

[R2P(NH2)C1]C1 + (CH3 )N--[R2PN]3,4,n + (CH3 )N-HC1

This type of reaction is apparently quite general be-
cause it has been demonstrated by Sisler and coworkers(1'67)
that diphenylchlorophosphine produces phosphonitrilic
derivatives and precursors when reacted with gaseous mix-
tures of anhydrous chloramine and ammonia,(68) with H2NNH Cl
and H3NNH C12, and with solutions of anhydrous, ammonia-free
chloramine. As pointed out on page 2, the reactive inter-
mediate postulated in the reaction sequence leading to
phosphonitriles was the phosphonium ion, [(C6H5)2P(NH2)2] ,
when excess ammonia was used, or, [(C6H5)2P(NH2)Cl]I when
ammonia-free solutions of chloramine were used. These ions
could undergo intermolecular condensation producing the pre-
cursors which were isolated

2[(C6H5)2P(NH2)2]P->[(C6H5)2P(NH2)-N=P(NH2)(C6H5)2]

+ NH(,










2[(C6H5)2P(NH2)Cl]- [(C6H5) 2P(NH2)-N-P(Cl)(C6H5)2]
H
+ HC1
Indeed, the chloramination-ammonolysis of dialkylchloro-

phosphines(56) seems to follow a similar sequence and di-

alkyldiaminophosphonium chlorides were isolated from the

reaction mixtures.

The Chloramination Reaction

Chloramine, NH2C1, was first prepared and used as a

synthetic reagent by Raschig(69) in 1907. Raschig's method

consists of the addition of ammonia to dilute, aqueous

solutions of hypochlorite ion. Although this method has

the disadvantage that only dilute solutions of chloramine

can be obtained, and despite the difficulty in preparing

the completely anhydrous reagent, this process has been

widely used for many years for the commercial production

of hydrazine from chloramine and ammonia. In 1951, Mattair

and Sisler(70) found that anhydrous, gaseous chloramine

could be produced in excellent yields from the gas phase

reaction of ammonia and chlorine using an excess of NH3.

The first synthetic application of this method was the

production of anhydrous hydrazine

NH2Cl(g) + NH () NH2NH2() + NH4Cl(s)

Subsequently, chloramine was used to synthesize substituted









hydrazines from primary and secondary amines,(71) 1,1,1-
trisubstituted hydrazinium salts from tertiary amines,(72)
and aminophosphonium salts from tertiary phosphines.73)
These reactions may be generalized as follows
2 RNH2 + NH2Cl RNH-NH2 + [RNH 3C1 ,

2 R2NH + NH2C1 R2N-NH2 + [R2NH2]C1 ,

R3N: + NH2C1 [R3N-NH2]C ,

R3P: + NH2CI [R 3P-N H2]C .

Hart(74'75) examined thoroughly the chloramination
of aminophosphines and showed that chloramine attacks the
phosphorus atom instead of the nitrogen atom attached to
phosphorus, forming aminophosphonium salts instead of
hydrazinium salts
R2N-P(C6H5)2 + NH2C1 [R2N-P(C6H5)2NH2]1 ,

(R2N)2P(C6H5) + NH2C1 -C (R2N)2P(NH2)(C6H5)]CI ,

(R2N) P + NH2Cl [(R2N)3PNH2]C1 .

A similar study was undertaken by Clemens(76) using certain
aminophosphines and bis(phosphino)amines. The results were
analogous to those of Hart. With the bis(phosphino)amines
the reaction was postulated to follow the general course,










2
PR2 PR2
/ 2 / 2
RN + NH2Cl RN Cl
PR2 PR2


NH2 iNH
\ 2 2
PR PR2
RN Cl + NH3 RNT + NH4Cl
PR2 PR2


NH NH
1 II
PR^ PR
/ 2 / 2
RN + NH2Cl > RN Cl .
PR2 PR



The chloramination-ammonolysis of monochlorophos-

phines has been mentioned previously (pages 2, 28).

Since halophosphines can be synthesized by cleavage
(77,78)
of diphosphines and polyphosphines with halogens,(7,8)

it seems reasonable to expect chloramine to cleave the P-P

bond in a similar manner. However, alkylation of diphos-

phines with alkyl halides, which is formally analogous to

the chloramine reaction,() produces different results

with different diphosphines. For example, tetramethyl-,

tetraethyl-, and tetra-n-butyldiphosphine react with methyl

and ethyl iodide to form diphosphonium salts








R2P-PR2 + R'I [R2P-PR2R']I.77'80)

R = CH3, C2H5, n-C4H9

R' = CH3,C2H5

On the other hand, tetra-cyclohexyldiphosphine is cleaved
by methyl iodide as is tetraphenyldiphosphine
(C6H11)2P-P(C6H11)2 + CH3I -
(C6H11)2PCH3 + (C6H11)2PI
ICH3I ICH3I
[(C6H112P(CH )2]I [(C6H11)2P(CH3)I]I(77

(C6H5)2P-P(C6H5)2 + 3 CH3I [(C6H5)2P(CH3)2]I

+ [(C6H5)2P(CH3)I] .(81,82)

Burg(8) compares the R2P-group with a halogen or
pseudohalogen and states that diphosphines undergo many
reactions in a manner which is characteristic of halogens.
If one applies this idea to the chloramine reaction, one
would predict that phosphorus-phosphorus bonds would
undergo cleavage with chloramine.













CHAPTER III


REACTION OF THE CHLORAMINE-AMMONIA MIXTURE WITH SUBSTITUTED
DIPHOSPHINES AND TETRAPHENYLCYCLOTETRAPHOSPHINE


Experimental


Manipulation of materials.-The diphosphines used in

this study are extremely sensitive to oxygen, and detailed

precautions were taken to prevent contamination by oxygen

from the air. Similarly, some of the products formed in

this study are sensitive to moisture, and precautions were

taken to avoid contamination of solvents and other reagents

by moisture.

Benzene was either obtained as the reagent grade

product and stored over calcium hydride or obtained as the

technical grade product and distilled and stored over

calcium hydride. Petroleum ether and diethyl ether were

obtained as reagent grade products and were stored over

calcium hydride. Other solvents used were reagent grade.

Tri-n-butylphosphine was obtained from Food Machinery

and Chemical Corporation and used as obtained. Phenyl-

dichlorophosphine and diphenylchlorophosphine were obtained

from Victor Chemical Works and used as obtained. These

reagents were transferred by pipette under a stream of dry










nitrogen. Tetramethyldiphosphine and tetraethyldiphosphine

are liquids at room temperature and were purified by distil-

lation at reduced pressure. They were stored and transferred

by pipette under nitrogen in a D. L. Herring Model HE-43

Dri Lab equipped with a Model HE-93 Dri Train. Tetraphenyl-

diphosphine and tetraphenylcyclotetraphosphine are solids

and were stored and transferred under nitrogen in the dry

box.

Infrared spectra.-Infrared spectra of the compounds

produced in this study were determined using a Perkin-Elmer

Model 337 grating infrared spectrometer. A summary of the

spectral bands of these compounds between 2.5 and 25

microns is presented in Table 5.

Solid samples were examined between KBr disks as

Nujol mulls, or, when the solid melted below 100C, as a

melt. In certain instances thin films could be obtained by

carefully evaporating a chloroform solution of the sample

on a KBr disk. Samples of substances which are sensitive

to moist air were prepared for infrared analysis in the dry

box.

Elemental analyses.-Elemental analyses and molecular

weight determinations were performed by Galbraith Labora-

tories, Inc., Knoxville, Tennessee. Several nitrogen

analyses were carried out in these laboratories using a

Coleman Model 29 Nitrogen Analyzer.






34
TABLE 5(a)
INFRARED ABSORPTION DATA (Cm-1)
[(CH3)2P(NH2)2]C1, Nujol Mul1(6)
3920(w), 3850(w), 3260(vs,b), 2940(vs), 2850(vs),
2620(m), 2560(w,sh), 2530(w,sh), 2400(m), 2260(vw),
2200(w), 2160(w,b), 2100(w,sh), 2060(w), 2000(w),
1940(m), 1625(w), 1570(s), 1460(s) 1420(s), 1410(m,sh),
1375(m), 1310(m), 1300(s), 1070(sh5, 1040(s), 990(s),
951(s), 885(m), 860(m), 835(m), 762(s), 695(s),
600(b), 527(b).
[(C2H5)2P(NH2)2]C1, Nujol Hull(6)
3940(w), 3160(vs), 3060(vs), 2940(vs,b), 2850(vs),
2640(w), 2550(w), 2330(w,sh), 2150(w), 2060(w),
1960(w,sh), 1920(w), 1870(w,sh), 1755(w,b), 1665(w,b),
1560(s), 1460(vs), 1395(s), 1380(s), 1275(s),
1240(m), 1160(w,b), 1075(s,sh), 1050(s), 1019(s),
980(s,sh), 968(s), 910(s), 761(s), 733(s), 721(s),
665(s), 625(s,b), 500(w,b), 447(m).
(C6H5)2P(0)NH2, Nujol Mull
3240(s,b), 3125(s), 2940(vs), 2860(vs), 1970(w),
1900(w), 1820(w), 1779(w), 1680(w), 1595(m),
1560(s), 1485(m), 1460(vs,b), 1440(vs,sh), 1439(vs),
1420(w,sh), 1380(s), 1365(m,sh), 1340(w), 1310(m),
1275(w), 1260(w), 1175(s), 1110(s), 1105(s),
1060(m), 1010(w), 990(m), 910(s), 858(w), 849(w),
752(s), 720(s), 695(s), 620(w), 532(s), 518(s),
488(m), 439(w).
[(C6H5)2P(NH2)2]C1, Nujol Mull
3170(s), 3075(s), 2980(vs,sh), 2940(vs), 2860(vs),
2710(w), 2540(w b), 2440(w), 1970(w), 1900(w),
1815(w), 1780(w), 1665(w,b), 1595(m), 1560(s),
1485(m), 1460(s), 1440(s), 1410(m), 1380(s),
1365(m,sh), 1340(w), 1320(w), 1280(w), 1190(w),
1160(w), 1110(s), 1075(w,sh), 1025(s,sh) 1010(s),
990(s,sh), 980(s), 922(m), 910(m), 855(w), 840(w),
756(s,sh), 751(s), 742(s), 720(s), 691(s), 638(w,b),
620(w), 549(w,b), 510(s), 505(s,sh), 472(m), 434(w),
413(m).








Table 5 (cont'd)
CH NHH1H CH THo
6 / 2 C6 / 2
Suspected C- [ ---NP=N ---P NH, Melt

3400(s,sh), 3210(vs), 3060(vs), 2950(s), 2940(sh),
2635(w), 2600(w), 2300(m), 2250(w), 1960(m),
1900(m), 1820(m), 1770(w), 1720(w), 1670(m),
1640(m), 1590(s), 1550(vs), 1480(s), 1440(vs),
1280(s,sh), 1205(vs,vb), 1115(s), 1015(m), 910(m,b),
799(m), 742(s), 692(s), 685(sh), 615(w), 502(s,vb).
[(C6E5)P(NH 2)]Cl, Nujol Mull
3375(m) 3250(s,sh), 3170(s), 3075(s), 2940(s,sh),
2900(vs), 2850(s), 1590(w), 1559(m), 1460(s),
1440(s), 1415(m), 1380(s), 1135(s), 1084(w),
1070(w), 1025(w), 985(m), 925(-,sh), 875(m),
798(w), 763(s), 721(w), 705(w), 692(m), 620(w,b),
510(m), 474(m).
(C6H5P(0)(NH2)2, Nujol Mull
3350(s), 3275(s,sh), 5220(s), 3110(s,sh), 3055(m),
2940(vs), 2850(vs), 2740(w), 1955(w), 1900(w),
1770(w), 1590(m), 1560(m), 1460(s), 1440(s), 1410(m,b),
1580(s), 1330(w), 1310(w), 1182(m), 1155(vs),
1118(s), 1060(m), 1010(m), 959(s), 915(m,sh),
885(m), 855(w), 745(s,sh), 740(s), 720(m), 694(s),
620(w), 568(w,b), 520(s), 512(s), 494(w), 435(w,b).

(a)s,strong; m,medium; w,weak; b,broad; v,very;
sh,shoulder.








36

oelting points were determined in a Thomas-Hoover

capillary mel` ": point a ratus and are uncorrected.

e Iaraion of sstituted diDhosohines and tetra-

. .he c. o tr .
tetraethydi oni wne were prepared by the desulfuration of

the corresoo_. 1- dipho ."'i disulfide with tri-n-butyl-

phosohine. The dipho -:..e disulf1ies were synthesized

by the Gri -.. -d method from PC1 and <_,-3r(R = CH C2H ).
(5,85,s6)
This ethod has ben zhoroi. :ly discussed elsewhere. '

To the solid Adihosphine disulfide under a nitrogen atmos-

phere as x ed by pipette, tri-n-butylphosphine according

to the stoichio etry of the following general equation

)- )p + 2(C9) 3 R P-PR2 + 2(CH9)3P(S)

It was convenennt in his study to use from ten to fifteen

S- of the diphosphine sulfide in each run and to mix the

re ts in a 1l round-botto:ed distillation flask. The

mixture was then heated under reduced pressure. The tetra-

1 idi:ho>hine was o gained by fractional distillation

fro: he reaction mixture. The observed boilir.- point of

tet.a,.t, diphos3hine was 350 C at 16 mm ,-(Lit. :)

3o- = -0 C). -:e observed bill" ooint of tetra-

Shyldciphsphine was 67 C at 1.7 mm : -(Lit. : Bp74
S-o ). Yields of tetraaikyldiphosphine from this re-

action :ed between 3 and 80 per cent of theory based on

te amount of diphosphine disulfide used. Distillation was










slow because of the difficulty in removing the diphosphines

from (C4H9)3PS in which they are soluble.(84) At the

completion of the distillation the diphosphines were placed

in stoppered receivers under nitrogen and stored in the dry

box until needed. The infrared spectra and nuclear magnetic

resonance spectra of these tetraalkyldiphosphines have been

treated thoroughly elsewhere(84) and need not be considered

here.

Tetraphenyldiphosphine was prepared by the reaction

of tri-n-butylphosphine with diphenylchlorophosphine(87)

which can be represented by the following equation

(C4H9)jP + 2(C6H5)2PCl (C6H5)2P P(C6H5)2

+ (C4H9)3PC12

In a typical experiment, 3.15 ml (14 mmoles) of tributyl-

phosphine was pipetted into 5.0 ml (27 mmoles) of diphenyl-

chlorophosphine in a Minilab reaction flask (Fig. 5) fitted

with a stirrer and a nitrogen inlet and outlet. The

mixture was stirred until it became homogenous. It was then

allowed to stand under a nitrogen atmosphere for about three

days. At the end of this time the reaction mixture had

become a solid, crystalline mass. This crystalline mixture

was extracted under a nitrogen flow with cool, freshly

boiled, distilled water until the washings gave no chloride

tes7 with aqueous silver nitrate. The white, crystalline
















Nitrogen
Inlet










Stirrer









Stirrer


Fig. 5.-Minilab Reaction Flask.


Filter










residue was dried in vacuum and transferred to the dry box.

. P. 118-121 C (Lit.(78): M. P. 120.5 C). The average

yield of tetraphenyldiphosphine produced by this method of

synthesis was about 40 per cent of theory based on the

amount of diphenylchlorophosphine used. Although strict

precautions against oxidation of the diphosphine were

taken, a small amount of tetraphenyldiphosphine monoxide(88)

was probably present in each sample.

Tetraphenylcyclotetraphosphine was prepared by the

reaction of tri-n-butylphosphine with phenyldichloro-

phosphine 87) as indicated by the following equation

4(C4H9)3P + 4 C6H5PC12 (C6H5P)4 + 4(C4H9)3PC1

In a typical experiment, 5.0 ml (36.6 mmoles) of phenyl-

dichlorophosphine was pipetted into 8.24 ml of tri-n-butyl-

phosphine in a Minilab reaction flask (Fig. 5) under

nitrogen. Heat was evolved and after a few moments of

stirring the reaction mixture became a solid, crystalline

mass. When the mixture had cooled to room temperature, it

was extracted with copious amounts of absolute ethanol.

This extraction was continued until the acidified washings

gave no precipitate with aqueous silver nitrate. The white,

crystalline residue was dried in vacuum and transferred to

the dry box. M. P. 153-1550 C (Lit.(89): M. P. 155-1550 C).

The average yield of tetraphenylcyclotetraphosphine produced











- t his ethod of synthesis as 50 per cent of theory based

on amoun of ohenyldihlorophosphine used. Strict pre-

cautins .were ta en to avoid oxidation of the product.

7-e o an-d
e nrae s ra of tezraphenyldiphosphine and

tc-a~pn lc cloterao osine are available in the

_I~ ... . :;oer, a controversy exists in the cur-

ret te oce ni she nature of tetrapheny1cyclo-

to Cno' e e material produced in this study

s n:rj ana infrared spectrum reported for

"form A" ch is considered to be one stereoisomeric form

o. ( 7

? r- "".r... e-on 0o .lorai :e. -e preparation of

seous chlor -ine was carried out in a generator shown

cia a...: tical in y iure 6.( n In'. 'eous an onia,

clorine and nitro n --ere eeterea in rotareters and mixed

in s reaction tube. The roximate rate of intro-

duction hf ses was: 12, .1 mole/hr.; : 1.2

olh. oie, .. he approximate production rate

of c lora e as 0..1 mole/hr. Since anmonia was present

S 1, exc-ess of at -t -uired by the stoichiometry of


-I ecrc- 12L


+ 1 ( (s) 2'

consisted of c'bor -ine, anmonia and

r:;s ol iL were -laced in the reaction tube













Qa~~d
Soz
S-P
0 *2 <
1O,










to filter out the finely divided ammonium chloride produced

in the reaction. The effluent gases were bubbled into a

receiver containing the solution of the substance to be

chloraminated.


The Reaction of the Chloramine-Ammonia Mixture
with Tetramethyldiphosphine

(CH3)2P-P(CH3)2 + 3 NH2C1 + 2 NH 2[(CH3)2P(NH2)2]C1

+ NH4C1

In a typical experiment, 1.0 ml (7.1 mmoles) of

tetramethyldiphosphine was dissolved in 75 ml of dry benzene

and exposed to the effluent gases of the chloramine genera-

tor. A reaction took place immediately. A white precipitate

formed and the reaction mixture grew warm. After 10-15

minutes of chloramination the reaction appeared to be

complete and the temperature of the mixture dropped to about

200 C because of evaporation of the solvent. Chloramination

was continued for 5-10 minutes beyond this point to insure

exposure of the reaction mixture to an excess of chloramine.

At the completion of the chloramination the benzene was re-

moved by filtration. The solids remaining on the filter

were extracted with 60 ml of hot, 50/50 ethanol-acetone

mixture. White crystals precipitated from the solution as

it slowly cooled to room temperature. These crystals were

removed by filtration and dried in vacuum. M.P. 191-1940 C.










Anal. Found: N, 21.47. Calculated for [(CH3)2P(NH2)2]C1:

N, 21.79. The infrared spectrum of this material was
identical with that of dimethyldiaminophosphonium chloride

(M.P. 192-1940 C) produced by chloramination-ammonolysis

of dimethylchlorophosphine.(5'6)

Addition of petroleum ether to the mother liquor

caused a larger portion of dimethyldiaminophosphonium

chloride to precipitate. Yield: 1.08 g (63% of theory).

The Reaction of the Chloramine-Ammonia Mixture
with Tetraethyldiphosphine

(C2H5)2P-P(C2H5)2 + 5 NH2C1 + 2 NH3 2[(C2H5)2P(NH2)2]C1
+ NH4C1

3(C2H5)2P-P(C2H5)2 + 9 NH2C1 + 6 NH3 2[(C2H5)2PN3
+ 9 NH4C1

Tetraethyldiphosphine (5 mmoles) was dissolved in

75 ml of dry benzene and exposed to the effluent gases of
the chloramine generator. A white precipitate formed

immediately and the solution became warm. After 10-15

minutes the temperature of the solution fell to about 200 C

because of evaporation of the solvent, and the reaction

appeared to be complete. Chloramination was continued,
however, for 5-10 minutes longer until a relatively large

excess of chloramine and ammonia had been added to the re-

action mixture. The benzene solution was removed from the










precipitate by filtration and evaporated to dryness. A trace

of oily crystals was observed. The crystalline material was

separated from the oil by dissolving it in 30-600 petroleum

ether. The oil was discarded. Evaporation of the petroleum

ether yielded crystals which melted at 113-1150 C and which

sublimed readily at 30-400 C and 0.1 mm Hg. This material

was identified by its infrared spectrum and melting point

(see Chapter IV for a more complete description of the

identification of this material) as diethylphosphonitrilic

trimer(25) (Lit: M.P. 117-1190 C). Yield: trace (1-5

millig.).

The solids remaining on the filter were extracted

with three, 10 ml portions of absolute ethanol. This solu-

tion was evaporated to dryness and the resulting crystalline

extract was dissolved in 10-15 ml of hot, 50/50 ethanol-

acetone mixture. This solution was cooled with an ice bath

and to it was added approximately 100 ml of 60-1100

petroleum ether. The product crystallized from the solution

as well formed, white needles. These crystals were filtered

and dried in vacuum. M. P. 103-1050 C. Anal. Found: N,

17.9. Calculated for [(C2H5)2P(NH2)2]C1: N, 17.89. The

infrared spectrum of this material was identical with that

of diethyldiaminophosphonium chloride (M. P. 106-108.50 C)

produced by the chloramination-ammonolysis of diethylchloro-

phosphine.(5'6) Yield: 1.07 b (68% of theory).










The Reaction of the Chloramine-Ammonia Mixture
with Tetraphenyldiohosohine

In a typical experiment, 1.05 g (2.8 mmoles) of

tetraphenyldiphosphine was dissolved in 50-75 ml of dry

benzene and exposed to the effluent gases of the chloramine

generator. A white precipitate formed immediately and the

reaction mixture grew warm. Chloramination was continued

for about 20 minutes to insure exposure of the reactants

to an excess of chloramine. At the completion of the re-

action the temperature of the reaction mixture had fallen

to about 20 C because of evaporation of the solvent. The

benze-l, solution was removed from the white precipitate by

filtration and the solids were washed with 25 ml of fresh

benzene. The combined filtrate and washings were evapo-

rated to dryness yielding 0.39 g of a white powder which

melted in the range of 80-1100 C. This solid was redis-

solved in 10 ml of boiling benzene. Upon cooling, white

crystals precipitated from the benzene solution and were

filtered and dried in vacuum. M. P. 158-1600 C. Anal.

Found: N, 6.6. Calculated for (C6H5)2P(0)NH2: N, 6.48.

The infrared spectrum (Fig. 7) is consistent for the formu-

lation, (C6H5)2P(0)N2.(91) Evaporation of the benzene

solution to dryness yielded an oily foam. More crystalline

(C6H5)2P(0)NH 2 could be recovered from this foam by dis-

solving it in 2-4 ml of boiling benzene, adding hexane to

















--1.















I O




v

i TS~ c\




C:

r-i

ri
if
re I ;"
ri r: ~C
uU



F-e L-i
i n
i?
i a

F?
;.rr
e: o

Cj i;i
Z: :1





~--i

L^
6"
i---0


4\
..1
ri
?
ri







i"



Pii








rr\










the hot solution until it became cloudy, and allowing this

mixture to stand for several hours. By repeating this

process several times, all but a trace of the sample was

recrystallized and shown by its melting point and infrared

spectrum to be (C6H )2P(0)NH2. The noncrystalline residue

was a yellow oil and was discarded.

In other experiments, evaporation of the benzene

solution yielded a dark foam which appeared to be air

sensitive, turning wet upon exposure. After recovery of

the first crop of crystalline (C6H5)2P(0)NH2 from this

mixture, further attempts at recrystallization resulted in

the formation of oily products. The dark foam produced by

evaporation of the benzene solution melted at 35-400 C.

Its infrared spectrum is shown in Figure 8.. Anal. Found:

C, 65.54; H, 6.03; P, 12.67; N, 6.06; Mol. Wt. (cryoscopic

in benzene), 450. The P:N ratio is 1:1. This implies the
C6H C,6H5
structural unit, -E-P=N-}- for which the calculated

composition is: C, 72.4; H, 5.1; P, 15.6; N, 7.0. The

analysis, however, is low and indicates that the material

may consist also of oxygen-containing material.

The benzene-insoluble solids remaining on the filter

were extracted with two, 10 ml portions of hot chloroform.

The extracts were combined and concentrated to about half

the original volume by evaporation. White crystals pre-

cipitated and were removed by filtration and dried in vacuum.





L00
Od


I


-~---


L1








Id
0



kO



r.
0

0

0
d







Srl
F-i

0
4-3









I

0
o
Ha,
.-i
P4-
0

H

a,
cf




I0

. -









M.P. 230-2320 C. Anal. Found: N, 8.9. Calculated for

[(C6H )2PNH2P(NH)-N(NH2)(C6H5)2]C: N, 9.30. The infrared
spectrum of this material was identical with that of

[(C6H5)2P(NH2)-N=P(NH2)(C6H5)2]Cl produced by the
chloramination-ammonolysis of diphenylchlorophosphine.(1)
Yield: 0.42 g (33% of theory based on tetraphenyldiphosphine
used). If the vacuum drying process was not prolonged, the
1:1 chloroform adduct(2) of the substance was obtained.
Anal. Found: N, 7.3. Calculated for

[(C6H )2P(NH2)-N=P(NH2)(C6H )2]Cl CHC13: N, 7.36.
The chloroform-insoluble residue was extracted with

50 ml of hot, 50/50 acetone-ethanol mixture. Addition of
diethyl ether to this solution caused a small amount of
NH4C1 to precipitate. The solution was filtered. Upon
addition of a copious amount of diethyl ether more crystal-
line material precipitated. This material was filtered and
dried in vacuum. M.P. 204-206 C (dec.). Anal. Found:

C, 56.22; H, 5.84; P, 11.78; N, 10.69; Cl, 14.50. Calcu-
lated for [(C6H5)2P(NH2)2]Cl: C, 57.04; H, 5.58; P, 12.26;
N, 11.09; Cl, 14.03. This analysis indicates that the
material may be slightly contaminated with ammonium chloride.
The infrared spectrum of this material (Fig. 9) is con-
sistent for the formulation [(C6H5)2P(NH2)2]C1, and shows
that the amount of ammonium chloride present is too small
to be detected by this infrared technique. Attempts to









S~50






co






0<\ *
pa










0 r
H
0
H4 H P-






















HH*
-4













K-~










synthesize the hexafluorophosphate and tetraphenylborate

derivatives of the diphenyldiaminophosphonium ion by meta-

thesis in water failed. Yield of diphenyldiaminophosphonium

chloride: 0.20 g (14% of theory based on tetraphenyldiphos-

phine used).

The remaining insoluble material was shown to be

ammonium chloride.


The 7 action of the Chloramine-Ammonia Mixture
with Tetraphenylcyclotetraphosphine

In a typical experiment, 0.98 g (2.27 mmoles) of

tetraphenylcyclotetraphosphine was dissolved in 50-75 ml

of dry benzene and exposed to the effluent gases of the

chloramine generator. A white precipitate formed immedi-

ately and the solution grew warm. The reaction was

apparently complete when the temperature of the mixture

dropped to about 200 C because of evaporation of the

solvent. Chloramination was continued for 5-10 minutes

longer to insure exposure of the reactants to an excess of

chloramine and ammonia. The benzene solution was removed

from the precipitate by filtration and the residue was

washed with 25 ml of dry benzene. The filtrate and wash-

ings were combined and evaporated to dryness yielding 0.40 g

of a white, air-sensitive solid. This solid melted to an

opaque liquid at 68-720 C and the melt did not become clear

when heated to above 2000 C. The analytical data for










several samples of this material are summarized in the

table below.

Found C H P N C1 Mol. Wt.

Sample 1 51.85 5.95 17.55 15.40 2.5 940 (in benzene)

Sample 2 20.51 17.15
20.41 17.18(Kjeldahl)

Sample 3 49.74 5.21 21.45 19.20 4.08 870 (in benzene)

The P:N ratio in these samples is 1:2. This implies the

structural unit C6H5 /NH2 and a likely structure

might be

might be


C H5 NH2 C H NH
6 5\ 2 6 5\ / 2
Cl [ P-N ]- PP=-NH
n


where n 5 5 .


The calculated elemental analysis for such a formulation is:

C, 49.94; H, 4.97; P, 21.50; N, 19.42; C1, 4.16; Mol. Wt.

865. The infrared spectrum (Fig. 10) is consistent for

such a structure. Pyrolysis of the crude material at 2000 C

and 0.10 mm Hg produced ammonium chloride as a sublimate and

an intractable residue which had a nitrogen content lower

than the original material.

The benzene-insoluble precipitate was extracted with

50 ml of 50/50 ethanol-acetone mixture. The solution was

removed from the insoluble ammonium chloride by filtration

and a product was precipitated by the addition of copious

amounts of diethyl ether. Upon filtration and drying in

vacuum the crude material was found to melt with decompo-

sition in the range 160-170 C. After recrystallization










53






E-1






PC\ 0




1
,c








00



0r




0 o
(^- P
o

o 0 -









4-,)
HI 0
o ed
a) r-H .-




,- -t --







a o









H



r<
0








U)






H



bO
rc1 *
K1- *
.-^-^^ .--- oj ?-
~~~ -- ---- __________-- ^ 4 ->
-- == r-\
/-- -- M r
-- ~~~c --- ~-c*

^- --- ---- ----










~~^ 0
c^,C 1-1
^"*^- r
_^- ro>









from 50/50 acetone-ethanol, the observed melting point was

164-1650 C. Anal. Found: C, 38.24; H, 6.15; P, 16.37; N,

21.96; Cl, 17.35. Calculated for [(C6H5)P(NH2)3]Cl: C,

37.61; H, 5.79; P, 16.17; N, 21.93; Cl, 18.50. The infrared
spectrum (Fig. 11) is consistent for the formulation

[(C6H5)P(NH2)3]Cl. Attempts to synthesize the hexafluoro-
phosphate and tetraphenylborate derivatives of the phenyl-

triaminophosphonium ion by metathesis in water failed.

Yield: 0.24 g (14% of theory).

The phenyltriaminophosphonium chloride so prepared

was quite sensitive to hydrolysis. Slow recrystallization

of the product from alcohol exposed to the atmosphere pro-

duced the hydrolysis product, C6H5P(O)(NH2)2(92) M.P.

180-1810 C (dec.) (Lit.(91): M.P. 1890 C). Anal. Found:

C, 45.47; H, 5.81; P, 19.86; N, 17.95; 0 (by difference),

10.43. Calculated for C6H5P(O)(NH2)2: C, 46.16; H, 5.81;

P, 19.84; N, 17.94; 0, 10.25. The infrared spectrum of

phenylphosphinic diamide is shown in Figure 12.

Discussion

The results of this study show that under the condi-

tions of our experiment chloramine cleaves the phosphorus-

phosphorus bond in tetramethyldiphosphine, tetraethyldi-

phosphine, tetraphenyldiphosphine and tetraphenylcyclotetra-









55







0






I o

r-N
S0




0

00












oo
,-I





04
co o


I 0



o










HO I








CO-
co
f K\ i-i
\^ CaJ
_^_^---- 't^
C.r 'K'


1






































J
_- -
~~ *~ ~- r


K
r<
r-





r-


c00




rc\

CO


-" I
-I *
-4 0
-4

0
a-


N
>
N >



J:


11
O






P-1
0







0






C)
0
-P





0



I)






(\J


b4D
*o




*H
k-


r;i~------


7


i










phosphine. The chloramination-armonolysis of tetramethyl-

diphosphine yields dimethyldiaminophosphonium chloride as

the only important product. Thus, this reaction appears to

be quite analogous to the chloramination of dimethylchloro-

phosohine.(5,6)

Similarly, the chloramination-ammonolysis of tetra-

ethyldiphosphine gives diethyldiaminophosphonium chloride

in yields which average between 60 and 70 per cent of theory.

Unlike in the chloramination of diethylchlorophosphine,

however, the intermediate, [(C2H5 2P(NH2)-N=P(NH2)(C2H5)2]Cl,

is not produced. On the other hand, a trace of diethyl-

phosphonitrilic triner is observed. It is curious that

only a trace of diethyldiaminophosphonium chloride undergoes

complete condensation,

[(C02 P(2 )]Ci [(C2H5)2PN]3 + 3 NH4C,

while no intermediate product of condensation,

[(C2H5)2P('2)-N=P(NH2)(C2H5)2]C1, is observed. One might

speculate that at some time during this exothermic reaction

the complete condensation could momentarily become

kinetically favored.

The chloramination-ammonolysis of tetraphenyldiphos-

phine is .lot so straightforward and simple as the chlorami-

nation-ammonolysis of tetraalkyldiphosphines. However, it

is clear that cleavage of the phosphorus-phosphorus bond

occurs. The principal product which could be isolated and









identified was the substance,

[(C6H5)2P(NH2)-Y=-P(IH2)(C6H5)2]C1. This was also an impor-
tant product of the chloramination-ammonolysis of diphenyl-
chlorophosphine.(1) A more interesting result is the

identification of [(C6H5)2?P(H2)2]C1 as a product of the

reaction. Diphenyldiaminophosphonium chloride or the di-
phenyldiaminophosphonium ion is the postulated reactive

intermediate(1) in the formation of

[(C6H5)2P(NIH2)-N=P(HH2)(C6H5)2]C1 and [(C6g5)2PN] from

(C6H5)2PC1, NH2C1 and lH3. Unfortunately, the yield of
this material was small and it could not be purified from

traces of ammonium chloride. The substance is soluble in
polar solvents such as alcohol and water but is insoluble

in chloroform and non-polar solvents such as benzene and
n-hexane. Dissolved in water, it gives an immediate test

for chloride ion with Aga. However, it must hydrolyze
rapidly in water for no metathetic derivative of PF6 6 or

(C6H5)4B3 6 could be detected.
A third product which was isolated and identified
was the amide of diphenylphosphinic acid, (C6H5)2P(0)NH2.
This material was characterized by its melting point,

nitrogen analysis and infrared spectrum. It is quite
possible that during its preparation, the starting material,
tetraphenyldiphosphine, became contaminated with the
monoxide, (C6H5)2P-?(O)(C H5)2. This material might undergo










chloramination-ammonolysis giving the amide as one product,

Nh2C1
(C6 5)2-P(O)(6H 5)2 +

[(C6H5)2P(Hm2)2]C1 + H2N-P(O)(C6H5)2

This is an interesting possibility and should be investigated

further.
Alternatively, the amide may arise from the hydrolysis

of diphenyldiaminophosphonium chloride,

[(C6H5)2P(H 2)2]C1 + H20 (C6H5)2P(O)NH2 + NH Cl

Finally, in some experiments an intractable, benzene-

soluble tar was isolated from the chloramination-ammonolysis
of tetraphenyldiphosphine. This material melted at just

above room temperature and contained no chlorine, but still

appeared to be air sensitive, turning wet after a few
minutes exposure to the atmosphere. Some structural

features are evident from examination of the infrared

spectrum (Fig. 8). This spectrum shows N-H stretching and

deformation peaks in the region from 3380 cm-1 to 3180 cm-1

and at 1575 cm-1, respectively. Phenyl C-H stretching
peaks and "C=0" stretching peaks are observed at 3040 cm1
and at 1590 cm-1, 1480 cm-1 and 1439 cm-. A strong, broad
peak is observed at 1260 cm-1 which is characteristic of

"P=N" stretching in phosphonitrilic derivatives. A strong

peak occurs at 1175 cm- a region which is sometimes









associated with the phosphoryl group, P--0. This peak
-1
appears as a shoulder on a strong peak at 1160 cm which

might be attributed to phenyl C-H in-plane bending. A
-l
sharp, strong peak occurs at about 1117 cm This peak is

usually observed in compounds in which the phosphorus atom

is tetracoordinate and bonded to at least one phenyl

group.(74,75) At 921 cm- a peak of medium intensity

occurs which might be assigned to the P-NH-P grouping.(9

A similar peak occurs in the spectrum of

[(C6H 5)2 P(?2)-N=P(NTH)(C6 H 5)2]C.(1) Several sharp peaks
-1
appear in the region of 800-695 cm Peaks in this

region are usually attributed to C-H out-of-plane bending

vibrations in che phenyl groups and to P-phenyl bonds.

The observed molecular weight (450) of this substance is

in the right range for the grouping, [(C6H5 )2-N-P(C6H5)2];

however, the analytical data obtained so far are not help-

ful in completing the characterization of this substance.

The infrared spectra of [(C6H5)2P(NH2)2]C1 and

(C6H )2P(0)RH2 (Figs. 7 and 8) resemble each other closely.
-i
In fact, in the region from 4000 to 1200 cm- very little
difference is noted in the placement and number of peaks

in the two spectra. At 1175 cm- however, the spectrum

of (C6H5)2P(0)THp2 has a strong absorption which is attributed
to the phosphoryl group. This peak is absent in the spectrum

of [(C6H5)2P(NH2)2]C7 The two spectra also differ










considerably in the region from 1105 to 695 cm This

region contains the C-H bending peaks as well as the peaks

attributed to P-phenyl bonding. In general, we can say

that the infrared spectra confirm the identity of these

compounds.

The chloramination-ammonolysis of tetraphenylcyclo-

tetraphosphine produces a material which is apparently a

linear phosphonitrilic derivative. An examination of its

infrared spectrum (Fig. 10) shows a broad N-H stretching
-i
band which peaks at 3210 cm a strong N-H deformation

band which peaks at 1550 cm- a very broad band at 1250-
-1
1155 cm which is very similar to the "P=N stretching
-i
band in phosphonitrilics, and a sharp peak at 1115 cm

which is associated with tetracoordinate phosphorus bonded

to phenyl. In addition the infrared spectrum contains

peaks usually attributed to phenyl C-H stretching and

bending vibrations, "C=C" stretching vibrations and P-phenyl

bonds. Thus, the infrared spectrum is consistent for the

CEH / H
unit, /P The analytical data compiled on several

samples of the same material indicate the same unit since,

in all cases, the P:N ratio was almost exactly 1:2.

The average molecular weight of this material, de-

termined ,ryoscopically on several samples, varied from

750 to 950 indicatin- an average of 5-7 P-N units. The










complete solubility of this substance in solvents such as

benzene and chloroform indicates that the small amount of

chlorine present is not caused by impurities such as

ammonium chloride. Therefore, we postulate that the

chlorine is bonded to the phosphorus atom of the molecule,

perhaps as an end-stopping group. This postulate is sup-

ported somewhat by the broad, infrared peak at 510 cm-

which is in the region of absorptions attributed to the

P-Cl bond. The postulated structure is then,

C6H5 NH C6H5 NH2
6 5 / 2 6 5 / 2
Cl [ --P N -n--- P =NH where the average value of n is 5.

This formulation is supported by infrared and analytical

data as well as by consideration of the physical properties

of the material. Clearly, however, the structure of this

material is still a subject of speculation. Additional

physical and chemical information should be obtained on

this interesting substance. At the time of this writing

a nuclear magnetic resonance investigation was being under-

taken. However, the results of such a study are not yet

available.

The second compound obtained from the chloramination-

ammonolysis of tetraphenylcyclotetraphosphine was identified

as phenyltriaminophosphonium chloride, [(C6H5)P(NH2)3]Cl.

Although this material could not be isolated in absolute

purity from ammonium chloride, there is little question of










its identity. The infrared spectrum (Fig. 11) contains the

usual N-H stretching and deformation peaks and the peaks

associated with phenyl C-H bonding, phenyl "C=C" bonding

and P-phen;l 'onding. A strong peak is observed at

1135 cm-1 which is attributed to tetracoordinate phosphorus

bonded to phenyl. The absence of peaks in the region from

1300 cm1 to 1150 cm1 indicates that the material has

neither a condensed P-N=P structure, nor is it contaminated

with the amide, C6H5P(0)(NH2)2. The amide was synthesized

easily from phenyltriaminophosphonium chloride by exposing

a solution of the chloride in alcohol to moist air. Indeed

the infrared spectrum of the amide (Fig. 12) is quite

similar to that of phenyltriaminophosphonium chloride.
-i
However, it contains a sharp peak at 1155 cm attributed

to the phosphoryl group.

Although portions of this study are incomplete,

there are certain results which are significant. We can

now state that chloramine cleaves the phosphorus-phosphorus

bonds in substituted diphosphines and in tetraphenylcyclo-

tetraphosphine. Although other reaction sequences may be

possible, we feel that the first step in the chloramination

of diphosphines involves the formation of an aminophosphine

and a chlorophosphine,


R2P-PR2 + :`2 01 R2PNH2 + R2PCl .










This step is analogous to the first step in the reaction of

certain diphosphines with methyl iodide (Chapter II), and

is analogous to the first step in the halogenation of di-

phosphines. The aminophosphine and the chlorophosphine

could then undergo further chloramination and ammonolysis

to produce the observed products.

This study has provided a convenient new method for

the synthesis of dialkyldiaminophosphonium salts. Previ-

ously, these derivatives were synthesized from dialkyl-

chlorophosphines which are obtained with some difficulty.

For example, instead of using dimethylchlorophosphine which

has a short shelf-life and must be used as soon as it is

obtained, we can now utilize tetramethyldiphosphine which

can be stored indefinitely and used when desired. The

convenience of this method for the preparation of dialkyl-

diaminophosphonium chlorides will be further appreciated

in the discussion of Chapter IV which deals with the

condensation reactions of these salts.

This method seems to favor the formation of diamino-

phosphonium salts. Thus, using tetramethyldiphosphine and

teoraethyldiphosphine, the corresponding diaminophosphonium

salt was either the only product or the major product of

the reaction. Chloramination-ammonolysis of diethylchloro-

phosphine, on the other hand, produces only a 20 per cent

-ield of the diaminophosphonium salt. Tetraphenyldiphosphine











gives diphenyldiaminohsphophonium chloride, a material which

was a postulated product in the chloramination of diphenyl-

chlorophosphine but was never isolated. Likewise, tetra-

phen'lcyclotetraphosphine produces phenyltriaminophosphonium

chloride.

In view of the possible value of diamino- and tri-

aminophosphonium salts as phosphonitrilic precursors

(see Chapter IV), we feel that this reaction should be

applied to a number of other diphosphines and polyphos-

phines. This would indicate the generality of the method

and possibly make available a variety of diamino- and

triaminophosphonium salts for further investigation. Some

poly hosphines which should be chloraminated are (CF-P)

and (2P)x where R is an alkyl group. It would also be

interesting to examine the reaction of chloramine with

amino-substituted diphosphines such as C6H5(R2N)P-P(R2N)C6H5

and (R2N)2P-P(R2N)2.


Summary

Chloramination-ammonolysis of tetramethyldiphosphine

and tetraethyldiphosphine produces dimethyldiaminophos-

phonium c' ride and diethyldiaminophosphonium chloride in

good yields, and produces traces of diethylphosphonitrilic

trimer. These materials were identified by chemical

analysis and by comparison of their infrared spectra and











melting points with those of the authentic materials pro-

duced by oth.- methods.

The chloramination-ammonolysis of tetraphenyldi-

phosphine produces a new compound, diphenyldiaminophos-

phonium chloride, and its postulated condensation product,

[(C6H5)2P(NH2)-N=P(NH2)(C6H )2]Cl. In addition, the amide,

(C6H5)2P(0)IH2, and an unresolved tar were produced in the

reaction.

Chloramination-ammonolysis of tetraphenylcyclotetra-

phosphine produces a material tentatively identified as
C -H NH CF ?,-K
o6 / 2 o6- / 2
Cl- [ --N ]n P--NH where the average value of n is 5.

This reaction also produced a new compound, phenyltriamino-

phosphonium chloride. The identity of this material was

established by elemental and infrared analysis and by

synthesis of a derivative, C6H5P(O)(NH2)2.

Infrared data are presented and interpreted in terms

of the structures of the compounds synthesized in this

study.

The chemical evidence leads to the conclusion that

the chloramination of diphosphines and polyphosphines causes

cleavage of the phosphorus-phosphorus bonds. Further

chloramination and ammonolysis of the fragments produces

the same materials which arise from the chloramination of

2PC12 or R2PCl compounds. This reaction constitutes a new








67


method for the production of d.amino- and triaminophos-

phonium chlorides. In this connection, the reaction is

more convenient than th. one which employs chlorophosphines

because diphosphines and polyphosphines are easier to

prepare and store.












CHAPTER IV


THE PYROLYTIC CONDENSATION OF DIALKYJLDIAIINOPHOSPHONIUM
CELORIDES AOD CF L(C2H5)2P(Ih 2)-N=P(NH2)(C2 H5)2]Cl


Experimental


Nanioulation of materials.-The aminophosphonium

salts used in this study were sensitive to atmospheric

moisture, deliquescing and subsequently hydrolyzing after

only a few minutes exposure. Therefore, the starting

materials were stored and transferred in a D. L. Herring

Hoael HE-43 Dri Lab equipped with a Model HE-93 Dri Train.

The products of the condensation reactions were usually

unreactive to moist air. However, in certain cases the

products were hygroscopic in air. These materials were

dried in a vacuum desiccator and stored in sealed vials in

the desiccator.

Benzue and petroleum ether were obtained as reagent

grade materials and were dried and stored over calcium

hydride. Tri-n-butylphosphine was obtained from Food

Machinery and Chemical Corporation and used as obtained.

Phosphorus trichloride was obtained as the reagent grade

material and used as obtained. All solvents and liquid

reagents were transferred by pipette to minimize exposure

to moisture.











Met-hos of analysis.- elemental analyses were per-

formed by Galbraith Laboratories, Inc., Knoxville,

Tennessee. Some nitrogen analyses were also obtained using

a Coleman :Iodel 27 nitrc-en analyzer.

:Molecular weights were determined either by the

cryoscopic method in benzene, or in benzene or chloroform

solution using a :Kecrolab Vapor Pressure Osmometer.

The infrared spectra of materials synthesized in

this study were recorded on a Beckmann Model IR-10 spectro-

photometer. Solid samples were either mulled with Nujol,

pressed into KBr disks, or melted on KBr plates and

examined as thin films when the melting point was below

1000 C. A summary of the spectral bands of new materials

produced in this study between 3.4 and 30 microns is found

in ;.1ble 6.

Kelting points were obtained in capillary tubes

using a Thomas-Hoover capillary melting point apparatus.

Preparation of dialkyldiaminoDhosphonium chlorides

and [(C 2H52P( 2)-N=P(I'H2)(C2H5)2]Cl.-In the early stages

of this investigation, dimethyldiaminophosphonium chloride

and diethyldiaiinophosphonium chloride were prepared by the

chloramination-ammonolysis of dimethylchlorophosphine and

diethylchlorophosphine,() respectively. However, soon

after this investigation was begun, a more convenient method

was found, namely, the chloramination-ammonolysis of










TABLE 6(a)

INFRARED ABSORPTION DATA (Cm-1

[(CH )2::]n, KBr disk

2975(m), 2900(m), 1410(m), 1290(s), 1270(s), 1200(s,sh),
1160(vs), 1010(w,sh), 965(m), 940(m), 915(s),
880(s), 855(vs), 751(m), 720(s), 685(m),
650(w), 560(m), 490(m), 420(s), 368(w).

[(n-CqH9)2 P]3 melt

29'5(s), 2920(s), 2855(m), 2300(w,b), 1459(w),
1450(w), -GO(w), 1362(w), 100(w), 1260(w),
1224(:i), 1155v"-s), 1085(w), 1045(w,sh),
c1000(,b), 95-(wI ), 913(w), 889(w), 785(w),
719(m), 660(m,b), 505(w), 280(vs,b).

s(a) strong; m,medium; w,weak; b,broad; v,very;
sh, shoulder.










tetramethyldiphosphine and tetraethyldiphosphine. This

method of preparation is discussed in detail in Chapter III.

Substance, [(C2H5)2P( N: 2)-N=P(NH2)(C2H5)2]C1,

was prepared by the chloramination-ammonolysis of diethyl-

chlorophosphine.) It was also obtained as a product of

the condensation of dieth:ldiaminophosphonium chloride.

Di-n-butyldiaminopospsphonium chloride was synthesized

by the chloramination of di-n-b ylchlorophosphine.5)

This chlorophosphine was conveniently prepared by the method

of V. t. Plets(4) which involves the decomposition of tri-

butyldichlorophosphorane

(C H)PC2 (C4H9)2PC1 + C ,Cl

Tributyldichlorophosphoranc can be readily synthesized by

the reaction of triburylphosphine with PC1:(87)

3(C4 9g)P + 2 PCl -3(C4H9) PC12 + 2 Px

In a typical experiment, 2.91 ml (33.3 mmoles) of phosphorus

trichloride was dissolved in about 50 ml of dry benzene and

placed under nitrogen in a Minilab reaction flask (Fig. 5).

To this solution, 11.3 ml (50 mmoles) of tri-n-butylphosphine

was added dropwise with stirring under a slow flow of dry

nitrogen gas. The solution rapidly became deep, orange-red

in color arn heat was evolved. Near the end of the addi-

tion an oran- -red, amorphous solid suddenly precipitated

from the mixture. At the end of the addition the mixture







72

was stirred vigorously until it had cooled to room tempera-

ture (250 C). The benzene solution was removed from the

precipitate by filtration and the precipitate was washed

with 1-2, 25 ml portions of dry benzene and filtered, care

being taken not to expose the solution to atmospheric

moisture. The filtrate and washings were combined and

evaporated to dryness in vacuum. The white, crystalline

product, (C4H9)3PC12, was obtained in almost quantitative

yield. This material was transferred in the dry box to a

200 ml round bottomed distillation flask and heated under

an atmosphere of nitrogen at about 1400 C. Butyl chloride

distilled from the mixture (b.p. 780 C) and some HC1 was
evolved. When the distillation of butyl chloride had

ceased (1-5 hours) the mixture was cooled and distilled

under vacuum. The product distilled at 570 C and 0.1 mm Hg

(Lit.,6): b.p. 0.25 = 39-470 C). The yield of dibutyl-

chlorophosphine by this method was usually over 50 per cent

of theory based on the amount of (C4H9)3PC12 used.

The Pyrolytic Condensation of Dimethyldiaminophosphonium
Chloride

n[(CH )2P(NH2)2]Cl [(CH3)2PN]n + n NH4Cl

n = 3,4, higher
In a typical experiment, 1.15 g (8.9 mmoles) of

dimethyldiaminophosphonium chloride was placed in a semi-

micro sublimation apparatus (Fig. 15) and heated at about

















































Fig. 13.-Semimicro Sublimation Apparatus.









2000 C and 0.2 mm Hg for three days. The resulting subli-

mate was removed from the cold finger under nitrogen and

extracted with several portions of hot, 30-600, petroleum

ether. The residue from this extraction was identified as

ammonium chloride. Evaporation of the petroleum ether

yielded a white, crystalline material with a melting range

of 160-1700 C. Anal. Found: C, 31.83; H, 7.98; P, 41.15;

N, 18.73. Calculated for [(CH )2PN]: C, 32.01; H, 8.06;

P, 41.28; N, 18.66. Crude yield: 0.55 g (82% of theory).

The mixture was separated into almost equal amounts of

dimethylphosphonitrilic trimer and tetramer(26) by

fractional crystallization from petroleum ether. The

molecular weights (cryoscopic in benzene) were 220 (calcu-

lated: 225) and 311 (calculated: 300), respectively. The

trimer melted with sublimation at 187-1900 C (Lit:(26) M.P.

195-196 C) and the tetramer melted with sublimation at 157-
1600 C (Lit:(26) M.P. 163-1640 C). The infrared spectra of

these compounds agree with the assignments reported by

Searle.(26)

The Synthesis of Highly Polymeric Dimethylphosphonitrile

In several pyrolyses of dimethyldiaminophosphonium

chloride, described above, a trace of a black, glassy

residue was observed in the sublimation pot at the com-

pletion of the sublimation of ammonium chloride and

[(CH )2PN] ,4. This material melted in the range of 156-

1460 C and was not visibly sensitive to moist air. Anal.










Found: C, 51.81; H, 8.16; N, 18.79; P, 41.14; Mol. Wt., 7640

(Mol. Wt. of a (CH3)2PN-unit, 75). Thus, it was discovered

that the pyrolytic condensation of dimethyldiaminophos-

phonium chloride produces trace amounts of [(CH )2PN]n where

n is a large number. The yield of high polymer could be

increased considerably by mixing the starting phosphonium

salt with finely divided ammonium chloride produced by the

gas phase reaction of chlorine and ammonia. In a typical

experiment the phosphonium salt and a weighed amount of

ammonium chloride were thoroughly mixed in the dry box,

placed in a semimicro sublimation apparatus and pyrolyzed

as before. The dimethylphosphonitrilic trimer and tetramer

and ammonium chloride sublimed to the cold finger and were

separated as before. The high polymer remained in the

sublimation pot and was either scraped from this vessel or

removed by dissolving it in benzene. The effect of ammonium

chloride on the distribution of products of this reaction

is shown in Table 7. The infrared spectrum of the crude

polymer is shown in Figure 14.

The high polymers so formed were usually soluble in

hot benzene and chloroform. In some cases a residue was

observed which swelled in benzene but did not dissolve.

Extraction(95) of the crude material with cyclohexane pro-

duced, upon evaporation of the solvent, a white powder

melting at 139-1460 C and having a molecular weight of from











TABLE 7

EFFECT OF AMMONIUM CHLORIDE ON PRODUCT DISTRIBUTION


Wt. % of NH Cl in


Recovered


Recovered


Starting Material Yield of Polymer, Yield of [(CH )2PN]5 4
_%% 5> d 4


0

trace

trace


4.5

4.2

6.9


5.6

9.9
10.4

17.4


13.6


14.4


20 11.2 68










































r-I

o



aD






cd


c'J
v
I-I



CM

0


^-p




I-)
aO













-d










3500 to 9000 depending on the sample used. The residue from
the cyclohexane extraction was soluble in benzene, melted

at 136-1380 C and had a molecular weight of 12,500.

Thermal gravimetric analysis(95) (using an Aminco

Thermograv, American Instrument Co.) of a sample with an

average molecular weight between 8000 and 9000 was obtained

using a 100 cc/min flow of helium at a rate of temperature

increase of 3/min. This analysis showed no weight loss up

to 300 C, and a rapid loss of weight from 500 to 5000 C
during which essentially all of the sample sublimed from
the apparatus as low-molecular-weight cyclic material,

principally trimer and tetramer.
Differential thermal analysis was carried out on

this material(95) in helium using a heating rate of 3/min

with A1203 as a reference. A sharp endotherm was observed

at 1420 C (M.P. of sample: 143-1450 C) and a broad exotherm

was observed starting at about 300 C, the latter presumably

resulting from the onset of thermal decomposition.

The Pyrolytic Condensation of Diethyldiaminophosphonium
Chloride

2[(C2H )2P(NH2)2]Cl [(C2H5)2P(NH2)-N=P(NH2)(C2H5)2]Cl
+ NH4Cl

[(C2H5)2P(NH2)2]Cl + [(C2H5)2P(NH2-N=P(NH2)(C2H5)2]Cl


- [(C2H )2PN]3 + 2 NH C1










In a typical experiment, 0.99 g (6.5 mmoles) of di-

ethyldiaminophosphonium chloride was placed in a semimicro

sublimation apparatus and heated to about 1800 C and 0.2 mm

Hg for five days. This process produced a white sublimate

as well as a substantial amount of light-colored residue.

The residue was dissolved in boiling benzene and filtered.

Upon evaporation of the benzene a white, crystalline

material was recovered which melted at 61-64 C; yield,

0.30 g. This material is hygroscopic, water-soluble and
gives a Cl- test with aqueous AgNO,. Anal. Found: N, 16.5.

Calculated for [(C2H5)2P(NH2)-N=P(NH2)(C2H5)2]C: N, 16.18.

The infrared spectrum of this material was identical with

that of [(C2H5)2P(NH2)-N=P(NH2)(C2H5)2]C1 (M.P. 58-610 C)

produced by chloramination-ammonolysis of diethylchloro-

phosphine.5) The nuclear magnetic resonance data for

[(C2H5)2P(NH2)-N=P(NH2)(C2H )2]C1, not included in the
earlier reference, 5) provides some interesting additional

information about the structure of this substance. The

proton magnetic resonance spectrum (Fig. 15) was run on a

Varian high resolution spectrometer at 56.4 Mc using a

CDC13 solution. The spectrum was obtained by sweeping

slowly through the field and interchanging the reference,
acetaldehyde, with the sample. Peak A refers to the NH2

protons, peak B to the methylene protons and peak C to the

methyl protons. The usual methylene quartet and methyl












80











fr-
0
r-i
i-J

Lf

cuj




































LJ


4
)
_ __ _ **"==; --

^ -^. 0

====-----^
----- : -z= ^ *
-- .-^ ^-



'-^ m ^-


~~3











triplet are further split by spin-spin coupling with the

phosphorus atoms. The spectrum is consistent with the

NH NH2
S2 2
structure(1) C2H5 P N PC2HH5 j C.
C2H5 C2H5

Approximate P values and average chemical shift values are

listed in Table 8.

TABLE 8

N. M. R. SPECTRAL DATA FOR [(C2H5)2P(NH2)-N=P(NH2)(C2HS)2]C1


Group Chemical Shift,T Coupling,
c.p.s.

NH2 5.18 H-H 8

CH2 7.98 (ave.) P-CH2 14

CH3 8.75 (ave.) P-CH3 18


The ratio of areas under the NH2 peak to those under

the CH2 and CH3 peaks is approximately 1:5. When the

nuclear magnetic resonance spectrum was run at 19.3 Mc

a single, broad peak for phosphorus was observed corres-

ponding to a chemical shift of 41 p.p.m. to low field in

comparison to 85 per cent phosphoric acid.

The sublimate was dissolved in benzene and filtered

to remove ammonium chloride. The benzene was removed by

evaporation and the resulting white, crystalline material









was carefully resublimed at about 500 C and 0.1 mm Hg. The
sublimate melted at 109-1120 C. Anal. Found: C, 46.39; H,
9.92; P, 30.30; N, 15.49; Mol. Wt. 305. Calculated for
[(C2H5)2PN] : C, 46.60; H, 9.78; P, 30.04; N, 13.59; Mol.
Wt. 309. Yield: 0.21 g (33% of theory). The infrared
spectrum of this material agreed with the assignments listed
in the literature(25) for diethylphosphonitrilic trimer.
The literature value for the melting point of the trimer is
117.5-1190 C.
The residue from this sublimation was recrystallized
from benzene and identified as the intermediate,
[(C2H5)2P(NH2)-N=P(NH2)(C2H5)2]C1. The total yield of this
intermediate was 0.54 g (41% of theory).

The Pyrolytic Condensation of
[(C2H5)2P(NH2)-N=P(NH2) (C2H5)2]C1


[(C2H5)2P(NH2)-N=P(I2)(C25)2]C1 -[(C2H5)2PN],4 + NH4C

In a semimicro sublimation apparatus, 0.85 g (3.5
mmoles) of (C2H5)2P(NH2)-N=(NNH2)(C2H5)2]Cl was heated at
about 2000 C and 0.15 mm Hg for 4-5 days. This process
produced a white, oily sublimate and a trace of black re-
sidual ash. The sublimate was extracted with several
portions of petroleum ether. The residue from this extrac-
tion was again extracted with several portions of hot











benzene. From the benzene solution, 0.25 g (0.96 mmoles) of

unreacted starting material was recovered. From the

petroleum ether solution, 0.36 g (75% of theory based on the

starting material actually reacted) of a mixture of di-

ethylphosphonitrilic tetramer and trimer was recovered by

evaporation. The final residue of the solvent extractions

consisted of ammonium chloride.

The mixture of diethylphosphonitrilic tetramer and

trimer was separated by repeated fractional sublimation at

530 C and 0.1 mm Hg. By this method the mixture was found
to consist of about 20 per cent trimer (M.P. 110-1140 C)

and 80 per cent tetramer (a viscous oil 25). Anal. Found:

C, 46.36; H, 9.76; P, 29.84; N, 13.30; Mol. Wt. 401.

Calculated for [(C2H5)2PN]4: C, 46.60; H, 9.78; P, 30.04;

N, 13.59; Mol. Wt., 412. The infrared spectrum of this

material agrees quite well with the assignments listed in

the literature(25) for diethylphosphonitrilic tetramer.

The Pyrolytic Condensation of Di-n-butyldiamino-
phosphonium Chloride

3[(n-C4H9)2P(NH2)2]C1 [(n-C4H9)2PN] + 3 NH4C1

Di-n-butyldiaminophosphonium chloride (1.08 g or 5

mmoles) was placed in a semimicro sublimation apparatus and

heated at 1900 C and 0.1 mm Hg for four days. A white

sublimate was observed. Only a trace of black residue










remained in the pot at the completion of the reaction. The

sublimate was extracted with 30-600 petroleum ether. The

insoluble residue was shown to be ammonium chloride. Evapo-

ration of the petroleum ether yielded a white wax which

melted at 45-500 C and sublimed readily at 70 C and 0.1 mm

Hg. Anal. Found: C, 60.09; H, 11.37; P, 19.23; N, 8.90;

Mol. Wt., 470. Calculated for [(C4H9)2PN]3: C, 60.35; H,

11.40; P, 19.45; N, 8.80; Mol. Wt., 478. Yield: 0.77 g

(95% of theory). The infrared spectrum of dibutylphospho-
nitrilic trimer is shown in Figure 16.


Discussion


The results of this study show that diaminophosphonium

chlorides can be easily converted by pyrolytic condensation

to phosphonitrilic derivatives. The yields observed in such

a process are essentially quantitative.

The pyrolytic condensation of dimethyldiaminophos-

phonium chloride produces amounts of dimethylphosphonitrilic

trimer and tetramer. These compounds were separated from

the byproduct, ammonium chloride, by their solubility in

petroleum ether, and the trimer/tetramer mixture was sepa-

rated by fractional crystallization from petroleum ether.

The materials were identified by elemental analysis, molecu-

lar weight determinations and comparison of their infrared

spectra with published infrared data.(26) When finely










85


O
O
-t

O



0










CO
0






-0
o0 I
OON





O 1
0H 0


r- 0 ~


S0 -P
-H 01 0



rd
0 0)
O cd
O
S0 nI

H L



b

.r 1










divided ammonium chloride was mixed with the starting

material, pyrolysis produced a new compound identified as

highly polymeric dimethylphosphonitrile. This material is

CH CH
r 3, / 3
a polymer of the formula,[ P-----N--n where n varies

from 50 to 150. It was characterized by elemental analysis,

molecular weight determinations, infrared analysis, thermal

gravimetric analysis and differential analysis. The infra-

red spectrum of this material (Fig. 14) is somewhat similar

to that of the cyclic trimer or tetramer having C-H stretch-

ing and deformation peaks at 2970 cm1 and at 1410 cm-1
-i
respectively. Two peaks occur at 1290 and 1270 cm1 which

are attributed to P-CH3 bonding. (26) The "P=N" stretching

band exhibits a broad, strong shoulder at about 1200 cm1

and a strong peak at 1160 cm- There are several peaks in

the region from 850 cm1 to 965 cm1 and from 685 cm- to

755 cm-1. Peaks in this region are generally attributed to

"P=N" elongation and "P-N=P" deformation.(24'25) Definite

assignments for these peaks cannot be made at the present

time. Yields of the polymer as high as 32 per cent of

theory were obtained when mixtures of about 10 per cent

finely divided ammonium chloride and 90 per cent dimethyl-

diaminophosphonium chloride were pyrolyzed.

The pyrolytic condensation of diethyldiaminophos-

phonium chloride produces the primary condensation product,










[(C2H5)2P(NH2)-N=P(NH2)(C2H5)2]Cl which was recovered in
about 40 per cent yield, and diethylphosphonitrilic trimer,

[(C2H5)2PN]3 which was recovered in about 30 per cent yield.
The first condensation product was shown by elemental

analysis and infrared analysis to be identical with

[(C2H5)2P(NH2)-N=P(NH2)(C2H5)2]Cl produced by the chlorami-
nation-ammonolysis of diethylchlorophosphine. 5 Diethyl-

phosphonitrilic trimer was identified by elemental analysis,

molecular weight determination and comparison of its infra-
(25)
red spectrum with published infrared data. 25

The pyrolytic condensation of the intermediate,

C(C2H5)2P(NH2)-N=P(NH2)(C2H5)2]C1, produces a mixture of
diethylphosphonitrilic trimer and tetramer which was re-

covered in about 75 per cent yield. The phosphonitrilic

mixture, consisting of about 80 per cent tetramer and 20

per cent trimer, was separated from the byproduct, ammonium

chloride, by its solubility in petroleum ether. The trimer

and tetramer were then separated from each other by repeated,

fractional vacuum sublimation. In this case, the trimer was

slightly more volatile than the tetramer and a separation

could be made.

The pyrolytic condensation of di-n-butyldiamino-

phosphonium chloride produces a nearly quantitative yield

of a new material identified as di-n-butylphosphonitrilic

trimer, [(n-C4H9)2PN]3. This material was characterized by










elemental analysis, molecular weight determination and infra-

red analysis. The infrared spectrum of this material (Fig.

16) has the usual C-H stretching and deformation peaks in

the region of 2950-2850 cm1 and 1450-1370 cm- respec-

tively.. Bands attributed to skeletal -CH2- vibrations occur

at 1400 cm-1 1500 cm1 and at 1260 cm-1. A sharp peak is

observed at 1215 cm-1 which may be attributed to P-C bonding.
-1
The "P=N" stretching peak occurs at 1155 cm Of all the

phosphonitrilic derivatives for which this peak has been

measured, it occurs at the lowest energy in this derivative.

This is to be expected because the butyl groups have little,

if any, electron attracting ability. Thus, they are unable

to cause appreciable delocalization of the nitrogen lone-pair

electrons into the region of the P-N bond. The remainder of

the spectrum between 1155 cm-1 and 650 cm-1 contains several

peaks of weak intensity, some of which may be attributed to

skeletal vibrations of the butyl groups. Others lie in the

region assigned to "P=N" deformation peaks, "P-N=P" stretch-

ing peaks and ring breathing vibrations. We can make no

definite assignments in this region at this time.

This study establishes the fact that dimethyldiamino-

phosphonium chloride, diethyldiaminophosphonium chloride,

di-n-butyldiaminophosphonium chloride and

[(C2H5)2P(NH2)-N=P(NH2)(C2H5)2]C1 are convenient phospho-

nitrilic precursors, giving excellent yields of cyclic










phosphonitrilics under pyrolytic conditions. Combined with
the findings of Chapter III, this study constitutes an
important part of a new method of synthesis of such deriva-
tives from substituted diphosphines, chloramine and ammonia.
The results of this investigation have provided very
convincing evidence in favor of the step-wise reaction se-

quence postulated(1) earlier in which the then unknown
diaminophosphonium ion, R2P(NH2)2(, was considered to be
a reactive intermediate leading to phosphonitrilic
derivatives. The case in point is the pyrolysis of di-
ethyldiaminophosphonium chloride. The only products of
this reaction are [(C2H5)2P(NH2)-N=P(NH2)(C2H5)2]Cl and
[(C2H5)2PN]3. Indeed, these are the expected products if
one assumes the following sequence

2[(C2H5)2P(NH2)2]Cl [(C2H5)2P(NH2)=N-P(NH2)(C2H5)2]Cl

+ NH4Cl

[(C2H5)2P(NH2)2]1C + [(C2H5)2P(NH2)-N=P(NH2)(C2H5)2]Cl

[(C2H5)2PN]3 + 2 NH4Cl

The pyrolysis of the intermediate,
[(C2H5)2P(NH2)-N=P(NH2)(C2H5)2]C1, produces chiefly diethyl-
phosphonitrilic tetramer. Some cleavage of the intermediate
does occur, however, resulting in the formation of diethyl-
phosphonitrilic trimer and some decomposed material.










One of the most interesting results of this study

was the discovery and characterization of highly polymeric

dimethylphosphonitrile. This discovery has attracted

interest for several reasons. First of all, despite all

the previous work in phosphonitrilic chemistry, there is a

paucity of information concerning the synthesis of thermally

stable and unreactive high polymers with the repeating unit

R R
---PP=N--- (See Chapter II). This method of synthesis is

one of the few which results in a phosphonitrilic high

polymer which is soluble in common solvents, which can be

molded mechanically and which is relatively unreactive

toward moisture and oxygen.

In addition to exciting academic interest, this

method may also prove valuable in the synthesis of com-

mercially useful polymers. Although the polymeric material

synthesized in this study has some disadvantages in its

ready solubility, low melting point and thermal instability

above 3000 C, films of the substance can be cast which have

reasonable strength.(95) The dimethylphosphonitrile is
CH CHO
isoelectronic with dimethylsiloxane, --- Si--- 0-4-, the

basic unit of an inorganic polymer system which has enjoyed

such wide use in recent years that its parent, (CH )2SiC12,

is now produced commercially in large quantities. If the

isoelectronic relationship is any indication of chemical











and physical similarities which may exist in these two

systems of inorganic polymers, then there is a possibility

that the process discovered in this study may become com-

mercially important in the future.

It is interesting to note that the yield of high

polymers from the pyrolysis of dimethyldiaminophosphonium

chloride seems to depend on the amount of ammonium chloride

mixed with the starting material (Table 7), under similar

conditions of temperature, pressure and time. The postu-

lated first step of the condensation process,

2[(CH )2P(NH2)2]C1 [(CH )2P(NH2)-N=P(NH2)(CH3)2]C1

+ NH4Cl ,

has been confirmed in the pyrolysis of diethyldiaminophos-

phonium chloride. Since the actual mechanism of condensa-

tion is not clearly known, any statement concerning the

mechanism of the effect of ammonium chloride on the first

step or subsequent intermolecular condensations would be

highly speculative.

However, in view of the fact that the cyclic di-

methylphosphonitriles are weak bases,(19) it is conceivable

that in the molten reaction mixture a proton transfer could

occur between ammonium chloride and a ring nitrogen. This

could result in the breaking of a P-N bond and the formation

of a =P species which could attack other ring-nitrogen










atoms and lead to linear products. For instance, the attack

could occur on a cyclic trimer


:N N:
Rj ,R + H @

R N


:N N:H


R N


R R R R
HN===P-N= =P 0


R R
R R R R J P
HN=P=P-N- -P ( + :N N:
RI I/R

RP N/ R


R R R R
R \ / R \ /
- HN=P--N P ,

etc.


This is similar to the mechanism postulated by Allcock and

Best(52) for the polymerization of [PNC12]3 4 (see page 21).

The polymer formed is not highly cross-linked and therefore

undergoes almost complete depolymerization to cyclic deriva-

tives in the 300-5000 range.

There are two suggestions which we can make for

further work in this area. Both suggestions are concerned

with the formation of high polymers. The effect of ammonium

chloride on the pyrolytic condensation of diaminophosphonium

chlorides was investigated only in the case of dimethyl-

diaminophosphonium chloride. This effect should be studied




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SYNTHESIS AND SOME REACTIONS OF SOME DIAMINOAND TRIAMINOPHOSPHONIUM CHLORIDES By STEPHEN EARL FRAZIER A DISSERTATION PRliSl-NTED TO THE GRADUATE COUNCIL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY Ol" TLORIDA December, 19<'i5

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ACKNOWLEDGMENTS The author takes this opportunity to express his sincere gratitude to his research director, Dr. Harry H. Sisler. Although busy with administrative responsibilities, Dr. Sisler has always provided enthusiastic encouragement and offered valuable suggestions and advice concerning this research. Dr. Sisler has also listened sympathetically to the author's personal problems, and has been helpful in obtaining the solutions to these problems. The author wishes to recognize the interest given by the other members of his committee and to thank them for their assistance in preparing this dissertation. A special note of appreciation should go to Dr. D. S, Payne for the many valuable discussions ajid suggestions shared during his visit at the University of Florida. The author also wishes to acknowledge the help of his colleagues, Dr. Donald F. Clemens and Mr. Robert L. McKenney. A note of thanks goes to Mrs. Thyra Johnston who took a personal interest in the typing of this dissertation. Finally, the author wishes to thank W. R. Grace and Company for the generous financial support of this work. 11

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TABLE OF CONTENTS Page ACKNOWLEDGMENTS ii LIST OF TABLES v LIST OF FIGURES vi CHAPTER I. INTRODUCTION 1 II. HISTORICAL BACKGROUND 4 Pliosphonitrilic Derivatives. ....... ^ The Chloramination Reaction 28 III. REACTION OF THE CHLORAMINE-AMNONIA MIXTURE WITH SUBSTITUTED DIPHOSPHINES AND TETRAPHENYLCYCLOTETRAPHOSPHINE 32 Experimental 32 Discussion 5^ Summary 65 IV. THE PYROLYTIC CONDENSATION OF DIALKYLDIAMINOPHOSPHONIUM CHLORIDES AND OF [(C2H^)2P(NH2)-N=P(NH2)(C2H^)2]C1 68 Experimental 68 Discussion 8^ Summary 93 V. THE REACTION OF DIALKYLDIAMINOPHOSPHONIUM CHLORIDES WITH TRI-, TETRA-, AND PENTACHLOROPHOSPHORANES 95 Experimental 95 iii

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CHAPTER Page Discussion 115 Summary 125 VI. GENERAL CONCLUSIONS AND SUMMARY 125 BIBLIOGRAPHY 131 BIOGRAPHICAL SKETCH 137 iv

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LIST OF TABLES Table Page 1. Average P-N Bond Energy in (PNClp) 8 2. Base Strength of Phosphonitrilic Derivatives Toward Protons in Nitrobenzene and Water. ... 14 3. Variation of P-N Stretching Frequency with Electronegativity of Exocyclic Groups 15 4. Phosphonitrilic Derivatives Synthesized from imoi^lj^ 4 18 5. Infrared Absorption Data (Cm" ) 5^ 6. Infrared Absorption Data (Cm ) 70 7. Effect of Ammonium Chloride on Product Distribution 76 8. N. n. R. Spectral Data for [(C2H^)2P(NH2)-N=P(NH2)(C2H^)2]C1 81 9. Infrared Spectral Data, Cm""'97

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LIST OF FIGURES Figure Page 1. Overlap of N Orbitals with P, Orbital . . 9 P^ xz 2, Pi-Electron Energy Levels of CgH^, (PNCl2)x and (PNCl2)i^ 10 5. Overlap of P, -Orbitals with N -Orbitals . . 11 71 ^z ^. Localized, Three-Center P-N-P Bonds in a Phosphonitrile Segment 11 5. Minilab Reaction Flask $8 6. The Chloramine Generator ^1 7. Infrared Spectrum of (G^Ea^) ^^Wmi^ (Nujol) . 46 8. Infrared Spectrum of Intractable Chloramination Product of (C^H^)2P-P(C^H^)2 (Melt). . . 48 9. Infrared Spectrum of [(CgH^)2P(NH2)23Cl (Nujol) 50 10. Infrared Spectrum of Intractable Ghloramination Product of (C^H^P)^ (Thin Film) 53 11. Infrared Spectrum of [(GgH^P(NH2)3]Cl (Nujol) 55 12. Infrared Spectrum of GgH^P(O) (1^2)2 (Nujol) . 56 13. Semimicro Sublimation Apparatus 73 14. Infrared Spectrum of C(GH,)2PN]^(KBr) .... 77 15. H' N.M.R. Spectrum of [(G2H^)2PCNH2)-N=P(NH2)(G2H5)2]C1 80 16. Infrared Spectrum of [(n-G^H^)2PN] ^ (Melt). . 85 vi

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Figure Page 17. Infrared Spectrum of CH^PCl^ (Nujol) 102 18. Infrared Spectrum of (CH^)2PC1, (Nujol). . . . 105 19. Infrared Spectrum of (CH,)2C1^P,N, (Nujol) . . 105 20. Infrared Spectrum of {:iG2B..')2^^'^'^2^^-^2 ^^^)' ^^^ 21. Infrared Spectrum of Suspected [(CH,)2PN'CH^C1PN]^ (Thin Film) 112 vii

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CHAPTER I INTRODUCTION In recent years an area of study dealing with the synthesis of phosphonitrilic derivatives and precursors has been under investigation in our laboratories. Our interest in this study was heightened by the discovery^ that diphenylchlorophosphine undergoes ammonolysis and chloramination producing diphenylphosphonitrilic trimer and a phosphonitrilic precursor,^ '^' [(CgHc)2P(NH2)-N=P(NH2)(CgHc)2]Cl. On the basis of this discovery a general reaction sequence was postulated in which it was proposed that the chlorophosphine is ammonolyzed with excess ammonia, R2PCI + 2 NH, R2PNH2 + NH^Cl, the aminophosphine reacts with chloramine to yield the diaminophosphonium chloride, R2PNH2 + NH2CI [R2P(NH2)2]C1, and the diaminophosphonium salt undergoes condensation giving the observed products,

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2[R2P(NH2)23C1 [R2P(NH2)-N=P(NH2)R2]C1 + NH^Cl [R2P(NH2)23C1 -»[R2P(NH2)-N=P(NH2)R2]C1 [R2PN], + 2 NH^Cl . Further evidence for this reaction sequence was found in the study of the ammonolysis and chloramination of dialkylchlorophosphines. ^'^'^ With dialkylchlorophosphines the chloramine-ammonia reaction produced dialkyldiaminophosphonium salts in which the alkyl group was methyl, ethyl or n-butyl. In addition, the salt, [(C2Hc)2P(^2^~^^-^^^2^^^2^5^2^^-^' and the trimer, [(n-C^Hq)2PN],^ ^ were produced. It was postulated that these phosphonium salts should undergo self-condensation reactions eliminating ammonium chloride and forming phosphonitrilic derivatives. In addition, it was predicted that interesting phosphonitrilic derivatives should result from the reactions of these salts with PClc, RPCl^, or RoPCl^, where R can be either an alkyl or an aryl group. It was hoped that a study of these processes would not only reveal a method by which cyclic derivatives could be synthesized, but would also lead to high-molecular-weight phosphonitrilic polymers. Although it had been shown that diaminophosphonium salts can be synthesized by chloramination and ammonolysis of di alkyl chl or ophosphines, it was thought that these salts

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might also result from the chloramination of substituted diphosphines. An extension of this method to polyphosphines, (RP) , might also result in the synthesis of triaminophosphonium chlorides. Therefore, the purpose of this study was (1) to investigate the chloramination-ammonolysis of substituted diphosphines and tetraphenylcyclotetraphosphine; (2) to investigate the self-condensation reactions of diaminoand triamino-phosphonium salts and [(C2Hc)2P(NH2^"^^-^^^2^^^2^5^2-'^-^' ^^ ^^^ *° investigate the condensation reactions of some diaminophosphonium salts with PClc, CH^PCl^, and (CH,)2PC1,.

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CHAPTER II HISTORICAL BACKGROUND Phosphonitrilic Derivatives The first phosphonitrilic derivatives to be synthesized were the phosphonitrilic chlorides, [ClpPN] , formed by the reaction of PClc and ammonia. This reaction was (7) noted by Liebig in 185^. Although Liebig did not correctly deduce the empirical formula of the product of this reaction, it was not long before other workers^ ^ confirmed the formula [Cl^PN] . The most significant early study in this field was carried out by Stokes who published a series of papers^ '^ dealing with the reaction of PCl^ with NH^Cl. He confirmed the formation of T-Ji^Gl^ and P^N^CIq, obtained the first reliable physical data on these compounds, and studied their ammonolytic and hydrolytic reactions. Stokes perfected the method of forming these derivatives and discovered higher members of the homologous series, [ClpPN] , from n=5 to n=7. It was Stokes who originated the name "phosphonitrilic" polymer and who first postulated, for the lower members, cyclic structures with alternating phosphorus and nitrogen atoms. He also isolated a highly polymeric phosphonitrilic "rubber," a discovery

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whictL has contributed to the renewed interest in phosphonitrilic derivatives in recent years. Since the discovery of the phosphonitrilic chlorides, a large number of derivatives have been synthesized in which the substituents on the phosphorus atoms vary widely. These substituents can be halogens, pseudohalogens, alkyl-, perfluoroalkyl-, aryl-, aryloxy-, and alkoxy-groups , N-substituted primary and secondary amines, OH and several others. The phosphonitrilic structure, first suggested by Stokes, has been investigated and confirmed by infrared and ultraviolet spectroscopy, nuclear magnetic and quadrupole resonance studies, and electron and X-ray diffraction. References to these works are listed in the •-. ^-, 4-V %. • 4(10,11,12) ™,^ various reviews available on this subject,^ ' ' ' The phosphonitrilic derivatives are now known to contain a backbone of alternate phosphorus and nitrogen atoms in which all of the P-N bonds are of equal length. The trimer, the first member of the homologous series, has a planar, six-membered cyclic structure CI 01 01 \^/ ^; /^ .01 < > 01 01.^. .. .. .^/Cl X„/%i 01-X.X^ci

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The tetramer and h.igher members of the (RpPN) series (R=C1,F) through n=17 are also cyclic. ^^-^ They are not planar but have puckered configurations which give improved overlap of d-orbitals on phosphorus with the lone-pair orbitals on nitrogen providing increased delocalization of the lone-pairs and hence, greater stability. In a number of derivatives for which measurements have been made, the o average length of the P-N bond is 1.56 A. This bond length depends on the group attached to phosphorus and on the size of the ring since it is affected by delocalization of the unshared pair on nitrogen. The N-P-N bond angles are all about 120", however, the P-N-P angle varies from 120° to 150** depending on the ring size and the substituents on 51 phosphorus. The P magnetic resonance spectra of the cyclic derivatives in which the phosphorus atoms have the same substituents have a single peak indicating that the equivalence of the phosphorus atoms is independent of ring conformation. The bonding in phosphonitrilic derivatives is quite interesting and a number of structural features can be rationalized in terms of the bonding theories which have been proposed. X-ray studies have shown that the phosphorus atom is in aji almost tetrahedral environment in the derivatives studied. Thus its single bonds may be considered to be formed using principally sp-^ hybrid orbitals. In the

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trimer the P-IT-P angle is nearly 120° and the nitrogen atom is in a trigonal environment. The sigma-bonding electron 2 pairs and the lone-pair occupy approximate sp hybrid orbitals. The fourth nitrogen electron pair occupies a £orbital and can contribute to pi-bonding with phosphorus. The pi-bonding in phosphonitrilics has excited a lively controversy in the recent literature.^ ' ' The structures shown above imply a resonance of the double bonds and a bonding picture which is similstr to that employed for benzene. However, this analogy is complicated by the necessity of using phosphorus d-orbitals in forming pibonds. The d-orbitals are arranged in space in such a way that considerable overlap with the nitrogen £-orbital, the sp -hybridized lone-pair orbital and with ligand orbitals occurs. Several theoretical descriptions have been proposed for this type of system. Craig'^''" -^ has stated that because of the low local symmetry of the phosphorus atom in phosphonitrilics, the dorbitals are completely non-degenerate. Four d-orbitals, d , d , d , d 2 2, contribute to the overall pi-bonding xy* xz* yz' X -y ' (the d 2-orbital can be involved in exocyclic pi-bonding but ^ z this is not considered to be of importance), and the contributions need not be equal. For pi-bonding, Craig considers the overlap of phosphorus d -orbitals with nitrogen p -orbitals, shown in

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8 Figure 1. The results of his molecular orbital calculations show that, unlike benzene, the highest energy bonding orbital is non-degenerate, as shown in Figure 2. This leads to am aromatic system of delocalized electrons which is distinctly different from that encountered in carbon compounds which utilize only ^-orbital overlap. Any even number of pi-electrons gives a closed shell. Huckel's ^n + 2 rule does not hold. This theory predicts that the delocalization energy per electron increases steadily to a limiting value as the number of pi electrons increases with increasing ring size. Thus the trend in average P-N bond energy (Table 1) is cited as a confirmation of this theory. TABLE 1^^^) AVERAGE P-N BOND ENERGY IN (PNClo) n in (PNCl2)j, 111^1 E(p-N)^-E(P-N)^ (Kcal) 0.39 0.'^^0.60 0.62 Dewar,^ -^ on the other hand, takes advantage of the favorable symmetry properties of the d^^ orbital on phosphorus as well as the favorable overlap properties of the d orbital. Thus he has hybridized these orbital s to form two new pi-orbitals: d^^^ = (d^^ + d^^;) and Figure 5 shows a N-P-N segment of the phosphonitrile structure and illustrates the approximate geometry of the

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d p Fig. 1. -Overlap of N Orbitals with P, Orbital, ^ xz

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E 10 11. JLL _1L -IL 1 I _li_ JU^ -IL J_L C^Hg (PNCl2)3 (PNCl2)^ Pig. 2. -Pi-El ectrpn Energy Levels of CgH^, (PNCl2)j and 2^i\.

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\*^^

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12 relatively simple molecular orbital calculations indicate that th.e delocalization energy is on the order of 0,82 n0 where P is the resonance integral and n is the number of P-N units. This is considered a high value and therefore the theory predicts high stability for the phosphonitrilic structure. Unlike Craig's theory, this approach indicates that the properties which depend on the pi-system alone should not change with increasing ring size. Certain spectral measurements are cited in support of this CIS") approach.^ ^ Superimposed on the sigmaand pi-bonding in phosphonitriles is a third bonding system referred to as the pi'system. This system arises from the overlap of the d 2 2 X — y and d -orbital s of phosphorus with nitrogen lone-pair xy orbitals. As mentioned above, the unshared pair of electrons on nitrogen occupies an s-p hybridized orbital. In the trimeric molecules where the P-N-P bond angle is about 2 120** this orbital is an sp hybrid. However, in the tetramer and larger derivatives the bond angle becomes greater, the lone-pair orbital obtains more p-character, and greater overlap with phosphorus d-orbitals can occur. Electron density can therefore increase on phosphorus at the expense of nitrogen in this second delocalized system. In rationalizing the chemical and physical properties of phosphonitrile derivatives it is difficult to separate

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13 the several effects arising from interactions of the three bonding systems and the inductive effects of the suhstituents on phosphorus. An example of this is presented hy Feakins et al . , ^ ^^ in a thorough study of the basicity of phosphonitrilic derivatives. The observed trend in base strength as the ligands on phosphorus were changed, or as trimers and tetramers were compared, could not be explained by either pi-bonding theory alone. The data could be rationalized, however, by considering the various effects mentioned above, and the conclusion was reached that the base strengths depend in a complex way on a number of parameters. (20) It has been established that the base strength of phosphonitrilic derivatives is dependent upon the availability of nitrogen lone-pair electrons in the ring and that protonation occurs on the ring. Thus, delocalization of the nitrogen lone-pair into the region of the P-N bond has the effect of decreasing the base strength and increasing the P-N bond strength. Both of these effects are sensitive to small changes in the ability of the substituent on phosphorus to accept electrons and can therefore be roughly correlated with the electronegativity of the substituent. Table 2 shows the increase in base strength of certain derivatives with a decrease in the electronegativity of the ligand.

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TABLE 2 1^ (19) BASE STRENGTH OF PHOSPHONITRILIC DERIVATIVES TOWARD PROTONS IN NITROBENZENE AND WATER R CI 0C2H^ C^H^ C2H^ NHC2HC N(G2Hc)2 pKg^ (NPR2)5 <-6.0 -0.2 I.5 6. A8.2 8.5 pK^ (NPR2)^ <-6.0 0.6 2.2 7.6 8.1 8.3 5.9 8.7 (water) (water) 6.5 8.7 (water) (water) In the infrared spectra of phosphonitrilic derivatives there occurs a strong band in the region of 1100-1^00 cm" (see Table 5) which is attributed to P— N ring stretching. The position of this peak is quite variable and the variation can be correlated with the electronegativity of the group attached to phosphorus. If the group has a high electronegativity the nitrogen lone-pair electrons can be delocalized into the region of the P-N bond, strengthening that bond and increasing the frequency at which the infrared peak occurs. Conversely, if the group has a low electronegativity or is an electron releasing group such as an amine, the nitrogen lone-pair is localized on the nitrogen atom and the P— N stretching frequency occurs at lower energy. This effect is illustrated in Table 5.

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15 TABLE 5 VARIATION OF P-N STRETCHING FREQUENCY WITH ELECTRONEGATIVITY OF EXOCYCLIC GROUPS Group Electronegativity (a) P-N Stretching Frequency, Cm"-'Ref.

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16 strengths or the expected P-N stretching frequency. In addition, the electron releasing or accepting abilities of the groups on phosphorus will not affect the pi '-electrons alone but will also affect the sigmaand pi-electrons to some extent. This brief discussion indicates the advancements which have been made since Stokes' pioneering work in understanding the structure and bonding in phosphonitrilic derivatives. Clearly, more experimental data are necessary for a complete evaluation of the bonding theories. Since the work of Stokes, a wide variety of phosphonitrile derivatives have been synthesized, A large number of derivatives may be synthesized because of the wide variety possible in the nature of the groups attached to the phosphorus atom. In addition, the groups on phosphorus in a given molecule can be different from each other. In the cyclic trimer, for example, the groups on neighboring phosphorus atoms can differ. The methods of synthesis of phosphonitrilic derivatives can be considered in two general classes: synthesis from non-phosphonitrilic starting materials, and substitution of the desired group on a previously synthesized P— N backbone. An example of the first method is the synthesis of the phosphonitrilic bromides from PBrc and NH^Br, This method is analogous to Stokes' synthesis of the phosphonitrilic chlorides and gives the trimer and

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17 ( PR PQ ^ tetramer in about 50 per cent yield. ^ * "^ If one uses mixtures of PClc and NH^Br or NH.Cl + PClc -* [NPCl^], /, „ + HCl NH^Br + PBr^ {."S^^v^^ ^ + HBr or PBr^ + Br2 + NH^Br CNPBr2]2 ^ + HBr PBr,and NH^Cl th.e products are mixed chlorobromides such as P^NjCl^Br, P^N5Cl^Br2 and PjNjCl2Br^/50) Most syntheses of new phosphonitrilic derivatives have involved the substitution of different groups on previously synthesized phosphonitrilic backbones. The usual starting material for such a synthesis is the phosphonitrilic chloride trimer or tetramer. Thus, the fluorides can be synthesized by reaction of the chlorine derivatives with fluorinating agents. A number of examples of substitution reactions of this type are presented in Table ^. This method is suitable for the synthesis of a large number of phosphonitrilic derivatives^ ^ although it has not been found to be generally useful for the synthesis of alkyl or perfluoroalkyl phosphonitriles. Only one example of the substitution of such a group is known (h,Oj\ in the chemistry of cyclic phosphonitriles,^ ^^ P^N^Cl^[N(CHj)2]5 + GHjMgBr PjNj(GHj)^[N(CHj)2]3 .

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18 w § — 1 OJ o n isi H 03 W CQ CO "1 > H EH «! > O M o g 8 0) o c -P O o P4 P d CO CD bOrH •H -rH •P fH ^^ O d I II d hO\ CM F^ Ph r
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19 -p o o
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20 The above discussion refers only to cyclic pbospiionitriles and their reactions, A renewal of interest in macromolecular phosphonitriles has occurred in recent years because of the possibility of finding products for military and space industry use. As mentioned earlier, Stokes discovered the first highly poljnaeric phosphonitrilic "rubber" in 1897. Stokes found that by pyrolyzing the cyclic phosphonitrilic chlorides at about 300° C a rubbery material was formed which could be formulated as [PNClp] where n is a large number. This material is thermally stable up to about 350° C where it begins to depolymerize yielding cyclic derivatives. In certain cases ^ * ^ polymeric species of the type, (PNGI2) 'PClc, or HCPNClp) CI, were formed directly from the reaction of PGlc with NH^Gl, It has been postulated^-^ ^ that the first product of this reaction is ammonium hexachlorophosphate NH^Cl + PClc NH^PGlg , This salt could undergo a series of condensation reactions eliminating HCl NH^PGlg H2N-PG1^ + 2 HGl , H2N-PG1^ HN=PG1, + HGl . The new species, HN=PC1t, has two possible courses available for further reaction. It can undergo intermolecular

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21 condensation nHN=PCl^ H=i=NPCl2-^Cl + n-1 HCl . Or it can react with more PCljto form tlie polymer, „. CI CI CI CI I \ / ^p-f-N:=P }-Cl . ^^ Cl Polymers in both these series are oils with n usually having values of from 10 to 20. f 52") Strong evidence^ ^ provided by conductance and capacitamce (dielectric constant) measurements and by electron paramagnetic resonance studies, indicates that the thermal polymerization of the cyclic phosphonitrilic chlorides takes place by ionization of a chlorine atom followed by an electrophilic attack by the positive phosphonium ion 01 Cl Cl Cl > / V/ N' © .Cl + Cl©

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22 > CI Gl \ / IT" N CI I II CI cr %. ^ \ci /Ci ci^^ci [PNcip], . ci ^ij-^ ^N=p— N=p— n=p:: ci" ^ ^^^ > Cl" "^Cl © Cl^^^Cl Cl^l II /CI The other known halogen or pseudohalogen substituted phosphonitriles undergo a similar polymerization at high temperatures. The cyclic fluorides can be polymerized to rubbery materials by heating to 550° C, '^ The trimeric and tetrameric bromides give an elastomer when heated to 250-500° c. ^28,29} Likewise, the cyclic isothiocyanates polymerize when heated to 150° C.^^ ^^ "^ The average molecular weight of the polymeric chloride formed by thermal polymerization has been estimated to be as high as 500,000.

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25 Although these halogen and pseudohalogen substituted phosphonitrilic high polymers are thermally stable, they all share the same disadvantage of being susceptible to hydrolysis. Thus, upon exposure to moisture, HX is evolved with the subsequent loss of rheologically interesting properties. When the high polymers are heated considerably above the temperature of formation, a depolymerization reaction occurs and the cyclic derivatives are regenerated. One observes, therefore, the operation of a dynamic equilibrium, n(Unit)^ V "^ (Unit)„ ^ „ ^ '^m n X m cyclic linear in which the products, or the average molecular weight of the system will depend on concentration, pressure and temperature. Depolymerization is favored thermodynamically at higher temperatures since, in the expression, AF = AH-TAS , the enthalpy is constant because the number of bonds in many small molecules is approximately the same as the number of bonds in a few large molecules made of the same amount of material, and the entropy of many small molecules is greater than the entropy of a few large molecules of the same amount of material. ^^ '' Thermal polymerization has not been observed with the cyclic phosphonitriles which have groups other than

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2^ halogens or pseudohalogens on the phosphorus atoms. However, linear polymers with alkyl groups, aryl groups or Nsuhstituted amines on phosphorus have recently been synthesized hy several new procedures. It has been shown, for example, that lithium azide and sodium azide react viith halophosphines to produce intermediates which undergo thermal polymerization giving high-molecular-weight phosphonitriles. ^•^-^''^ ^ The following reactions are illustrative PBr^ + NaN^ [3r2PN]j^ + N2 + NaBr 195-200* elastomer (C^Hc)PCl2 + NalT^ 170-175° ^ [C^HcClPN]^ + N2 + NaCl average molecular weight >5000 (CF3)2PC1 + LiN^ ^ {0^^)^m^ 37"^°Hg^ C(CF3)2PN]^ .• N2 M.P. 90-9^° C (57) Diphenylphosphinyl azide undergoes a similar reaction. '^ (CgH^)2P(0)N5 + (CgH5)2PCl (C^H5)2P—^N=P(CgH^) 2-3^01 n = 5,^ Furthermore, recently published results ^'^ ^ indicate that the pyrolysis of hydrazinophosphines produces polymeric phosphonitrilic species

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25 n CgH^P[imN(CH^)2]2 ^^^ ^^^° y [CgH^PCN(CH^)2]N]^ 180° + n H2NN(CH^)2 , n P[NHN(CH^)2]3 ^""^ > [P[N(CH^)2] CNHN(CH^)2]N]j^ + n H2NN(CH,)2 . Halophosphines have "been shown to undergo reaction with tetrasulfur tetranitride, S^N^, giving phosphonitrilic ^ A (59,60,61) polymers and precursors:^ ' ' ' PCI J + S^N^ PNCl © PCl^®-^[PNCl2]5 CgH5PGl2 + S^N,, (CgH5PNCl)^-CgH^PCl^ (CgH^)2pCl + S^N^ [(CgH5)2PN]^-(CgH5)2PCl5 The only alkyl-suhstituted high polymer reported in the literature to date was synthesized by methylating polymeric phosphonitrilic chloride^ ^ "by slurrying the chloride with a solution of methylmagnesium bromide or methyllithium. A complete characterization of the products of this reaction has not yet appeared in the literature. With the recent increase in interest in phosphonitrilic chemistry has come the development of several new methods of synthesizing these derivatives from nonphosphonitrilic starting materials. Some of these methods involve the ammonolysis of chlorophosphoranes and are quite similar to the original preparation using ammonium chloride or ammonia and PClc

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26 CgH^PCl^ + NH^Cl [(CgH^)PIICl]j ^ + HClf^^-* (CgK^)2PCl^ + I'TKj(KH^Cl) 1^ (C5H^)2PN] ^ ^^ + NH^Cl (HCl) ^^"^^ (CH,)2PC1, + NK^Cl [(CK^)2?N]^ + HCl ^^C^5^2^^^x (^f^)^l, ^ [(CH3)2PN]5^^^26) (C2H^)2pCl3 + m^ [(C2H^)2PN]^ + NH^Cl [(C2H5)2PN]^ ^^^-^^^°y l
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27 Perfluoromethyland perfluoropropyl -derivatives have been synthesized by the chlorination of bis(perfluoromethyl)aminophosphine and bis (perfluoropropyl )aminophosphine. ' This reaction is carried out at -50° C and it is postulated that the intermediate, [RpP(NH2)Cl]Cl, is first formed. Trimethyl amine is added to the reaction mixture at the completion of the chlorination R2PNH2 + CI2— >[R2P(^2^^-'--'^-^ [R2P(^^2''^^^^-'^ (CH^)jN-^[R2PN]3 z^ ^ + (CH^)jN-HCl . This type of reaction is apparently quite general because it has been demonstrated by Sisler and coworkers^ * that diphenylchlorophosphine produces phosphonitrilic derivatives and precursors when reacted with gaseous mixtures of anhydrous chloramine and ammonia, '^ with H2NNH,C1 and H-,NNH,Clo» and with solutions of anhydrous, ammonia-free chloramine. As pointed out on page 2, the reactive intermediate postulated in the reaction sequence leading to phosphonitriles was the phosphonium ion, [(Cg^Ht-)2P(NH2)2^ when excess ammonia was used, or, [(C^H(-)2P(NH2)C1]^ , when ammonia-free solutions of chloramine were used. These ions could undergo intermolecular condensation producing the precursors which were isolated 2[(CgH^)2P(NH2)2]®— >[(C^H^)2P(NH2)-N=P(NH2)(CgH^)2]® NH®,

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28 H + HCl . Indeed, the ctiloraminatioii-ammonolysis of dialkylchloroptiosphines^-^' ' seems to follow a similar sequence and dialkyldiaminopiiosplionium chlorides were isolated from the reaction mixtures. The Chloramination Reaction Chloramine, NH2CI , was first prepared and used as a synthetic reagent hy Raschig^ -^^ in 1907. Raschig's method consists of the addition of ammonia to dilute, aqueous solutions of hypochlorite ion. Although this method has the disadvantage that only dilute solutions of chloramine can be obtained, and despite the difficulty in preparing the completely anhydrous reagent, this process has been widely used for many years for the commercial production of hydrazine from chloramine and ammonia. In 1951 » Mattair and Sisler^ ^ found that anhydrous, gaseous chloramine could be produced in excellent yields from the gas phase reaction of ammonia and chlorine using an excess of NHt# The first synthetic application of this method was the production of anhydrous hydrazine ^2^^g) -^ ^5 U) ^ ^2^2(jJ) ^ ^^C\s) Subsequently, chloramine was used to synthesize substituted

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29 (71) hydrazines from primary and secondary amines, '^ 1,1,1C72) trisubstituted iiydrazinium salts from tertiary amines,^ (75) and aminophosphonium salts from tertiary phosphmes. ' These reactions may be generalized as follows 2 21^2 + 1^201 -* HNH-im2 + [RNH,]C1 , 2 ^^im + NH2CI R2N-NH2 + [R2NH2^^^ ' R^N: + NH2CI [R^N-NH2]C1 , R^P: + NK2CI r [R3P-ITH23C1 . Hart^'^ ''^^'^ examined thoroughly the chloramination of aminophosphines and showed that chloramine attacks the phosphorus atom instead of the nitrogen atom attached to phosphorus, forming aminophosphonium salts instead of hydra zinium salts R2N-P(Cg^Hn)2 + NH2CI ^ [R2N-P(CgH^)2NH2^^-'» (R2N)2P(CgH^) + NH2CI -* [CR2N)2PCNH2)(CgH^)]Cl , (R2N)^P + im2Cl [(R2N)^PNH2]C1 . A similar study was undertaken by Clemens^ '^ ^ using certain aminophosphines and bis(phosphino)amines. The results were analogous to those of Hart. With the bis(phosphino) amines the reaction was postulated to follow the general course,

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30 RN PRo / 2 \ NH2CI -^ RU PR. NHo PRo RN I <^ PR^ / 2 \ CI \ PR. NH II PR. CI + NH: ^ RN / \ + NH2CI ^ PR. PR. WE II RIT + NH^Cl PR2 NH II PR. RN / \ PRo I 2 CI . Tlie ctiloramination-ammonolysis of monochlorophosphines lias been neationed previously (pages 2, 28). Since halopliosphines can be synthesized by cleavage of diphosphines and polypbosphines with halogens, ' * "^ it seems reasonable to expect chloramine to cleave the P-P bond in a similar manner. However, alkylation of diphosphines with alkyl halides, which is formally analogous to the chloramine reaction, ^'^'^ produces different results with different diphosphines. For example, tetramethyl-, tetraethyl-, and tetra-n-butyldiphosphine react with methyl and ethyl iodide to form diphosphonium salts

PAGE 39

31 R2P-PR2 + H'l [H2P-PH2R*]l/'^'^'®°^ R = CPI^, C2H^, n-C^Hg R = CH7, C^H[On the other hand, tetra-cyclohexyldiphosphine is cleaved by methyl iodide as is tetraphenyldiphosphine (CgH^^)2p-P(CgH^^)2 + CH3I [(CgH^l)2PCCH3)2]I [(CgH3_^)2P(CH3)I]I^'^'^^ (CgH^)2P-P(CgH^)2 + 3 CH3I [(Cg^H^)2P(CH3)2]I + [(CgH^)2P(CH3)I]I /81,82) Burg^ -^^ compares the R2P-sroup with a halogen or pseudohalogen and states that diphosphines undergo many reactions in a manner v;hich is characteristic of halogens. If one applies this idea to the chloramine reaction, one would predict that phosphorus-phosphorus "bonds would undergo cleavage with chloramine.

PAGE 40

CHAPTER III REACTION OF THE CHLORAMINE-AMMONIA MIXTURE WITH SUBSTITUTED DIPHOSPHIRES AND TETRAPHENYLCYCLOTETRAPHOSPHINE Experimental Manipulation of materials , -The diphosphines used in this study are extremely sensitive to oxygen, and detailed precautions were taken to prevent contamination by oxygen from the air. Similarly, some of the products formed in this study are sensitive to moisture, and precautions were taken to avoid contamination of solvents and other reagents by moisture. Benzene was either obtained as the reagent grade product and stored over calcium hydride or obtained as the technical grade product and distilled and stored over calcium hydride. Petroleum ether and diethyl ether were obtained as reagent grade products and were stored over calcium hydride. Other solvents used were reagent grade. Tri-n-butylphosphine was obtained from Food Machinery and Chemical Corporation and used as obtained. Phenyldichlorophosphine and diphenylchlorophosphine were obtained from Victor Chemical Works and used as obtained. These reagents were transferred by pipette under a stream of dry 52

PAGE 41

35 nitrogen. Teorametliyldipiiospliine and tetraethyldiphosphine are liquids at room temperature and were purified "by distillation at reduced pressure. They were stored and transferred by pipette under nitrogen in a D. L, Herring Model HE-^5 Dri Lab equipped v/ith a Model HS-93 Dri Train. Tetrapbenyldiphospbine and tetrapbenylcyclotetrapbospbine are solids and were stored and transferred under nitrogen in the dry box. Infrared spectra . -Infrared spectra of the compounds produced in this study were determined using a Perkin-Elmer Model 337 grating infrared spectrometer. A summary of the spectral bands of these compounds between 2.5 and 25 microns is presented in Table 5. Solid samples were examined between KBr disks as Nujol mulls, or, when the solid melted below lOCC, as a melt. In certain instances thin films could be obtained by carefully evaporating a chloroform solution of the sample on a KBr disk. Samples of substances which are sensitive to moist air were prepared for infrared analysis in the dry box. Elemental analyses . -Elemental analyses and molecular weight determinations were performed by Galbraith Laboratories, Inc., Knoxville, Tennessee. Several nitrogen analyses were carried out in these laboratories using a Coleman Model 29 Nitrogen Analyzer.

PAGE 42

5^ TABLE 5^^'' INFRARED ABSORPTION DATA (Cm"-'-) [(CHj)2P(NH2)2]Cl, Nujol Hull^^^ 3920(w), 3850(w), $260(vs,b), 29^0(vs), 2850(vs), 2620(ei), 2560(w,sti), 2530(w,sli), 2^00(m), 2260(v;O, 2200(w), 2160(w,b), 2100(w,sii), 2060(w) , 2000(w), 19^0(in), 1625(w), 1570(s), 1^60(s), 1^20(s), 1^10(iii,sli) , 1375(ni), 1310(m), 1300(s), 1070(sh), lO^O(s), 990(s), 951(s), 885(m), 860(iii), 835(ni), 762(s), 695(s), 600(b), 527(b). [(C2H^)2P(NH2)2]C1, Nujol Hull^^^ 39^0(w), 3160(vs), 3060(vs), 29^0(vs,b), 2850(vs) , 26^0(w), 2550(w), 2330(w,sh), 2150(w), 2060(w), 1960(w,sli), 1920(w), 1870(w,sb), 1755(w,b), 1665(w,b), 1560(s), 1^60(vs), 1395(s), 1380(s), 1275(s), 12^0(m), 1160(w,b), 1075(s,sh), 1050(s), 1019(s), 980(s,sh), 9&8(s), 910(s), 761(s), 733(s), 721(s), 665(s), 625(s,b), 500(w,b), ^^7(21). (G^H^)2PC0)NH2, Nujol Mull 32^0(s,b), 3125(s), 29^0(vs), 28&0(vs), 1970(w), 1900(v;), 1820(w), 1779(w), 1680(w) , 1595(m) , 1560(s), 1^85(111), 1^60(vs,b), 1^^0(vs,s}i), 1^39(vs), 1^20(w,sh), 1380(s), 1365(m,sh), 15^0(w) , 1510(m), 1275(w), 1260(w), 1175(s), lllO(s), 1105(s), lOoO(in), lOlO(w), 990(m), 910(s), 858(w), 8^9(w), 752(s), 720(s), 695(s), 620(w), 532(s), 518(s), ^88(m), 439(w). [(GgH^)2?(NH2)2]Cl, Nujol Mull 5170(s), 3073(s), 2980(vs,sli), 29^0(vs), 2860(vs), 2710(w), 25^0(w,b), 24^0(w), 1970(w), 1900(w), 1815(w), 1780fw), 1665(w,b), 1595(m), 1560(s), 1485(ni), 1^60(s), l^^O(s), 1410(m), 1380(s), 1365(m,sb), 13^0(w), 1320(w), 1280(w), 1190(w), 1160(w), lllO(s), 1075(w,s]i), 1025(s,sb). lOlO(s), 990(s,sli), 980(s), 922(m), 910(m), 855(w), 8^0(w) , 756(s,sh), 751(s), 7^2(s), 720(s), 691(s), 638(w,b), 620(w), 5^9(w,b), 510(s), 505(s,sh), ^72(m), 43^(w), ^13(m).

PAGE 43

35 Table 5 (cont'd) Suspected Cl-£ p=:NH^ P=NH, Kelt 3^00(s,sh), 3210(vs), 3050(vs), 2950(s), 29^0(sli), 2635(w), 2600(w), 2300(31), 2250(w), 1960(m), 1900(111), 1820(iii), 1770(w), 1720(vO, l&70(iii), 1640(ia), 1590(s), 1550(vs), 1480(s), l^^O(vs), 1280(s,sli), 1205(vs,vb), 1115(s), 1015(iii), 910(iii,b), 799(111), 7^2(s), 692(s), 685(sli), 615(w) , 502(s,vb). [(CgK^)P(NH2)^]Cl, Nujol Mull 3375(ni)j 3250(s,s]i), 3170(s), 3075(s), 29^0(s,sli), 2900(vs), 2850(s), 1590(w) , 1559(m), 1^50(s), l^^O(s), 1^15(m), 1380(s), 1135(s), 108^(w), 1070(w), 1025(w), 985(m), 925(---,sh) , 875(m), 798(w), 763(s), 721(w), 705(w) , 692(m), 620(w,b), 510(in), 47^(m). (CgH^?(0)(lTH2)2» Nujol Mull 5350(s), 5275(s,sli), 5220(s), 3110(s,sh), 3055(ni), 29^0(vs), 2850(vs), 27^0(w), 1955(w) , 1900(w), 1770(w), 1590(m), 1560(m), 1^60(s), l^^O(s), 1410(m,b), 1380(s), 1330(w), 1310(w), 1182(iii), 1155(vs), 1118(s), 10&0(iii), lOlO(m), 939(s), 915(m,sh), 885(m), 855(w), 7^5(s,sb), 7^0(s), 720(iii), 69^(s), 620(w), 568(w,b), 520(s), 512(s), ^9^(w) , 435(w,b). (a.') ^ -^s, strong; m, medium; w,weak; b, broad; v,very; sh, shoulder.

PAGE 44

56 Melting points v;ere determined in a Thomas-Hoover capillary melting point apparatus and are uncorrected. Preparation of substituted diphosphines and tetraph.enylcyclot5trar)hosphine ,-Tetramethyldiphosphine and tetraethyldinhosphine were prepared by the desulfuration of the corresponding diphosphine disulfide with tri-n-butylphosphine.^ ' The diphosphine disulfides were synthesized by the Grignard method from PSCl^ and R?igBr(S = CH^,, Q>^A . This method has been thoroughly discussed elsewhere. ' ' ^ To the solid diphosphine disulfide under a nitrogen atmosphere was added by pipette, tri-n-butylphosphine according to the stoichiometry of the following general equation R2P(S)-?(S)R2 + 2(C^Hg)jP -^ R2^-PR2 + 2(C^H<^) jP(S) . It was convenient in this study to use from ten to fifteen grams of the diphosphine sulfide in each run and to mix the reagents in a 200 ml round-bottomed distillation flask. The mixture was then heated under reduced pressure. The tetraalkyldiphosphine was obtained by fractional distillation from the reaction mixture. The observed boiling point of tetramethyldiphosphine \
PAGE 45

37 slow because of the difficulty in removing the diphosphines from (C^Hq);,?S in which they are soluble.^ ^ At the completion of the distillation the diphosphines were placed in stoppered receivers under nitrogen and stored in the dry box until needed. The infrared spectra and nuclear magnetic resonance spectra of these tetraalkyldiphosphines have been treated thoroughly elsewhere^ ^ and need not be considered here. Tetraphenyldiphosphine was prepared by the reaction of tri-n-butylphosphine with diphenylchlorophosphine^ ' which can be represented by the following equation (C^H,^)^? + 2(C.H^)2PC1 (C.H^)2P " ^^^^^^2 + (G^H^)jPCl2 . In a typical experiment, 5.15 ml (1^ mmoles) of tributylphosphine was pipetted into 5.0 ml (27 mmoles) of diphenylchlorophosphine in a Minilab reaction flask (Fig. 5) fitted with a stirrer and a nitrogen inlet and outlet. The mixture was stirred until it became homogenous. It was then allowed to stand under a nitrogen athosphere for about three days. At the end of this time the reaction mixture had become a solid, crystalline mass. This crystalline mixture was extracted under a nitrogen flow with cool, freshly boiled, distilled water until the washings gave no chloride test with aqueous silver nitrate. The white, crystalline

PAGE 46

38 Nitrogen Inlet Stirrer Filter Fig. 5.-Minilab Reaction Flask,

PAGE 47

39 residue was dried in vacuusi and transferred to the dry box. M. P. 118-121* C (Lit/^^-^: M. P. 120.5° C). The average yield of tetraphenyldiphosphine produced by this method of synthesis was about ^0 per cent of theory based on the amount; of diphenylchlorophosphine used. Although strict precautions against oxidation of the diphosphine were taken, a small amount of tetraphenyldiphosphine monoxide^ was probably present in each sample. Tetraphenylcyclotetraphosphine was prepared by the reaction of tri-n-butylphosphine with phenyldichlorophosphine^ '^ ^ as indicated by the following equation In a typical experiment, 5.0 ml (55.6 mmoles) of phenyldichlorophosphine was pipetted into 8.2Aml of tri-n-butylphosphine in a Minilab reaction flask (Fig. 5) under nitrogen. Heat was evolved and after a few moments of stirring the reaction mixture became a solid, crystalline mass. When the mixture had cooled to room temperature, it was extracted with copious amounts of absolute ethanol. This extraction was continued until the acidified washings gave no precipitate with aqueous silver nitrate. The white, crystalline residue was dried in vacuum and transferred to the dry box. M. P. 155-155° C (Lit.^^^^: M. P. 153-155° G). The average yield of tetraphenylcyclotetraphosphine produced

PAGE 48

^0 by this method of synthesis v/as 50 per cent of theory based on the amount of phenyldichlorophosphine used. Strict precautions were taken to avoid oxidation of the product. The infrared spectra of tetraphenyldiphosphine and tetraphenylcyclotetraphosphine are available in the literature.^ ^ Hov;ever, a controversy exists in the current literature concerning the nature of tetraphenylcyclo("89 90") tetraphosphine. ^ -"> -' ^ The material produced in this study has the melting point and infrared spectrum reported for "form A" which is considered to be one stereoisomeric form of (C^H^P)^. Preparation of chloramine .^ -The preparation of gaseous chloramine was carried out in a generator shown diagrammatically in Figure 5.^ ^ Anhydrous ammonia, chlorine and nitrogen v;ere metered in rotameters and mixed in a glass reaction tube. The approximate rate of introduction of the gases was: Clp, 0.1 mole/hr, ; NH^* 1'2 mole/hr. ; Np, 0.5 mole/hr. The approximate production rate of chloramine was 0.1 mole/hr. Since ammonia was present ii a large excess of that required by the stoichiometry of the reaction the effluent gases consisted of chloramine, ammonia and nitrogen. --xass wool plugs were placed in the reaction tube

PAGE 49

^1 •H O O O u •p •H o CO Q) -P 0) +3 o "TV/u o -p CD d o •H a O r-i xi o 0) EH I >^

PAGE 50

42 to filter out the finely divided ammonium chloride produced in the reaction. The effluent gases were bubbled into a receiver containing the solution of the substance to be chloraminated. The Reaction of the Chloramine-Aminonia Mixture v/ith Tetramethyldiphosphine (CH^)2P-P(CH,)2 + 5 NH2CI + 2 NH^ -* 2[(CH,)2P(NH2)23C1 + NH^Cl In a typical experiment, 1.0 ml (7.1 mmoles) of tetramethyldiphosphine was dissolved in 75 ml of dry benzene and exposed to the effluent gases of the chloramine generator. A reaction took place immediately. A white precipitate formed and the reaction mixture grew warm. After IO-I5 minutes of chloramination the reaction appeared to be complete and the temperature of the mixture dropped to about 20" C because of evaporation of the solvent. Chloramination was continued for 5-10 minutes beyond this point to insure exposure of the reaction mixture to an excess of chloramine. At the completion of the chloramination the benzene was removed by filtration. The solids remaining on the filter were extracted with 60 ml of hot, 50/50 ethanol-acetone mixture. White crystals precipitated from the solution as it slowly cooled to room temperature. These crystals were removed by filtration and dried in vacuum. N.P. 191-19^° C.

PAGE 51

^5 Anal. Found: N, 21.^7. Calculated for [(CH,)2P(NH2)2^C1 : N, 21.79* The infrared spectrum of this material was identical with that of dimethyldiaminophosphonium chloride (M.P. 192-19^° C) produced by chloramination-ammonolysis of dimethylchlorophosphine.^ * ^ Addition of petroleum ether to the mother liquor caused a larger portion of dimethyldiaminophosphonium chloride to precipitate. Yield: 1.08 g (65% of theory). The Reaction of the Chloramine-Ammonia Mixture with Tetraethyldiphosphine (C2H5)2p-P(C2Kc)2 + $ ^^2^^ + 2 NH^ -* 2[CC2H^)2P(NH2)2lCl + NH^Cl 3(C2H^)2P-P(C2Hc)2 + 9 NH2CI + 6 NH^ -* 2[(C2H^)2PN] ^ + 9 NH^Cl Tetraethyldiphosphine (5 mmoles) was dissolved in 75 ml of dry benzene and exposed to the effluent gases of the chloramine generator. A white precipitate formed immediately and the solution became warm. After 10-15 minutes the temperature of the solution fell to about 20° C because of evaporation of the solvent, and the reaction appeared to be complete. Chloramination was continued, however, for 5-10 minutes longer until a relatively large excess of chloramine and ammonia had been added to the reaction mixture. The benzene solution was removed from the

PAGE 52

precipitate by filtration and evaporated to dryness, A trace of oily crystals was observed. The crystalline material was separated from the oil by dissolving it in 50-60° petroleum ether. The oil was discarded. Evaporation of the petroleum ether yielded crystals which melted at 113-115° C and which sublimed readily at 50-^0° C and 0.1 mm Kg. This material was identified by its infrared spectrum and melting point (see Chapter IV for a more complete description of the identification of this material) as diethylphosphonitrilic trimer*^^^^ (Lit: M.P. 117-119° C). Yield: trace (1-5 millig. ) . The solids remaining on the filter were extracted with three, 10 ml portions of absolute ethanol. This solution was evaporated to dryness and the resulting crystalline extract was dissolved in 10-15 ml of hot, 50/50 ethanolacetone mixture. This solution was cooled with an ice bath and to it was added approximately 100 ml of 60-110° petroleum ether. The product crystallized from the solution as well formed, white needles. These crystals were filtered and dried in vacuum. M. P. 103-105° C Anal. Found: N, 17.9. Calculated for 1(02^^)2^(^2^^^^'' ^' ^7.89. The infrared spectrum of this material was identical with that of diethyldiaminophosphonium chloride (M. P. 106-108.5° C) produced by the chloramination-ammonolysis of diethylchlorophosphine.^^'^'* Yield: 1.07 o (68% of theory).

PAGE 53

^5 The Reaction of the Chloramine-Ammonia Mixture v;ith Tetraphenyldiphosphine In a typical experiment, 1.05 S (2.8 mmoles) of tetraphenyldiphosphine was dissolved in 50-75 ml of dry benzene and exposed to the effluent gases of the chloramine generator, A v;hite precipitate formed immediately and the reaction mixture grew warm. Chloramination was continued for about 20 minutes to insure exposure of the reactants to an excess of chloramine. At the completion of the reaction the temperature of the reaction mixture had fallen to about 20° C because of evaporation of the solvent. The benzer.a solution was removed from the white precipitate by filtration and the solids were washed with 25 ml of fresh benzene. The combined filtrate and washings were evaporated to dryness yielding 0.39 g of a white powder which melted in the range of 80-110° G. This solid was redissolved in 10 ml of boiling benzene. Upon cooling, white crystals precipitated from the benzene solution and were filtered and dried in vacuum. M. P. 158-160° C. Anal, Found: N, 6.6. Calculated for (C^Hc)2P(0)NH2: N, 6.^8. The infrared spectrum (Fig. 7) is consistent for the formulation, (C^Hc)2?(0)NH2* Evaporation of the benzene solution to dryness yielded an oily foam. More crystalline (C-:Hc)pP(0)NH2 could be recovered from this foam by dissolving it in 2-^ ml of boiling benzene, adding hexane to

PAGE 54

^i

PAGE 55

^7 the h.ot solution until it became cloudy, and allowing this mixture to stand for several hours. By repeating this process several times, all hut a trace of the sample was recrystallized. and shown hy its melting point and infrared spectrum to he (Cg^Hc)2P(0)j^2* '^"^® noncrystalline residue v;as a yellov; oil and was discarded. In other experiments, evaporation of the benzene solution yielded a dark foam which appeared to be air sensitive, turning wet upon exposure. After recovery of the first crop of crystalline (CgHr) 2^(0)^2 from this mixture, further attempts at recrystallization resulted in the formation of oily products. The dark foam produced by evaporation of the benzene solution melted at 35-^0° C. Its infrared spectrum is shown in Figure 8.. Anal. Found: C, 55.5^; H, 6.05; P, 12.67; N, 6.06; Mol. Vt. (cryoscopic in benzene), ^50. The P:N ratio is 1:1. This implies the 6^/65 structural unit, 4— P=N-4, for which the calculated composition is: C, 72.^; H, 5.1; P, 15.6; N, 7.0. The analysis, however, is low and indicates that the material may consist also of oxygen-containing material. The benzene-insoluble solids remaining on the filter were extracted with two, 10 ml portions of hot chloroform. The extracts v;ere combined and concentrated to about half the original volume by evaporation. White crystals precipitated and were removed by filtration and dried in vacuum.

PAGE 56

^8 cu tH

PAGE 57

^^9 N.P. 230-252° C. Anal . Found: N, 8.9. Calculated for [(CgHc)2P(NH2)-N=P(NH2)(C^Hn)2]Cl: N, 9.50. The infrared spectrum of this material was identical with that of [(C^H^)2P(NH2)-N=P(NH2)(C^H^)2]C1 produced by the chloramination-ammonolysis of diphenylchlorophosphine. ^ ' Yields 0.^2 g (55% of theory based on tetraphenyldiphosphine used). If the vacuum drying process was not prolonged, the (2) 1:1 chloroform adduct^ ^ of the substance was obtained. Anal. Found: N, 7.5. Calculated for [(CgHc)2P(NH2)-N=P(NH2)(C^Hn)2]Cl'CHCl,t N, 7.56. The chloroform-insoluble residue was extracted with 50 ml of hot, 50/50 acetone-ethanol mixture. Addition of diethyl ether to this solution caused a small amount of NH^Cl to precipitate. The solution was filtered. Upon addition of a copious amount of diethyl ether more crystalline material precipitated. This material was filtered and dried in vacuum. M.P. 20^-206° C (dec). Anal. Found: C, 56.22; H, 5.8^; P, 11.78; N, 10.69; CI, 1^.50. Calculated for [(G^En) 2^(^)2'^^'^' ^' 57.0^; H, 5.58; P, 12.26; N, 11.09; CI, 1^.05. This analysis indicates that the material may be slightly contaminated with ammonium chloride. The infrared spectrum of this material (Fig. 9) is consistent for the formulation [(C^Hc)2P(NH2)2]01, and shows that the amount of ammonium chloride present is too small to be detected by this infrared technique. Attempts to

PAGE 58

50

PAGE 59

51 syntliesize the hexafluorophosphate and tetraphenylborate derivatives of trie diphenyldiaminoph.osp'hoiiiuiii ion by metathesis in water failed. Yield of diphenyldiaminophosphonium chloride: 0.20 g (1^% of theory based on tetraphenyldiphosphine used) , The remaining insoluble material was shown to be ammonium chloride, The I 'action of the Chi oramineAmmonia Mixture with Tetraphenylcyclotetraphosphi ne In a typical experiment, 0.98 g (2.2? mmoles) of tetraphenylcyclotetraphosphine was dissolved in 50-75 nil of dry benzene and exposed to the effluent gases of the chl oramine generator. A white precipitate formed immediately and the solution grew warm. The reaction was apparently complete when the temperature of the mixture dropped to about 20° C because of evaporation of the solvent. Chloramination was continued for 5-10 minutes longer to insure exposure of the reactants to an excess of chloramine and ammonia. The benzene solution was removed from the precipitate by filtration and the residue was washed with 25 ml of dry benzene. The filtrate and washings were combined and evaporated to dryness yielding 0.-4-0 g of a white, air-sensitive solid. This solid melted to an opaque liquid at 68-72° C and the melt did not become clear when heated to above 200° C. The analytical data for

PAGE 60

52 several samples of this material are summarized in the table below. Found C i E N CI Mol. Vt. Sample 1 51.83 5.95 17.53 15.^^0 2.3 9^0 (in benzene) Sample 2 20.31 17.13 20.^1 17.18(Koeldahl) Sample 3 ^9.7^ 5.21 21.^3 19.20 ^.08 870 (in benzene) The P:N ratio in these samples is 1:2. This implies the C H NH structural unit 6 5.. y 2 , and a likely structure might be 6 5\ / 2 6 5\ / 2 Cl-t P=N-3 P=NH where n » 5 . The calculated elemental analysis for such a formulation is: C, ^9.9^; H, ^.97; P, 21.50; N, 19.^2; 01, ^.16; Mol. Wt. 865. The infrared spectrum (Fig. 10) is consistent for such a structure. Pyrolysis of the crude material at 200° G and 0.10 mm Hg produced ammonium chloride as a sublimate and an intractable residue which had a nitrogen content lower than the original material. The benzene-insoluble precipitate was extracted with 50 ml of 50/50 ethanol-acetone mixture. The solution was removed from the insoluble ammonium chloride by filtration and a product was precipitated by the addition of copious amounts of diethyl ether. Upon filtration and drying in vacuum the crude material was found to melt with decomposition in the range 160-170° C. After recrystallization

PAGE 61

53 o u (D > :5 •H E^ Ph o O P o d o o rH -P
PAGE 62

5^ from 50/50 acetone-etiianol, the observed melting point was 164-165° C. Anal . Found: C, 58.24; H, 6.15; P, 16.37; N, 21.96; CI, 17.35. Calculated for liG^E^)l>{mi^) 2G1: C, 37.61; H, 5.79; P, 16.17; N, 21.93; CI, 18. 50. The infrared spectrum (Fig. 11) is consistent for the formulation [(CgH£-)P(NH2)2301. Attempts to synthesize the hexafluorophosphate and tetraphenylborate derivatives of the phenyltriaminophosphonium ion by metathesis in water failed. Yield: 0.24 g (14% of theory). The phenyl triaminophosphonium chloride so prepared was quite sensitive to hydrolysis. Slow recrystallization of the product from alcohol exposed to the atmosphere produced the hydrolysis product, C^HcP(O) (NH2)2. M.P. 180-181° C (dec.) (Lit.^'^^'': M.P. 189° C). Anal. Found: C, 45.47; H, 5.81; P, 19.86; N, 17.95; (by difference), 10.43. Calculated for CgHcP(O) (1^2)5 '• 0, 46.16; H, 5.81; P, 19.84; N, 17.94; 0, 10.25. The infrared spectrum of phenylphosphinic diamide is shown in Figure 12. Discussion The results of this study show that under the conditions of our experiment chloramine cleaves the phosphorusphosphorus bond in tetramethyldiphosphine, tetraethyldiphosphine, tetraphenyldiphosphine and tetraphenylcyclotetra-

PAGE 63

55 o o d-

PAGE 64

56 a o :5 o CM o o -P o Pi •d 0) u C! H I C\J

PAGE 65

57 ptiosphine. The chloramination-ammonolysis of tetramethyldiphospliine yields dimethyldiaminophosphoniuni chloride as the only important product. Thus, this reaction appears to be quite analogous to the chloramination of dimethylchlorophosphxne. ^^' ^ Similarly, the chloramination-ammonolysis of tetraethyldiphosphine gives diethyldiaminophosphonium chloride in yields v;hich average "betvjeen 60 and 70 per cent of theory. Unlike in the chloramination of diethylchlorophosphine, however, the intermediate, [(C2H^)2P(NH2)-N=P(ITH2) (C2H^)2]C1, is not produced. On the other hand, a trace of diethylphosphonitrilic trimer is observed. It is curious that only a trace of diethyldiaminophosphonium chloride undergoes complete condensation, $[(C2H^)2P(NH2)2-IC1 l(.Z^^)^m^ + 5 NH^Cl , while no intermediate product of condensation, [(C2H^)2P(NH2)-N=P(NH2)(C2Hc)23Cl, is observed. One might speculate that at some time during this exothermic reaction the complete condensation could momentarily become kinetically favored. The chloramination-ammonolysis of tetraphenyldiphosphine is not so straightforward and simple as the chloramination-ammonolysis of tetraalkyldiphosphines. However, it is clear that cleavage of the phosphorus-phosphorus bond occurs. The principal product which could be isolated and

PAGE 66

58 identified v;as the substance, [(CgH^)2p(im2)-N=P(rTH2)(CgH-)2]Cl. This was also an important product of the chloramination-ammonolysis of diphenylchlorophosphine. ^ A more interesting result is the identification of [ (CgHn)2p(NH2)23Cl as a product of the reaction, Diphenyldiaminophosphonium chloride or the diphenyldiaminophosphonium ion is the postulated reactive intermediate^ ^ in the formation of [(CgH^)2P(ira2^~^'=^^^'^2^^^5^5^2^^^ ^^^ [(CgH^)2PN]^ from (CgHc)2pCl, NH2CI and i;^^;,. Unfortunately, the yield of this material was small and it could not be purified from traces of ammonium chloride. The substance is soluble in polar solvents such as alcohol and water but is insoluble in chloroform and non-polar solvents such as benzene and n-hexane. Dissolved in water, it gives an immediate test for chloride ion with Agg). However, it must hydrolyze rapidly in v^ater for no metathetic derivative of PF^ © or (C^Hi-)^B could be detected. A third product which was isolated and identified was the amide of diphenylphosphinic acid, (Cgri-)2P(0)I\Tl2* This material v;as characterized by its melting point, nitrogen analysis and infrared spectrum. It is quite possible that during its preparation, the starting material, tetraphenyldiphosphine, became contaminated v;ith the monoxide, (C^Hc)2P-PC0)(C5Hc)2^^^is material might undergo

PAGE 67

59 chloraLmination-aiiinionolysis giving the amide as one product, NH2CI This is an interesting possibility and should he investigated further. Alternatively, the amide may arise from the hydrolysis of diphenyldiaminophosphonium chloride, [(CgH^)2P(NH2)2]Cl + K2O -* (G^H^)2P(0)NH2 + NH^Cl . Finally, in some experiments an intractable, benzenesoluble tar was isolated from the chloramination-ammonolysis of tetraphenyldiphosphine. This material melted at Just above room temperature and contained no chlorine, but still appeared to be air sensitive, turning wet after a few minutes exposure to the atmosphere. Some structural features are evident from examination of the infrared spectrum (Fig. 8). This spectrum shows N-H stretching and deformation peaks in the region from 5580 cm" to 5I8O cm" and at 1575 cm" , respectively. Phenyl C-H stretching peaks and "C=C" stretching peaks are observed at 50^0 cm" and at 1590 cm"^, 1^80 cm""'and 1^59 cm" . A strong, broad peak is observed at 1260 cm" which is characteristic of "P=N" stretching in phosphonitrilic derivatives. A strong peak occurs at 1175 cm" , a region which is sometimes

PAGE 68

60 associated with, the phosphoryl group, — ? — ^ 0. This peak appears as a shoulder on a strong peak at ll&O cm" which might be attributed to phenyl C-H in-plane bending. A sharp, strong peak occurs at about 111? cm" . This peak is usually observed in compounds in which the phosphorus atom is tetracoordinate and bonded to at least one phenyl f (95) group. >'^J j^-t 921 cm" a peak of medium intensity occurs which might be assigned to the P-KH-P grouping. A similar peak occurs in the spectrum of \.i0^n)2^iW^2^-^-'^(J^B.2)(.0^^)2^^'^'^'^^ Several sharp peaks appear in the region of 800-595 cm" . Peaks in this region are usually attributed to C— H out-of-plane bending vibrations in the phenyl groups and to P-phenyl bonds. The observed molecular weight (450) of this substance is in the right range for the grouping, i{0^^)^-l^-'P {0,^^)2^'* however, the analytical data obtained so far are not helpful in completing the characterization of this substance. The infrared spectra of l{0^n)2^(J^R2^2^^^ ^^^ (C^Hc-)2p(0)KHp (Figs. 7 and 8) resemble each other closely. In fact, in the region from 4000 to 1200 cm" very little difference is noted in the placement and number of peaks in the two spectra. At 1175 cm" , however, the spectrum of (Gr-Ht-)2P(0)NH2 ^^.s a strong absorption which is attributed to the phosphoryl group. This peak is absent in the spectrum of [(CgHi-)2p(NH2)2]Cl. The two spectra also differ

PAGE 69

61 considerably in the region from 1105 "to 695 cm" . This region contains the C— H bending peaks as well as the peaks attributed to P-phenyl bonding. In general, we can saythat the infrared spectra confirm the identity of these compounds. The chloramination-ammonolysis of tetraphenylcyclotetraphosphine produces a material which is apparently a linear phosphonitrilic derivative. An examination of its infrared spectrum (Fig. 10) shows a broad N-H stretching band which peaks at 5210 cm" , a strong N— H deformation band which peaks at 1550 cm" , a very broad band at 12501155 cm" which is very similar to the "P=N' stretching band in phosphonitrilics, and a sharp peak at 1115 cm" which is associated with tetracoordinate phosphorus bonded to phenyl. In addition the infrared spectrum contains peaks usually attributed to phenyl C— H stretching and bending vibrations, "C=C" stretching vibrations and P-phenyl bonds. Thus, the infrared spectrum is consistent for the unit, ^/I'x -1 • The analytical data compiled on several samples of the same material indicate the same unit since, in all cases, the P:N ratio was almost exactly 1:2. The average molecular weight of this material, determined .ryoscopically on several samples, varied from 750 to 950 indicatinan average of 5-7 P-N units. The

PAGE 70

62 complete solubility of this substance in solvents such as benzene and chloroform indicates that the small amount of chlorine present is not caused by impurities such as ammonium chloride. Therefore, v;e postulate that the chlorine is bonded to the phosphorus atom of the molecule, perhaps as an end-stopping group. This postulate is supported somewhat by the broad, infrared peak at 510 cm which is in the region of absorptions attributed to the P-Cl bond. The postulated structure is then, 6^ / 2 6^ / 2 CI— f — -^P=N— 3 P=NH , where the average value of n is 5. n This formulation is supported by infrared and analytical data as well as by consideration of the physical properties of the material. Clearly, hoxvever, the structure of this material is still a subject of speculation. Additional physical and chemical information should be obtained on this interesting substance. At the time of this writing a nuclear magnetic resonance investigation v/as being undertaken. However, the results of such a study are not yet available. The second compound obtained from the chloraminationammonolysis of tetraphenylcyclotetraphosphine was identified as phenyl triaminophosphonium chloride, [(CgK^)P(NH2) j]Cl. Although this material could not be isolated in absolute purity from ammonium chloride, there is little question of

PAGE 71

65 its identity. The infrared spectrum (Fig. 11) contains the usual N— H stretching and deformation peaks and the peaks associated with phenyl C-H bonding, phenyl "C=C" bonding and P-phen^'"l bonding. A strong peak is observed at 1135 cm" which is attributed to tetracoordinate phosphorus bonded to phenyl. The absence of peaks in the region from 1300 cm" to 1150 cm" indicates that the material has neither a condensed P— 1T=P structure, nor is it contaminated with the amide, C^Hc-P(O) (I^IHo)^. The amide was synthesized easily from phenyl triaminophosphonium chloride by exposing a solution of the chloride in alcohol to moist air. Indeed the infrared spectrum of the amide (Fig. 12) is quite similar to that of phenyl triaminophosphonium chloride. However, it contains a sharp peak at 1155 cm" attributed to the phosphoryl group. Although portions of this study are incomplete, there are certain results which are significant. We can now state onat chloramine cleaves the phosphorus-phosphorus bonds in substituted diphosphines and in tetraphenylcyclotetraphosphine. Although other reaction sequences may be possible, we feel that the first step in the chloramination of diphosphines involves the formation of an aminophosphine and a chlorophosphine, R2P-PR2 *" ^^2^^ ~* ^2-^^2 "^ ^2^^^ •

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6^ This step is analogous to the first step in the reaction of certain diphosphines with methyl iodide (Chapter II), and is analogous to the first step in the halogenation of diphosphines. The aminophosphine and the chlorophosphine could then undergo further chloramination and ammonolysis to produce the observed products. This study has provided a convenient new method for the synthesis of dialkyldiaminophosphonium salts. Previously, these derivatives were synthesized from dialkylchlorophosphines v;hich are obtained with some difficulty. For example, instead of using dimethyl chlorophosphine which has a short shelf-life and must be used as soon as it is obtained, we can nov; utilize tetramethyldiphosphine which can be stored indefinitely and used when desired. The convenience of this method for the preparation of dialkyldiaminophosphonium chlorides will be further appreciated in the discussion of Chapter IV which deals with the condensation reactions of these salts. This method seems to favor the formation of diaminophosphonium salts. Thus, using tetramethyldiphosphine and tetraethyldiphosphine ., the corresponding diaminophosphonium salt was either the only product or the major product of the reaction. Chloramination-ammonolysis of diethylchlorophosphine, on the other hand, produces only a 20 per cent yield of the diaminophosphonium salt. Tetraphenyldiphosphine

PAGE 73

65 gives diphenyldiaminopliosphoniuiii chloride, a material which was a postulated product in the chloramination of diphenylchlorophosphine but \<&s never isolated. Likewise, tetraphenylcyclotetraphosphine produces phenyl triaminophosphonium chloride. In view of the possible value of diamineand triaminophosphonium salts as phosphonitrilic precursors (see Chapter IV), we feel that this reaction should be applied to a number of other diphosphines and polyphosphines. This v/ould indicate the generality of the method and possibly make available a variety of diamineand triaminophosphonium salts for further investigation. Some polyphosphines which should be chloraminated are (CF;,P) and (HP) where R is an alkyl group. It would also be interesting to examine the reaction of chloramine with amino-substituted diphosphines such as Cc^Hc-(RpN)?-P(R2^)^f;^t5 and (R2N)2P-P(R2^)2* Summary Chloramination-ammonolysis of tetramethyldiphosphine and tetraethyldiphosphine produces dimethyldiaminophosphonium ch". oride and diethyldiaminophosphonium chloride in good yields, and produces traces of diethylphosphonitrilic trimer. These materials were identified by chemical analysis and by comparison of their infrared spectra and

PAGE 74

66 melting points with those of the authentic materials produced "by oth."-" methods. The chloramination-ammonolysis of tetraphenyldiphosphine produces a new compound, diphenyldiaminophosphonium chloride, and its postulated condensation product, [(CgH^)2P(NH2)-N=P(NH2)(CgH^)2]Cl. In addition, the amide, (CrH|-)p?(0)LTHp, and an unresolved tar were produced in the reaction, Chloramination-ammonolysis of tetraphenylcyclotetraphosphine produces a materi'-l tentatively identified as 6C^ / 2 o^ / 2 01— £ p=N— ] P=NH , where the average value of n is 5. This reaction also produced a new compound, phenyl triaminophosphonium chloride. The identity of this material was established by elemental and infrared analysis and by synthesis of a derivative, C^Ht-P(0)(KH2)2' Infrared data are presented and interpreted in terms of the structures of the compounds synthesized in this study. The chemical evidence leads to the conclusion that the chloramination of diphosphines and polyphosphines causes cleavage of the phosphorus-phosphorus bonds. Further chloramination and ammonolysis of the fragments produces the same materials which arise from the c:iloramination of HPClp or SpPCl coripounds. This reaction constitutes a new

PAGE 75

57 method for the production of diaminoand triaminophosph-onium chlorides. In this connection, the reaction is more convenient than th..' one vmich employs chlorophosphines because diphosphines and polyphosphines are easier to prepare and store.

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CHAPTER IV THE PYROLYTIC CONDSMSATION OF DIALKYLDIAPIIN0PH03PH0NIUM CHLORIDES AITD OF iiG2^n^)2^(^^2^~^~^^^^2^'^^2^^5^2^^-^ Bxperimeatal Manipulation of materials . -The aminopiiosptioniuin salts used in this study were sensitive to atmospheric moisture, deliquescing and subsequently hydrolyzing after only a few minutes exposure. Therefore, the starting materials v:ere stored and transferred in a D. L. Herring Model HE-^5 Dri Lab equipped with a Model HE-93 Dri Train. The products of the condensation reactions were usually unreactive to moist air. Plowever, in certain cases the products were hygroscopic in air. These materials were dried in a vacuum desiccator and stored in sealed vials in the desiccator. Benzene and petroleum ether were obtained as reagent grade materials and were dried and stored over calcium hydride. Tri-n-butylphosphine was obtained from Food Machinery and Chemical Corporation and used as obtained. Phosphorus trichloride was obtained as the reagent grade material and used as obtained. All solvents and liquid reagents were transferred by pipette to minimize exposure to moisture. 68

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69 Methods of analysis -Elemental analyses were perforcied by Galbraith Laboratories, Inc., Knoxville, Tennessee. Some nitrogen analyses were also obtained using a Coleman Model 2? nitrogen analyzer. Molecular weights were determined either by the cryoscopic method in benzene, or in benzene or chloroform solution using a Mecrolab Vapor Pressure Osmometer. The infrared spectra of materials synthesized in this study were recorded on a Beckmann Model IH-10 spectrophotometer. Solid samples were either mulled with Kujol, pressed into K3r disks, or melted on KBr plates and examined as thin films when the melting point was below 100° C. A summary of the spectral bands of new materials produced in this study between 3.'^ and 50 microns is found in Table 6. Melting points were obtained in capillary tubes using a Thomas-Hoover capillary melting point apparatus. Preparation of dialkyldiaminor>hosphonium chlorides and L(C2Hn)2P(NHp)-N=P(inip)(C2H^)2]Gl.-In the early stages of this investigation, dimetnyldiaminophosphonium chloride and diethyldiaminophosphonium chloride were prepared by the chloramination-ammonolysis of dimethylchlorophosphine and diethylchlorophosphine,^ ^ respectively. However, soon after this investigation was begun, a more convenient method was found, namely, the chloramination-ammonolysis of

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70 TABLE 6 (a) li^RARSD ABSORPTION DATA (Ca""^) C(CH,)2?N]^, KBr disk 2975(ei), 2900(m), lA-lO(m) , 1290(s), 1270(s), 1200(s,sh), 1160(vs), 1010(w,sli), 965(iii), 9^0(m), 915(s), 880(s), 855(vs), 751(m), 720(s), 685(m), 630(w), 560(21), ^90(iii), ^20(s), 568(w). [(n-C^Hg)2?N]j, melt 29^^5(s), 2920(s), 2855(m), 2500(w,b) , 1^59(w), 1^50(w), ^^rOO(w), 1562(w), 1300(w), 1260(w), 122^(m)5 1155^vs), 1085(w), 10^5(w,sh), 1000(w,b), 95^(w,b), 913(w), 889(v0, 785(w), 719(m), 660(21, Id), 505(w) , 280(vs,b). ^^^SjStrong; m, medium; w,weak; b, broad; v,very; sh, shoulder.

PAGE 79

71 tetramethyldiphosphine and tetraetnyldiphospliine. This method of preparation is discussed in detail in Chapter III. 'Hhe substance, [CCpH^)pP(2:H2)-N=P(NH2)(C2Hc)2^C;i , was prepared by the chloramination-ammonolysis of diethylchlorophosphine. ^''^ It was also obtained as a product of the condensation of diethyldiaminophosphonium chloride. Di-n-butyldiaminophosphonium chloride was synthesized by the chloramination of di-n-c :7lchlorophosphine. ^-^'^ This chlorophosphine was conveniently prepared by the method of V. H. Plets^^ ^ which involves the decomposition of tributyldichlorophosphorane (C^H.),PCl2 (C^Hg)2PCl + C.H^Gl . Tributyldichlorophosphorane can be readily synthesized by the reaction of tributylphosphine v.dth PCl;,:^ 3(C^E^)^I> 42 PCl^ -*3(C^Hg)3PCl2 + 2 P^ . In a typical experiment, 2.91 ml (33.5 mmoles) of phosphorus trichloride was dissolved in about 50 ml of dry benzene and placed under nitrogen in a Minilab reaction flask (Fig. 5). To this solution, 11.5 ml (50 mmoles) of tri-n-butylphosphine v/as added dropv;ise with stirring under a slow flow of dry nitrogen gas. The solution rapidly became deep, orange-red in color and heat was evolved. Rear the end of the addition an orange-red, amorphous solid suddenly precipitated from the mixture. At the end of the addition the mixture

PAGE 80

72 was stirred vigorously until it had cooled to room temperature (25° C). The benzene solution was removed from the precipitate by filtration and the precipitate was washed with 1-2, 25 ml portions of dry benzene and filtered, care being taken not to expose the solution to atmospheric moisture. The filtrate and washings were combined and evaporated to dryness in vacuum. The white, crystalline product, (C^Hq)-PC12» was obtained in almost quantitative yield. This material was transferred in the dry box to a 200 ml round bottomed distillation flask and heated under an atmosphere of nitrogen at about 1^0° C. Butyl chloride distilled from the mixture (b.p. 78** C) and some HCl was evolved. When the distillation of butyl chloride had ceased (1-5 hours) the mixture was cooled and distilled under vacuum. The product distilled at 57** C and 0.1 mm Hg (Lit,^^^: b.p. 0.25 = 39-^7'' C). The yield of dibutylchlorophosphine by this method was usually over 50 per cent of theory based on the amount of (C^Hq),PC12 used. The Pyrolytic Condensation of Dimethyldiaminophosphonium Chloride n[(CH,)2P(NH2)2]Cl ^iOE^)^m:i^ + n NH^Cl n = 5»^j higher In a typical experiment, 1.15 g (8.9 mmoles) of dimethyldiaminophosphonium chloride was placed in a semimicro sublimation apparatus (Fig, 15) and heated at about

PAGE 81

7? r:=o MMm Fig. 15.-Seniimicro Sublimation Apparatus.

PAGE 82

7^ 200° C and 0.2 mm Hg for three days. The resulting sublimate was removed from the cold finger under nitrogen and extracted with several portions of hot, 30-60'*, petroleum ether. The residue from this extraction was identified as ammonium chloride. Evaporation of the petroleum ether yielded a white, crystalline material with a melting range of 160-170° C. Anal . Found: C, 51.83; H, 7.98; P, ^1.15; N, 18.73. Calculated for [(CH,)2PN]: C, 32.01; H, 8.06; P, ^1.28; N, 18.66. Crude yield: 0.55 g (82% of theory). The mixture was separated into almost equal amounts of dimethylphosphonitrilic trimer and tetramer^ ^ by fractional crystallization from petroleum ether. The molecular weights (cryoscopic in benzene) were 220 (calculated: 225) and 311 (calculated: 500), respectively. The trimer melted with sublimation at 187-190° C (Lit:^^^^ M.P. 195-196° C) and the tetramer melted with sublimation at 157160° C (Lit:^^^^ M.P. 163-16'<-° C). The infrared spectra of these compounds agree with the assignments reported by Searle.^2^^ The Synthesis of Highly Polymeric Dimethylphosphonitrile In several pyrolyses of dimethyldiaminophosphonium chloride, described above, a trace of a black, glassy residue was observed in the sublimation pot at the completion of the sublimation of ammonium chloride and [(CH,)2PN], I,, This material melted in the range of 1561^6° C and was not visibly sensitive to moist air. Anal .

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75 Found: C, 51.81; H, 8.16; N, 18.79; P, ^1.1^; Mol. Vt., 764-0 (Mol. Vt. of a (CH,)2PN-unit, 75). Thus, it was discovered that the pyrolytic condensation of dimethyldiaminophosphonium chloride produces trace amounts of C(CH,)2PN] where n is a large number. The yield of high polymer could be increased considerably by mixing the starting phosphonium salt with finely divided ammonium chloride produced by the gas phase reaction of chlorine and ammonia. In a typical experiment the phosphonixim salt and a weighed amount of ammonium chloride were thoroughly mixed in the dry box, placed in a semimicro sublimation apparatus and pyrolyzed as before. The dimethylphosphonitrilic trimer and tetramer and ammonium chloride sublimed to the cold finger and were separated as before. The high polymer remained in the sublimation pot and was either scraped from this vessel or removed by dissolving it in benzene. The effect of ammonium chloride on the distribution of products of this reaction is shown in Table 7. The infrared spectrum of the crude polymer is shown in Figure l'^-. The high polymers so formed were usually soluble in hot benzene and chloroform. In some cases a residue was observed which swelled in benzene but did not dissolve. Extraction^"'' -^ of the crude material with cyclohexane produced, upon evaporation of the solvent, a white powder melting at 159-1^5° G and having a molecular weight of from

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76 TABLE 7 SFFECT OF AMnONIUM CHLORIDE ON PRODUCT DISTRIBUTION Vt. % of NH^Cl in Recovered Recovered Starting Material Yield of Polymer, Yield of [(CH,)^PN], ^ ^.5 82 trace ^.2 82 trace 6.9 79 5.6 13.6 56 9.9 32 ^2 10.4 52 17.4 14.4 44 20 11.2 68

PAGE 85

77

PAGE 86

78 3500 to 9000 depending on the sample used. The residue from the cyclohexane extraction was soluble in benzene, melted at 1$6-138<» C and had a molecular weight of 12,500. Thermal gravimetric analysis^ •^-^'^ (using an Aminco Thermograv, American Instrument Co.) of a sample with an average molecular weight between 8000 and 9000 was obtained using a 100 cc/min flow of helium at a rate of temperature increase of 3°/niin. This analysis showed no weight loss up to 300° G, and a rapid loss of weight from 300* to 500° C during which essentially all of the sample sublimed from the apparatus as low-molecular-weight cyclic material, principally trimer and tetramer. Differential thermal analysis was carried out on this material ^^'''^ in helium using a heating rate of ^° /mln with AloO^j as a reference. A sharp endotherm was observed at 142° (M.P. of sample: 1^3-1^5° C) and a broad exotherm was observed starting at about 300° C, the latter presumably resulting from the onset of thermal decomposition. The Pyrolytic Condensation of Diethyldiaminophosphonium Chloride 2[(C2H5)2P(NH2)2]C1 [(C2H^)2P(NH2)-N=P(NH2)(C2H^)2]C1 + NH^Cl [(C2H^)2P(NH2)2]C1 + [ (C2H^)2P(NH2-N=P(NH2)(C2H^)2]C1 -* C(C2H^)2PN]5 + 2 NH^Cl

PAGE 87

79 In a typical experiment, 0,99 g (6.5 mmoles) of diethyldiaminophosplionium chloride was placed in a semimicro sublimation apparatus and heated to about 180° C and 0.2 mm Hg for five days. This process produced a white sublimate as well as a substantial amount of light-colored residue. The residue was dissolved in boiling benzene and filtered. Upon evaporation of the benzene a white, crystalline material was recovered which melted at 61-6^4-° C; yield, 0.30 g. This material is hygroscopic, water-soluble and gives a CItest with aqueous AgNO,. Anal . Found: N, 16.5. Calculated for [(C2Hc)2P(NH2)-N=P(NH2)(C2Hn)2]Cl : N, 16.18. The infrared spectrum of this material was identical with that of [(C2H^)2P(NH2)-N=P(NH2)(C2H^)2]C1 (M.P. 58-61*' C) produced by chloramination-ammonolysis of di ethyl chl or ophosphine. ^'^'^ The nuclear magnetic resonance data for [(C2Hc)2P(NH2)-N=P(NH2)(C2Hc)2^Gl, not included in the earlier reference, ^-^'^ provides some interesting additional information about the structure of this substance. The proton magnetic resonance spectrum (Fig. 15) was run on a Varian high resolution spectrometer at 56.^ Mc using a CDCl, solution. The spectrum was obtained by sweeping 5 slowly through the field and interchanging the reference, acetaldehyde, with the sample. Peak A refers to the NH2 protons, peak B to the methylene protons and peak C to the methyl protons. The usual methylene quartet and methyl

PAGE 88

80 J o p-i OJ /~~\ LPS CM o C\J OJ OJ LTN W C\J O o 3 Ph -P O (1) ft CO !2; I bO •H

PAGE 89

81 triplet are further split by spin-spin coupling with the phosphorus atoms. The spectrum is consistent with the structure^ ^ im2 ITH2 CpHc1 I ^CpHq c J T* ' • * PI ' * ' P ^ C2HC ^2^5 01 H-H

PAGE 90

82 was carefully resublimed at about 50° G and 0.1 mm Hg. The sublimate melted at 109-112° C. Anal. Found: C, 46.59; H, 9.92; P, 50.30; N, 15.^9; Mol. Wt. 505. Calculated for [(C2H^)2PN]j: C, 46.60; H, 9.78; P, 50.04; N, 15.59; Mol. Wt. 509. Yield: 0.21 g (55% of theory). The infrared spectrum of this material agreed with the assignments listed (25") in the literature ^ for diethylphosphonitrilic trimer. The literature value for the melting point of the trimer is 117.5-119° C. The residue from this sublimation was recrystallized from benzene and identified as the intermediate, [(C2Hc)2P(NH2)-N=P(NH2)(C2Hc)2l01. The total yield of this intermediate was 0.54 g (41% of theory). The Pyrolytic Condensation of [(C2H^)2P(NH2)-N-P(NH2)(C2H^)2]C1 [(C2H5)2P(NH2)-N=P(M2)(C2H^)2]C1 li^^^)'^^^-^^ ^t, + NH^^l In a semimicro sublimation apparatus, 0.85 g (5.5 mmoles) of [(C2Hc)2P(NH2^"^"-^^^2''^^2^5^2^^-'^^^ heated at about 200° C and 0.15 mm Hg for 4-5 days. This process produced a white, oily sublimate and a trace of black residual ash. The sublimate was extracted with several portions of petroleum ether. The residue from this extraction was again extracted with several portions of hot

PAGE 91

83 benzene. Prom the benzene solution, 0,25 g (0.96 mmoles) of unreaoted starting material was recovered. From the petroleum ether solution, 0.56 g (75% of theory based on the starting material actually reacted) of a mixture of diethylphosphonitrilic tetramer and trimer was recovered by evaporation. The final residue of the solvent extractions consisted of ammonium chloride. The mixture of diethylphosphonitrilic tetramer and trimer was separated by repeated fractional sublimation at 53° C and 0.1 mm Hg. By this method the mixture was found to consist of about 20 per cent trimer (M.P. 110-11^° C) and 80 per cent tetramer (a viscous oil^ ). Anal. Found: 0, ^6.36; H, 9.76; P, 29.8^; N, 13-30; Mol. Wt. ^01. Calculated for [ (C2H^)2PN]^: C, ^6.60; H, 9.78; P, 30.0^; N, 13.59; Mol. Wt., ^12. The infrared spectrum of this material agrees quite well with the assignments listed in the literature^ ^"^ for diethylphosphonitrilic tetramer. The Pyrolytic Condensation of Di-n-butyldiaminophosphonium Chloride 3[(n-C^H^)2P(NH2)2]Cl [(n-C^Hg)2PN] ^ + 3 NH^Cl Di-n-butyldiajiiinophosphonium chloride (1.08 g or 5 mmoles) was placed in a semimicro sublimation apparatus and heated at 190° C and 0.1 mm Hg for four days. A white sublimate was observed. Only a trace of black residue

PAGE 92

8^ remained in the pot at the completion of the reaction. The sublimate was extracted with 30-60" petroleum ether. The insoluble residue was shown to be ammonium chloride. Evaporation of the petroleum ether yielded a white wax which melted at ^5-50° C and sublimed readily at 70° C and 0.1 mm Hg. Anal. Found: C, 60.09; H, 11.57; P, 19.23; N, 8.90; Mol. Vt., ^70. Calculated for [(C^Hq)2PN], : C, 60.35; H, 11.^0; P, 19.^5; N, 8.80; Mol. Vt. , 478. Yield: 0.77 g (95% of theory). The infrared spectrum of dibutylphosphonitrilic trimer is shown in Figure 16. Discussion The results of this study show that diaminophosphonium chlorides can be easily converted by pyrolytic condensation to phosphonitrilic derivatives. The yields observed in such a process are essentially quantitative. The pyrolytic condensation of dimethyldiaminophosphonium chloride produces amounts of dimethylphosphonitrilic trimer and tetramer. These compounds were separated from the byproduct, ammonium chloride, by their solubility in petroleum ether, and the trimer/tetramer mixture was separated by fractional crystallization from petroleum ether. The materials were identified by elemental analysis, molecular weight determinations and comparison of their infrared spectra with published infrared data.^ ' When finely

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85 o o o o o o

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86 divided ammonium chloride was mixed with the starting material, pyrolysis produced a new compound identified as highly polymeric dimethylphosphonitrile. This material is a polymer of the formula, -t P=N— i, where n varies from 50 to 150. It was characterized by elemental analysis, molecular weight determinations, infrared analysis, thermal gravimetric analysis and differential analysis. The infrared spectrum of this material (Fig, 1^) is somewhat similar to that of the cyclic trimer or tetramer having C-H stretching and deformation peaks at 2970 cm" and at 1^10 cm" , respectively. Two peaks occur at 1290 and 1270 cm which are attributed to P-CH^ bonding. ^^^-^ The "P=N" stretching band exhibits a broad, strong shoulder at about 1200 cm" and a strong peak at 1160 cm" . There are several peaks in the region from 850 cm" to 965 cm" and from 685 cm" to 755 cm" . Peaks in this region are generally attributed to "P=N" elongation and "P-N=P" deformation. ^^^'^^^ Definite assignments for these peaks cannot be made at the present time. Yields of the polymer as high as 52 per cent of theory were obtained when mixtures of about 10 per cent finely divided ammonium chloride and 90 per cent dimethyldiaminophosphonium chloride were pyrolyzed. The pyrolytic condensation of diethyldiaminophosphonium chloride produces the primary condensation product.

PAGE 95

87 [(C2Hc)2P(^2^~^~^^^'^2^^^2^5'^2-^^-'^^^^^ ^^^ recovered in about ^0 per cent yield, and diethylphosphonitrilic trimer, [(CpHc-)pPN] ^ which was recovered in about 30 per cent yield. The first condensation product was shown by elemental analysis and infrared analysis to be identical with [(C2H^)2P(NH2)-N=P(NH2)(C2K^)2]C1 produced by the chloramination-ammonolysis of diethylchlorophosphine. '^ Diethylphosphonitrilic trimer was identified by elemental analysis, molecular weight determination and comparison of its infraC25) red spectrum with published infrared data. ^ The pyrolytic condensation of the intermediate, [(C2Kn)2P(NH2)-N=P(NH2)(C2Hc)2]Cl, produces a mixture of diethylphosphonitrilic trimer and tetramer which was recovered in about 75 per cent yield. The phosphonitrilic mixture, consisting of about 80 per cent tetramer and 20 per cent trimer, was separated from the byproduct, ammonium chloride, by its solubility in petroleum ether. The trimer aoid tetramer were then separated from each other by repeated, fractional vacuum sublimation. In this case, the trimer was slightly more volatile than the tetramer and a separation could be made. The pyrolytic condensation of di-n-butyldiaminophosphonium chloride produces a nearly quantitative yield of a new material identified as di-n-butylphosphonitrilic trimer, [ (n-C^HQ)2PN],. This material was char^-cterized by

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88 elemental analysis, molecular weight determination and infrared analysis. The infrared spectrum of this material (Fig. 16) has the usual C— H stretching and deformation peaks in the region of 2950-2850 cm"-*and 1^50-1570 cm"-"", respectively.. Bands attributed to skeletal -CHpvibrations occur at 1^00 cm , 1300 cm" and at 1260 cm" . A sharp peak is observed at 1215 cm" which may be attributed to P-G bonding. The "P=N" stretching peak occurs at 1155 cm" . Of all the phosphonitrilic derivatives for which this peak has been measured, it occurs at the lowest energy in this derivative. This is to be expected because the butyl groups have little, if any, electron attracting ability. Thus, they are unable to cause appreciable delocalization of the nitrogen lone-pair electrons into the region of the P-N bond. The remainder of the spectrum between 1155 cm" and 650 cm" contains several peaks of weak intensity, some of which may be attributed to skeletal vibrations of the butyl groups. Others lie in the region assigned to "P=N" deformation peaks, "P-N=P" stretching peaks and ring breathing vibrations. We can make no definite assignments in this region at this time. This study establishes the fact that dimethyldiaminophosphonium chloride, diethyldiaminophosphonium chloride, di-n-butyldiaminophosphonium chloride and [(C2Hc)2P(^2^"^~^^^^2^^^2^5^2^^-^ ^^® convenient phosphonitrilic precursors, giving excellent yields of cyclic

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89 phosplionitrilics under pyrolytic conditions. Combined with the findings of Chapter III, this study constitutes an important part of a new method of synthesis of such derivatives from substituted diphosphines, chloramine and ammonia. The results of this investigation have provided very convincing evidence in favor of the step-wise reaction sequence postulated^ ^ earlier in which the then unknown diaminophosphonium ion, RpPCNHp)^© , was considered to be a reactive intermediate leading to phosphonitrilic derivatives. The case in point is the pyrolysis of diethyldiaminophosphonium chloride. The only products of this reaction are [(C2Hn)2P(NH2)-N=P(NH2) (C2H^)2]C1 and [(CpH(-)pPN],. Indeed, these are the expected products if one assumes the following sequence 2[(C2H^)2P(NH2)23C1 [(C2H^)2P(NH2)=N-P(NH2) (C2H^)2]C1 + NH^Cl [(C2H^)2P(NH2)2]C1 + [(C2H^)2P(NH2^~^^^^^2^^^2^5^2^^^ -* [(C2H^)2PN]j + 2 NH^Cl The pyrolysis of the intermediate, [(C2Hc)2p(NH2)-N=P(NH2)(C2Hc)2^Cl, produces chiefly diethylphosphonitrilic tetramer. Some cleavage of the intermediate does occur, however, resulting in the formation of diethylphosphonitrilic trimer and some decomposed material.

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90 One of the most interesting results of this study was the discovery and characterization of highly polymeric dimethylphosphonitrile. This discovery has attracted interest for several reasons. First of all, despite all the previous work in phosphonitrilic chemistry, there is a paucity of information concerning the synthesis of thermally stable and unreactive high polymers with the repeating unit -E — ^P=N-^ (See Chapter II). This method of synthesis is one of the few which results in a phosphonitrilic high polymer which is soluble in common solvents, which can be molded mechanically and which is relatively unreactive toward moisture and oxygen. In addition to exciting academic interest, this method may also prove valuable in the synthesis of commercially useful polymers. Although the polymeric material synthesized in this study has some disadvantages in its ready solubility, low melting point and thermal instability above 300° 0, films of the substance can be cast which have reasonable strength. ^"^-^ The dimethylphosphonitrile is isoelectronic with dimethyl siloxane, — E Si 0-9-, the basic unit of an inorganic polymer system which has enjoyed such wide use in recent years that its parent, (CH^)2SiCl2, is now produced commercially in large quantities. If the isoelectronic relationship is any indication of chemical

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91 and physical similarities whicTi may exist in these two systems of inorganic polymers, then there is a possibility that the process discovered in this study may become commercially important in the future. It is interesting to note that the yield of high polymers from the pyrolysis of dimethyldiaminophosphonium chloride seems to depend on the amount of ammonium chloride mixed with the starting material (Table ?)» under similar conditions of temperature, pressure and time. The postulated first step of the condensation process, 2[(CKj)2P(NH2)2]Cl [(CHj)2P(NH2)-N==P(NH2) (CH,)2]C1 + NH^Cl , has been confirmed in the pyrolysis of diethyldiaminophosphonium chloride. Since the actual mechanism of condensation is not clearly known, any statement concerning the mechanism of the effect of ammonium chloride on the first step or subsequent intermolecular condensations would be highly speculative. However, in view of the fact that the cyclic dimethylphosphonitriles are weak bases, ^ '^ it is conceivable that in the molten reaction mixture a proton transfer could occur between ammonium chloride and a ring nitrogen. This could result in the breaking of a P— N bond and the formation of a -?© species which could attack other ring-nitrogen

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92 atoms and lead to linear products. For instance, the attack could occur on a cyclic trimer R R ;N N: R ;N X R /R + He R R >% © N:H » N' R R R R \ / \ / R R R R r \ / \ / R R ) % R R R R R -* HN=§=P— N ]r P © , etc. N' This is similar to the mechanism postulated by Allcock and Best^-^ ^ for the polymerization of [PNCloJz zf (see page 21). The polymer formed is not highly cross-linked and therefore undergoes almost complete depolymerization to cyclic derivatives in the 300-500° range. There are two suggestions which we can make for further work in this area. Both suggestions are concerned with the formation of high polymers. The effect of ammonium chloride on the pyrolytic condensation of diaminophosphonium chlorides was investigated only in the case of dimethyldiaminophosphonium chloride. This effect should be studied

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93 with other diaminophosphonium chlorides in order to investigate its general applicability in the synthesis of an homologous group of [Ro^^^ polymers. Secondly, the effect of i^H.Cl on cyclic phosphonitrilic derivatives, [RoPN];, ^, should be investigated under various conditions in order to test the validity of the polymerization mechanism proposed ab ove . Summary The pyrolytic condensation of dimethyldiaminophosphonium chloride produces in high yield the known phosphonitrilic derivatives, [(011^)2?^]^ ^> and a new material identified by elemental analysis, molecular weight determination and infrared spectrum analysis as the substance, -^ p=:N-3, where n varies from 50 to 15O. When finely divided ammonium chloride is mixed with the starting material the yield of high polymer is increased. The highest yield of polymer (52%) was produced by a mixture consisting of about 10 per cent ammonium chloride and 90 per cent dimethyldiaminophosphonium chloride. A possible polymerization mechanism is put forward to explain the effect of ammonium chloride on this system. The pyrolytic condensation of diethyldiaminophosphonium chloride produces the known compounds.

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9^ yield. This reaction illustrates the step-wise nature of the reaction sequence leading from diaminophosphonium chlorides to phosphonitrilic derivatives. The pyrolytic condensation of [(C2H^)2P(NH2)-N=P(NH2)(C2Hn)2]Cl produces a mixture of the knov;n phosphonitrilic derivatives, [(CpHi-)^?^]^ ^. This mixture consisted of about 80 per cent tetramer and 20 per cent trimer, and was recovered from the reaction in about 75 per cent yield. The pyrolytic condensation of di-n-butyldiaminophosphonium chloride produces a new phosphonitrilic derivative, [(n-C^Hq)2PN]z, in nearly quantitative yield. This material was characterized by elemental analysis, molecular weight determination and infrared analysis. The characteristic "P=N" stretching peak in this material occurs at 1155 cm"-'-. This study confirms the reaction sequence postulated earlier^ ^ for the formation of phosphonitrilic derivatives by condensation of diaminophosphonium chlorides. It also provides a new method for the formation of a highly polymeric phosphonitrile, and thus may become important as a general synthetic procedure for such inorganic polymers.

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CHAPTER V THE REACTION OF DIALKYLDIAMINOPHOSPHONIUM CHLORIDES WITH TRI-, TETRA-, AM) PENTACHLOROPHOSPHORANES Experimental Manipulation of materials , -The dialkyldiaminophosphonium ciilorides and the chlorophosphoranes used in this study are rapidly hydrolyzed in the presence of water and were stored and transferred in a D. L. Herring Model-'4-3 Dri Lab equipped with a Model HE-93 Dri Train. Strict precautions were taken to avoid contamination of solvents and other reagents by moisture. All solvents were obtained as the reagent grade products. Carbon disulfide was dried and stored over PpOc. All other solvents were dried and stored over calcium hydride. Triethylamine was obtained as the technical product and dried and stored over calcium hydride, Methyldichlorophosphine was obtained from Food Machinery and Chemical Corporation and was used as obtained. This material was stored and transferred by pipette in the dry box. Tetramethyldiphosphine was prepared by the desulfuration of tetramethyldiphosphine disulfide with tributyl phosphine, as described in Chapter III (page 56). 95

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96 It was purified by distillation and stored in the dry box. Pbosphorus pentachloride was obtained as tbe reagent grade product and was used as obtained. Dimethjldiaminopbosphonium chloride and diethjldiaminophosphoaium chloride were obtained by chloramination-ammonolysis of the corresponding diphosphines . This method is described in Chapter III. Hethods of analysis . -Infrared spectra of the materials produced in this study were obtained using either a Beckmann Model IR-10 grating infrared spectrometer or a Perkin-Elmer Model 537 grating infrared spectrometer. Solid samples were either mixed with KBr and pressed into pellets or mulled with Nujol and examined between KBr disks. In certain instances thin films of material could be obtained by carefully evaporating a chloroform solution of the sample on a KBr disk. Samples of substances which were sensitive to moist air were prepared for infrared analysis in the dry box. A summary of the spectral bands of these materials between 2.5 and 25 microns is presented in Table 9. Elemental analyses and molecular weight determinations were performed by Galbraith Laboratories, Inc., Knoxville, Tennessee. Several nitrogen analyses were carried out in these laboratories using a Coleman Model 29 Nitrogen Analyzer. For the compounds CH^PCl^ and (CH,)2PClj the

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97 TABLE 9^^^ INPHARED SPECTRAL DATA, Cm"-'CH^PCl^, Nujol 2900(vs), 28^0(vs), 1^55(vs), 1375(s), 1298(w), 1275(21), 1259(ni), 1195(w), 11^0(w,b), 1065(w), 920(vs,b), 890(vs,b), 788(s), 735(w,sh), 720(ni), 505(vs,b), 5^2(m), 492(w,b), 47^(m,sh), ^67(s). (CH^)2PClj, Nujol 3210(w), 5125(w), 2920(vs), 2850(vs), 2760(s), 2700(w,sh), 2650(w,sh), 2575(w) , 2370(w), 23^0(w), 2310(w), 2260(iii), 22^9(iii), 2210(m) , 2170(vO, 20a0(w), 1659(s,b), 1580(vw), 1505(w,b), 1^55(vs), 1^05(s), 1397(vs), 1379(vs), 1565(s,sii), 1305(s), 1290(vs), 1250(w), 11^0(w,b), 1065(w), 966(vs), 9^0(vs), 900(vs), 880(w), 780(w,sli), 760(ni), 7^6(vs), 579(vs), 500(s). (GHj)2Cl^PjNj, Nujol 29^0(vs,b), 2850(vs), 2715(w), 2665(w,b), 2299(w,b), 22^5(w), 2175(w), 21^^(w), 2085(w), 2020(m), 1996(w,sh), 1960(w), 1939(w) , 187^(w), 1869(w), 1805(w), 1766(w), 1651(w), l^^O(vs), 1^18(s), 1^05(m), 1380(vs), 1365(s), 1308(vs), 1295(vs), 12^2(s,sli), 1220(vs), 1170(vs), 962(s), 935(s), 905(w), 881(vs), 876(s), 787(s). 758(s), 722(w), 69^(s), 67^(w), 63^(vs), 58^(vs,b), 510(vs,b), ^31(w), ^O^(vs). [(CH^)2PN.(CH,)C1PN]^, Film 2899(vs,b), 260^(s), 1650(w,b), 1^05(s), 1305(vs,b), 1220(vs,b), 990(vs,s]a), 971(vs,sli), 935(vs,b), 881(vs), 819(s,b), 7^9(s), 682(w), 678(w,sh), 6&2(in), 6^9(w,sli), 521(w,sb), ^88(b,sli), 467(s).

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98 Table 9 (cont'd) [(C2H^)2PN-C12PN]2, KBr 2959(ni), 2920(m), 2890(w), 2860(in), 1455(m,sh), 1^^4(m), 1595(w), 1278(s), 1200(vs,1d), 1150(vs), 1050(w), 10C9(s), 821(s), 788(w), 750(^v) , 720(m), 677(w,sli), 565(w), 650(vO, 610(s), 561(vs), 525(w), ^89(vs), 407(w), i^OO(w,sh), 375(m). Ca") ^ '^s, strong; m, medium; w,weak; b, broad; v,very; sh, shoulder.

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99 sampling technique of Galbraith Laboratories was not refined enough to prevent hydrolysis of the samples prior to analysis, Therefore, these materials could only be characterized by chloride analysis carried out in these laboratories. The samples were first transferred to weighed vials in the dry box. The weighed samples were then submerged, vials and all, in a hydrolyzing solution consisting of 25 ml of ethanol and 10 ml of 10 per cent NaOH. The analysis was then carried out by the usual Volhard procedure. This method was sufficient for the identification of the compounds; however, the values obtained were always slightly higher than theoretical.^'^'' Melting points were determined in a Thomas-Hoover capillary melting point apparatus using tubes sealed with wax under nitrogen. Preparation of CH;,PC1^ and (CH;,)2PC1,.-The information to be found in the literature on these compounds is scant, and in certain cases, erroneous. Methyl tetrachlorophosphorane, erroneously reported to arise from the chlorination of tetramethyldiphosphine disulfide,^ ^ was synthesized by chlorination of methyldichlorophosphine in CSp at about 0° C.^^ Similarly, dimethyl trichlorophosphorane was synthesized by the method suggested by Issleib and Seidel,^ '^ namely, the chlorination of tetramethyldiphosphine.

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100 The same general procedure was used in the synthesis of both compounds. Into a 200 ml, 5-n.eck round-bottom flask equipped with a gas entry tube, a thermometer and a condenser leading through a liquid Np trap to the atmosphere, v/as placed the substance to be chlorinated and 50 ml of solvent. With this volume of material, the gas entry tube was well above the surface of the solution, thus avoiding dangerous plugging of the chlorine line. The solution was cooled with an ice and salt bath. Chlorine gas was introduced and metered with a previously calibrated rotameter at the rate of approximately 0.9 mmoles/min. The temperature of the magnetically stirred solution could be controlled somewhat by varying the rate of chlorine addition. The temperature was maintained at near 0° G and was never allowed to exceed 10° G. White, crystalline products formed immediately and precipitated from the respective solutions. The chlorination was stopped before the theoretical amount of chlorine had been introduced to prevent possible chlorination of the methyl groups which sometimes occurs with excess chlorine. The solution was then filtered in the dry box and the crystalline product was washed with additional, fresh solvent and dried in vacuum. Since both chlorophosphoranes react violently with water, they were stored in sealed vials in the dry box until needed.

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101 In a typical experiment, 5 ml (50 rjnoles) of methyldichlorophosphine v;as dissolved in 50 ml of CSq* cooled to about 0° C and chlorinated for 55 minutes. The white, orystallin© product melted sharply with decomposition at 139.5° C. Anal. Found: CI, 75.2. Calculated for CH^PCl^: CI, 75.5. Yield: 6.95 S (75% of theory based on chlorine used). The infrared spectrum of methyltetrachlorophosphorane is shown in Figure 17. Similarly, 2 ml (14.2 mmoles) of tetramethyldiphosphine was dissolved in 50 ml of toluene, cooled to about 0° C, and chlorinated for A-0 minutes. The white, crystalline product melted sharply with decomposition and sublimation at 19^.5-195° C. Anal. Found: CI, 56.7. Calculated for (CH^)2PCl5: CI, 65.5. Yield: 2.72 g (58% of theory based on chlorine used). The infrared spectrum of dimethyltrichlorophosphorane is shown in Figure 18. The Reaction of Dimethyldiaminophosphonium Chloride with PClr In a typical experiment, 1.06 g (8.25 mmoles) of dimethyldiaminophosphonium chloride was mixed with 1.72 g (8.25 mmoles) of PCln in a 100 ml round-bottom flask equipped with a reflux condenser and a side arm for introduction of nitrogen. Benzene (25 ml) was added as a solvent and the mixture was refluxed. A slow flow of dry nitrogen was

PAGE 110

102 o o «.o

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103 LPs 00 O O LA OJ LA 00 CV O

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lOApassed over the mixture and then bubbled through a benzene solution of trie thyl amine at a rate of about 15-20 bubbles/min (less than 1 J2./min). HCl was evolved immediately from the refluxing mixture and collected in the triethylamine solution as the solid hydrochloride. After about three days of reaction, 3.86 g (85% of theory assuming all N-H hydrogen in [(CH^)2P(M2^2-'^"^ appears as HCl) of triethylamine hydrochloride had been recovered and the rate of evolution of HCl from the reaction mixture was negligible. The clear benzene solution was evaporated to dryness in vacuum, yielding 1.56 g of crude product. This material was highly hygroscopic giving off HCl readily in moist air. Sublimation of this material at about 50° C and 0.15 Dim Hg yielded 0.75 g of white sublimate and 0.81 g of a hard, plastic residue. The sublimate was further purified by several recrystallizations from benzene and hexane and repeated sublimations at about 50° C and 0.1 mm Hg. FI.P, 17^-176° C (sub.). Anal. Pound: C, 8.05; H, 2.20; N, 1^.07; P, 29.55; CI, A-6.07; Mol. Wt., 508. Calculated for (CH^)2Cl^PjNj: C, 7.85; H, 1.97; N, 15.70; P, 30.28; CI, 46.22; Mol. Wt., 307. The infrared spectrum of this material is shown in Figure 19. The yield of this substance varied considerably in several experiments. The crude yields ranged from 25 per cent of theory to about 60 per cent of theory (based on PClc used). The reaction was also

PAGE 113

105 a] vO

PAGE 114

106 attempted with a 2:1 ratio of PClc to [(GH;,)2P(NHp)p]Cl. In this case the evolution of HCl was very rapid but only a 5 per cent yield of crystalline material could he extracted from the extremely air-sensitive, oily product. The residue from the sublimation was a creamcolored, glassy substance which was extremely sensitive to moist air. In some cases this material was oily instead of solid. Vacuum pyrolysis of the crude reaction mixture at 180-190° C and 0.1 mm Hg in a semimicro sublimation apparatus produced a sublimate as described above. The residue from this pyrolysis, however, was a grey-brown glass which did not appear to be affected by exposure to moist air. The glass was infusible up to 500° G and was insoluble in all solvents tried. The infrared spectrum of this material consisted of several broad bands, one of which occurred at 1250 cm" indicating that the material has phosphonitrilic "p=!T" bonds. Analytical data indicate the following atomic ratios, C:H:P:N = 1.0:3.5:1.0:1.5. These numbers at least indicate the unit, [(CH,)2PN*Cl2PN]^; however, the largest C1:P ratio found was about 1:5 indicating a loss of chlorine, perhaps through cross-linking.

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107 The Reaction of Siethyldiaminophosphoniuni witli PCln In a typical experiment, 0.92 g (5.8? mmoles) of diethyldiaminopb,ospb.onium chloride was mixed with 1.22 g (5.87 mmoles) of PClc in a 100 ml round-bottom flask equipped with a reflux condenser and a side arm for introduction of nitrogen. Benzene (25 ml) was added as a solvent and the mixture was refluxed. A slow flow of dry nitrogen was passed over the refluxing mixture and then bubbled through a benzene solution of triethylamine at a rate of 15-20 bubbles/min (less than 1 £/min) . After about five days of reflux, 2.53 g (18.^ mmoles; 78.4% of theory assuming all N-H hydrogen in [(02^-0^) ^^('^ 2^ 2^^-^ appears as HCl) of triethylamine hydrochloride had been recovered and the rate of evolution of HCl from the refluxing mixture had become negligible. The reaction was pushed to completion by the addition of 2-5 ml of dry triethylamine to the reaction mixture. Triethylamine hydrochloride precipitated from the solution and was removed by filtration. The clear benzene solution was then evaporated to dryness in vacuum yielding an oily solid which was extremely sensitive to moist air. This mixture was separated by sublimation at 40-50° C and 0.25 mm Hg. The white, crystalline sublimate so formed melted in the range of 120-125° C. Several recrystallizations of this material from acetonitrile and

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108 ber.zene and repeated sublimation at 50° C and 0.1 mm Hg raised the melting range to 12^-130° C (sub.). Anal. Found: C, 18.22; H, 4.08; P, 26. 9^; N, 12.52; 01, 31.8; Mol. Vt., $35. Calculated for [(C2H^)2PN'Cl2PN]2: C, 21. 9^; H, i^.50; P, 28.29; N, 12.79; 01, 32.4; Hoi. Wt., 438. The infrared spectrum of this material is shown in Figure 20. The yields of this material in several experiments were quite low, ranging from 5 to 15 per cent of theory based on [(C2Hi-)2P(NH2^2-'^''"* ^^® material seemed to be subject to slov/ hydrolysis in moist air, and further purification could not be accomplished. The residue from the sublimation was a dark brown oil which fumed in air. In subsequent experiments the crude reaction mixture was pyrolyzed in a semimicro sublimation apparatus at 200-220° C and 0.1 mm Hg. The sublimate was similar to the sublimate described above, melting at 124-150° G and having a similar analysis. The residue, however, was a brown, glassy material which was apparently not affected by moist air. This material undergoes decomposition at 240-250° C and is insoluble in all solvents tried. Anal. Found: G, 24.31; H, 6.23; P, 31.22; N, 12.95. This analysis gives a C:P ratio of 2:1 and a P:N ratio of 1:0.9, indicating the formulation, [(C2Hc)2PN.Gl2PN] , for which the calculated analysis is: G, 21.94; H, 4.60; P, 28.29; N, 12.79. If the found

PAGE 117

109

PAGE 118

110 analysis is subtracted from 100 per cent and the difference is assumed to be percent CI, the P:C1 ratio is 1:0.7. This is slightly less than the expected ratio of 1:1 and may indicate cross -linking. The infrared spectrum of this material is consistent for a polymeric material, consisting of several broad bands. One broad peak occurs at 1225 cm" and could be attributed to the phosphonitrilic "p=l:T" stretching. Another broad peak is observed at 450 cm~\ the region associated with P-Cl vibrations. The Reaction of Dimethyldiaminophosphonium Chloride with Methyltetrachlorophosphorane Dimethyldiaminophosphonium chloride (0.88 g; 6.82 mmoles) was mixed with 1.31 g (7.0 mmoles) of methyltetrachlorophosphorane in a 100 ml round-bottom flask equipped with a reflux condenser and a side arm for introduction of nitrogen. Benzene (25 ml) was added as a solvent and the mixture was refluxed for seven days. A slow stream of dry nitrogen was passed over the refluxing solution and bubbled into a benzene solution of triethylamine at the rate of 15-20 bubbles/min (less than 1 ji/min). At the completion of the reaction, 26.8 mmoles (98% of theory assuming all N-H hydrogen from [(CH,)2p(NH2^2-'^-'' ^PP®^^^ as HCl) of triethylamine hydrochloride had been recovered. The clear benzene solution was cooled and evaporated to

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Ill dryness in vacuum. The product was a white solid which was extremely sensitive to moist air. This material was transferred in the dry box to a semimicro sublimation apparatus and heated at 170-185° C and 0.1 mm Hg for four days. The resulting sublimate was shown to be mostly ammonium chloride. The residue was a red-brown, glassy substance which melted at 97-107° C. This material was soluble in chloroform, insoluble in benzene and soluble in water, apparently hydrolyzing on contact with it. Upon exposure to moist air the material turned wet immediately and underwent hydrolysis. Thin, transparent films of the material could be cast by careful evaporation of chloroform solutions. The infrared spectrum of such a film is shown in Figure 21. Anal . Found: C, 20. 2^^-; H, 5.^9; P, 51.92; N, 1^.50; CI, 21.25; Nol. Wt., 915. Calculated for [(CH^)2pN-(CHj)ClPN]^: C, 21.15; H, 5-52; P, 56.55; N, 16.^3; CI, 20.79; Kol. Wt., 170.5/unit. Attempts to improve the P and F analyses by using the Kjeldahl method failed, presumably because the sample hydrolyzed prior to analysis. However, the P:1T ratio was 1:1 indicating a phosphonitrilic structure. The other atomic ratios are close to those required by the formula postulated above: C1:P =1:1.7; C:P = 3:1.8; C:H = 1:5.2; CI : C = 1:2.8. Yield: 0.81 g (70% of theory based on the formula [ (CHj)2pN(CH^)CIPN] ) .

PAGE 120

112 t— I CM CO CM d H X n^ CO

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115 The Reaction oi Dimethyldiaminophosphonium Chloride with Dimethyl trichlorophosphorane Dimethyldiaminophosphoaium chloride (0.57 S; 5.2 mnoles) was mixed with 0.90 g (5»^ mmoles) of dimethyl trichlorophosphorane in a 100 ml round-hottom flask equipped with a reflux condenser and a side arm for introduction of nitrogen. Benzene (25 ml) was added and the mixture was refluxed. A slov; stream of dry nitrogen was passed over the refluxing mixture and bubbled through a solution of triethylamine in benzene at a rate of 15-20 bubbles/min (less than 1 j2/min). After about four days of refluxing, only 70 per cent of the theoretical HGl had been evolved and reaction had ceased. The solvent was evaporated to dryness in vacuum and replaced by dry chlorobenzene (B.P. 130° C). Hefluxing in this solvent did not produce more HCl, however. Finally 0.9 ml (about 6 mmoles) of dry triethylamine was added to the reaction mixture and refluxed for one hour to push the reaction to completion. Triethylamine hydrochloride precipitated and was removed from the benzene solution by filtration. The total amount of triethylamine hydrochloride recovered was 2.56 g (18.5 mmoles; 90% of theory assuming all IT-H on [iGE^)2^(.l^'^2^2^^-^ appears as HGl). The clear solution was then evaporated to dryness yielding an oily solid. This mixture was separated by sublimation at 50° C and 0.1 mm Hg. The crude

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11^ sublimate (0.69 g) was extracted with, petroleum ether. Careful recrystallization from this solvent followed by resublimation at 50° C and 0.1 mm Kg yielded O.56 g (^6% of theory) of dimethylphosphonitrilic tetramer, M.P. 159-162** C. The infrared spectrum of this material was identical with that of dimethylphosphonitrilic tetramer reported in the literature.^ ^ The "P=N" stretching frequency occurs at 1220 cm" . A shoulder occurs at 1160 cm" indicating the presence of trimer. The concentration of trimer, however, was very low because no separation could be made by repeated fractional crystallization from petroleum ether. The residue from the sublimation and the petroleum ether extractions v;ere clear oils which were insoluble in pe 'leum ether and benzene. This material was soluble in water and its water solution gave a strong test for chloride ion with aqueous silver nitrate. The infrared spectrum of this substance has strong peaks in the regions associated with 0-H bonding and has P-CH^ peaks. Therefore, it was postulated that this oil was a product of partial hydrolysis of dimethyltrichlorophosphorane or of some chlorinecontaining intermediate formed in the early stages of the reaction. The product, [(GH;,)2PN], ^, was quite soluble in this oil and some loss occurred when the oil was discarded.

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115 Discussion The results of this study show that, in general, phosphonitrilic derivatives result from the reactions of diaminophosphonium salts with tri-, tetraand pentachlorophosphoranes . This, then, indicates another procedure in which diaminophosphonium salts" can be used to obtain a variety of phosphonitriles. As a direct result of this study, some interesting new derivatives were formed. For instance, the reaction of dimethyldiaminophosphonium chloride with PCln has produced the 'trimer," (CH^)pCl^P,I!T, in moderate yields. This material was characterized by elemental analysis, molecular weight determination and infrared analysis. Its infrared spectrum (Fig. 19) has a strong peak at 1420 cm" which may be attributed to C— H bending vibrations, and a doublet at about 1500 cm" which is attributed to P— CH^ bonding. In the region characteristic of "P=N" stretching, two peaks occur, one at 1220 cm" and the other at 1165 cm" and from 865 cm" to 960 cm" . Peaks in this region have been attributed to P— stretching and to methyl C-H vibrations as well as to "P=N" elongation and "P-N=P" ring vibrations. Not enough information is available yet for us to make definite assignments in these regions. Several strong peaks occur between 510 and 632 cm Daasch' ^ attributes peaks in this region to PGI2 vibrations and to phosphonitrilic ring vibrations.

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116 Considering the method of synthesis, this "trimer" probably has the structure, °k .ci or X^/%1 ,^ with both methyl groups on the same phosphorus. Such a derivative cannot be synthesized by substitution reactions starting with (PNCl2):z. The byproduct of this reaction was an air-sensitive, glassy material, which when pyrolyzed at 180-190° C in vacuum, yielded a glassy substance which seemed to be a cross-linked polymer derived from the grouping, [(CK^)2PN-Cl2PN]. The reaction of diethyldimainophosphonium chloride with PC1|produces low yields of a substance tentatively identified as the tetramer, 1(02^.^)2^^''^^ 2^^'^ 2' ^^® infrared spectrum of this material (Fig. 20) has C— H stretching and deformation peaks at 2960, 2920 and 2860 cm~ and at 1^50 and 1^00 cm" , respectively. A strong peak occurs at 1279 cm" which is usually associated with P-C bonding. Two peaks characteristic of the phosphonitrilic "P=N" stretching vibrations occur at 1200 cm" and at 11 50 cm" . A number of peaks occur in the region from 600 cm to 1030 cm" , Peaks in this region are often attributed to

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117 C-K vibrations of the ethyl groups and to various vibrations of the phosphonitrilic ring. Definite assignments are (97) difficult to make, however, the peak at 788 cm" can probably be attributed to ?-C asymmetric stretching, and the peak at 510 cm" can probably be attributed to P— CI bonds. Several peaks occur between ^00 and 565 cm" , but no definite assignments of these peaks can be made. The main product of this reaction was a dark, airsensitive oil. 3y pyrolysis at 200-220° C this substance was converted to a brown, glassy solid which was apparently unreactive in air. The analysis of this material indicates the formula, [(C2H^)2PN-Cl2PN] . The P:C1 ratio is 1:0.7 and this deviation from the theoretical ratio of 1:1 is attributed to cross-linking. The substance has the properties of a cross-linked polymer, being insolub!' e in all solvents tried and decomposing slowly in the range of 2^0250° C. The reaction of dimethyldiaminophosphonium chloride with methyltetrachlorophosphorane produces a white, airsensitive solid which, upon pyrolysis at about 180° C, gives a light-brown, glassy substance with an average molecular weight of 915. This material is still moisture sensitive. The analysis indicates the formula, [(CH;,)2PN* (CH;,)C1PN]^. The infrared spectrum of a thin film of this material (Fig. 21) has broad C— H stretching deformation peaks at 2900 cm"

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118 and at 1^00 cm"*, respectively. A broad peak occurs at 1305 cm" and can be attributed to P-CK^ bonds. The usual phospiionitrilic "P=:T" stretching peak occurs at about 1220 cm" and is quite broad. Several peaks occur in the region from 652 cm" to 980 cm" . No definite assignments can be made for peal:s in this region. A broad peak occurs at 455 cm" v;hich might be attributed to P— CI bonds. On the basis of the elemental analysis, molecular weight determination and infrared spectrum this material appears CH-7 GH-z CK:z CI to be a linear polymer of the unit, -r — P=N P=N-^ . The reaction of dimethyldiaminophosphonium chloride with dimethyl trichlorophosphorane produces 0.59 g (88% of theory) of crude [(CH,)2PN];, ^. This material was purified by fractional crystallization from petroleum ether and resublimation, and was identified by its melting point and by comparison of its infrared spectrum with published data. The product consisted chiefly of tetramer (K.P. 159-162° C) and attempts to separate the small amount of trimer present by careful fractional crystallization from petroleum ether failed. The presence of trimer was indicated by the infrared spectrum which shows a shoulder at 1150 cm" , the position of the characteristic "P=N" stretching band in the trimer. In predicting the course of these reactions, we had considered it possible that diaminophosphonium salts would

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119 react v/ith chloropiiosphoranes in a manner similar to the reaction of KH.Cl and PCli(see Chapter II). Thus, the first product in the reaction of dimethyldiaminophosphonium chloride with PClc, for example, might "be the ion pair, [(CH,)pP(M2)2J© an^ ^Clg©. Intramolecular condensation could occur through loss of HCl This product could then undergo intermolecular condensation to produce cyclic and linear derivatives 2(CH^)2P^ ~ ^ ^=^^ (CHj)2P— N=PClj =221^ H K ^M [CGHj)2?N*Cl2PN]2 HIT [ P N=P— N=^==?P N^=P. 5 2 \^ 3 n-1 \q^ H The cyclic derivatives so produced would be predicted to be tetrameric. The linear derivatives, having a number of accessible P-Cl bonds, might be predicted to be air-sensitive. In addition, cross-linking through cleavage of P-Cl bonds might also be predicted to take place -i.n a manner similar to the polymerization of [PNCI2] . A similar reaction path might also obtain for methyltetrachlorophosphorane and dimethyltrichlorophosphorane.

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120 The results of this study generally confirm the predictions which were made considering the reaction sequence postulated ahove. In the reaction of dimethyldiaminophosphonium chloride with dimethyltrichlorophosphorane the principal product was the tetramer, [(CH^)^?^]^. Traces of trimer which were detected might have resulted from self-condensation of the phosphonium salt, 2C(CH^)2P(NH2)2]Cl-> [(CHj)2p(NH2)-N=P(2ra2)(CHj)2]Cl + NH^Cl [(CH^)2P(NH2)-N=P(im2)(CHj)2]Cl + (CH^)2PClj — > [(GHj)2P^T]^ + 4 HCl . The reaction of diethyldiaminophosphonium chloride v;ith PCIalso produces a tetrameric species tentatively identified as I (02^^)2^'^ ''^^2^^'^ 2' ^^® structure of this material was not determined. Such a determination would be interesting and would perhaps provide additional information about the course of the reaction. A material assumed to be a linear polymer of the CH-, CH-, CH^ 01 unit, -E P=];T P=l!T^, was obtained from the reaction of dimethyldiaminophosphonium chloride with methyltetrachlorophosphorane. The average molecular weight was 915 giving n an average value of about 5 (or 10 P-N units). The properties of the material are consistent with this

PAGE 129

121 assiimption. In addition, materials which appear to be crosslinked polymers derived from the units, [ (CH;,)2PN'Cl2PN] and [(C2Hc)2PN.Cl2PN] are formed in the reactions of PCln with dimethyldiaminophosphonium chloride and diethyldiaminophosphonium chloride, respectively. The only product of this study which cannot be easily rationalized by the sequence postulated above is the"trimer," CCH^)2C1.P;,I^,, which results from the reaction of PGl^ with dimethyldiaminophosphonium chloride. The formation of this "trimer" implies the formation of the substances WH.2~^'^^i^^ HN=PC1, and C1,P=I^-PC1,, . The latter species could condense ^ ^ qwith dimethyldiaminophosphonium chloride giving the observed "trimer." The nitrogen atom in the intermediate, C1,P=N-PC1^, might come from the possible contaminant, NH^Cl, since this intermediate is known to form in the reaction of NH^Cl and PCln. It might also come from the diaminophosphonium salt by some complex mechanism which cannot be predicted. Only one reaction sequence has been considered here. Of course, other sequences might be postulated which could account for this product as well as the other products of the reaction. The 'trimer," (GH,)2Cl^P:zN:z, is an interesting derivative. Since, under the conditions of the reaction, migration of the methyl groups is aot expected, the structure

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122 is, ir 3 CI J I /CI 01^ %,./ ^Cl This derivative caimot be prepared by substitution reactions starting with [PI^Clplz because substitution in such derivatives occurs evenly, one chlorine on each phosphorus undergoing substitution before the second chlorine atom is substituted. Therefore, this is presently the only kno\>ni method of preparation of this derivative. Likewise, the derivative, [.{02^^) 2^'^* CI 2^'^'^ 2 cannot be synthesized by substitution starting v/ith [PiTClol^. The question of the structure of the tetramer, [(C2Hi-)2PN'Cl2PN]2> ^^ also an interesting one. The material could be either Cl^ "^Cl C2H^ "^^2^5 Thus, a complete structural investigation is necessary to fully characterize this compound. Although this study has resulted in the synthesis of some interesting phosphonitrilic derivatives, the experimental difficulties involved preclude its classification as a "convenient" method. However, a more thorough

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123 study of these reactions using different solvents and different mole ratios of reactants might further clarify the results obtained in this study and might reveal some advantages in using this method for phosphonitrilic synthesis. Summary The reaction of dimethyldiaminophosphonium chloride with PClc in refluxing benzene has produced the new phosphonitrilic 'trimer," (CH-,)2C1^P^IT^, in good yield. The byproduct of this reaction is an air-sensitive solid which, upon pyrolysis at about 180° C, yields a material tentatively identified as a cross-linked polymer derived from the unit, [(CH^)2PN-Cl2pN] . The reaction of diethyldiaminophosphonium chloride with PClc in refluxing benzene has produced the tetramer, [(CpHc-)2PN«ClpPN]2, in low yield. The principal product in this reaction is an air-sensitive, oily material which gives an insoluble glass when pyrolyzed at about 200° C. This glass has been tentatively identified as a cross-linked polymer derived from the unit, [(C2Hc)2PI^*Cl2pN] . The reaction of dimethyldiaminophosphonium chloride with methyltetrachlorophosphorane in refluxing benzene produces a white solid which is air-sensitive. Pyrolysis of this solid at 180° C produces an air-sensitive glass

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12^ which. v;as tentatively identified as a linear polymer of the unit, [(CH2)p?F'(CE;,)ClPN]. The average number of units per chain, as indicated by molecular weight determination, is about 5. This material is produced in good yield. The reaction of dimethyldiaminophosphonium chloride with dimethyl trichlorophosphorane has produced principally dimethylphosphonitrilic tetramer in good yield. All products synthesized in this study v;ere characterized by melting point determination, elemental analysis, molecular v/eight determination (except for insoluble polymers) and infrared analysis. The results are discussed in terms of a postulated reaction sequence.

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CHAPTER VI GENERAL CONCLUSIONS AND STOIPIARY In general, this study has shovm that (1) diaminoand criaminophosphonium chlorides can he conveniently synthesized by the chloramination-ammonolysis of substituted diphosphines and cyclotetraphosphines ; (2) diaminophosphonium chlorides are phosphonitrilic precursors giving phosphonitrilic derivatives in good yield by pyrolytic condensation; (5) under certain conditions highly polymeric, linear, dimethylphosphonitrile can be synthesized in good yield from dimethyldiaminophosphonium chloride; and (^) diaminophosphonium salts undergo condensation reactions with PClc and substituted tetraand trichlorophosphoranes to give phosphonitrilic derivatives. In particular, it has been shown that chloramination-ammonolysis of tetramethyldiphosphine and tetraethyldiphosphine produces the corresponding diaminophosphonium chlorides in good yield. This method is presently the most convenient one known for the production of these substances. The chloramination-ammonolysis of tetraethyldiphosphine also produces a trace amount of diethylphosphonitrilic trimer. 125

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126 Chloramination-a-inonolysis of tetrapiienyldiphosphine produces the new compound, diptienyldiaminophosphonium chloride and its first condensation product, [(C E^)2p(iird^)-i:^=?(il\E2)(C^E^)^:\Cl. When carried out at room temperature in benzene the yield of diphenyldiaminophosphonium chloride is lov;. Further study of this reaction might reveal conditions under which the yield of this diaminophosphonium salt could be optimized. The chloramination-ammonolysis of tetraphenylcyclotetraphosphine has produced the nev; compound, phenyl triaminophosphonium chloride, and a substance tentatively identified as the linear polymer, 6 5^ / 2 o 5. / 2 CI— r P 'i^—i-E v?==I\H . Even though this reaction was carried out at room temperature, the yield of the triaminophosphonium salt was sometimes as high as 25 per cent of theory. Further study might reveal conditions under which jhe yield of this salt might be even higher. The study of the pyrolytic condensation of diaminophosphonium chlorides has demonstrated thoroughly the value of the reaction sequence postulated earlier,^ ' and has shov/n that these salts are indeed precursors of phosphonitrilic poljrmers. Thus, dimethyldiaminophosphonium chloride undergoes pyrolytic condensation to produce excellent yields cf dimethylphosphonitrilic trimer and tetramer. Diethyldiaminophosphonium chloride undergoes condensation in steps

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127 giving tlie first condensation product, [(C2H^)2?(^^2^~*''^^^^^^2^'^^2-^5^2^^"^' ^^ diethylphosphonitrilic trimer. The intermediate, [(C2H^)2?(^^2^~^=^^^2^ ^^2^5^2^^-^ undergoes pyrolytic condensation to give excellent yields of diethylpiiosphonitrilic trisier and tetranier. Trie tetracier is the predominant product of this reaction. The pyrolytic condensation of di-n-butyldiaminophosphonium chloride produces the nev; compound, [(in-C^Ef.')^^^'^^ ^^ excellent yield. One of the most important results of this work was the discovery of the conditions under which dimethyldiaminophosphonium chloride could he polymerized to give a highly polymeric, linear dimethylphosphonitrile. Yields of crude polymer as high as 50 per cent of theory v;ere obtained by varying the concentration of ammonium chloride in the pyrolysis mixture. This material contains polymers of the unit, [(CH^)2PN] with molecular weights which average from 3500 to 12,500, indicating molecules in which the average number of units varied from 50 to 150. The discovery of polymeric dimethylphosphonitrile leads one to speculate about the possibility of developing a useful, unreactive, thermally stable phosphonitrilic polymer system. The dimethylphosphonitrilic polymer synthesized in this study has been demonstrated to be unreactive ^0 moist air, and has been shown to have potential uses in tne fabrication of films. Hov;ever, the material is

PAGE 136

128 thermally degraded to cyclic derivatives, [(CK,)2PN]^ ^, upon heating above 300° C. The answer to this problem is to build into the polymer molecules end-stopping groups and branching or cross-linking groups to lock the linear chains in position and to prevent cyclization. An analogous situation occurs in the isoelectronic dimethyl siloxane derivatives which have the unit, [(CH-,)pSi-0 ] (93) Cyclic derivatives and not linear polymers are favored at high temperatures unless some end-stopping groups, [(CH;z)^Si-0] , and branching groups, I (GH^)Si-O , are incorporated in the high polymer. This study has shown that dimethyldiaminophosphonium chloride is the staj?ting material for the chainCH-2 CH-, <^ / 5 making units, [— N— P-N— ] , Ve have also indicated a method of of synthesizing the starting materials for the branching N , namely, the chloramination-ammonolysis of unios, HP-NI N cyclopolyphosphines , (RP)^. NH2CI EH 3 J x[RP(Ml2)5]Cl And the synthetic procedure for compounds v/hich lead to end groups, [R^P— N— ] , is the well-known^ "^^ chloramination of tertiary phosphines. The basic structural units for the

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129 ph-osph-onitrilic polyner system are therefore available. We feel that tlie syrLthesis of polymers utilizing these units would make a very interesting study for further v;oric in this area. The reactions of dimethyldiaminophosphonium chloride and diethyldiaminophosphonium chloride with PClc, methyltetrachlorophosphorane and dimethyl trichlorophosphorane also produce phosphonitrilic derivatives. Dimethyldiaminophosphonium chloride reacts with PClcto produce good yields of the "trimer," (CH^)2Cl^PvN^. A second product of this reaction is an air-sensitive oil which can be pyrolyzed to yield a material that appears to be a cross-linlced polymer derived from [(CH^)2PN*Cl2PN] . Similarly, diethyldiaminophosphonium chloride reacts with PClc to form the tetramer, [(CpHt-)pPN'ClpPlT]p, and an air-sensitive substance which can be pyrolyzed to yield a material that appears to be a cross-linked polymer derived from [(C2H[-)2PN*Gl2PN] . The reaction of dimethyldiaminophosphonium chloride with methyltetrachlorophosphorane produces an extremely air-sensitive material which was pyrolyzed to yield a material that appears to be a low-molecular-weight linear polymer of the unit, [(CH^)2?NCCE^)C1P:Tj . The reaction of dimethyldiaminophosphonium chloride with dimethyl trichlorophosphorane produces, predominantly, dimethylphosphonitrilic tetramer.

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130 The reactions studied in Chapter V are somewhat analogous to the so-called ring-closure reactions observed with [(CgH^)2P(mi2)-N=?Cim2)(CgH^)2]Cl and PCI3, HPCl^ and R2PC1,.^-^' ^ Hov;ever, the reactions studied here differ by the important distinction that linear and cross-linked polymers are formed, sometimes in high yield.

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BIBLIOGRAPHY 1. H. H. Sisler, H. S. Ahuja and N. L. Smith, Inorg. Chem. , 1, 8^(196^). 2. I. I. Bezman and J. H. Smally, Cliem. and Ind. , 859 (I960). 5. G. D. Schmulbach. and C. Derderian, J. Inorg. Nucl. Chem., 25, 1595(1953). ^. D. L. Herring and C. M. Douglas, Inorg. Chem., 5, ^28 (196^). 5. S. E. Frazier, Master's Thesis, University of Florida, December, 1965. 6. H. H. Sisler and 3. E. Frazier, Inorg. Chem., ff, 120^(1965). 7. J. Liebig, Ann., 11, 159(185^). 8. J. H. Gladstone and J. K. Holmes, J. Chem. Soc, 17 , 225(1364). 9. H. N. Stokes, Am. Chem. J., 17, 275(1895); 18» ^29 (1896); 19, 782(1897); 20, 7^0(1898). 10. R. A. Shaw, B. W. Fitzsimmons and B. C. Smith, Chem. Rev., 3, 2^7(1962). 11. IT. L. Paddock, Quart. Rev., 18, 168(1964). 12. C. P. Haber, Inorganic Polymers , Chem. Soc . Special Publ. , 15, The Chemical Society (London7T~115(l961) . 13. L. G. Lund, et al ., J. Chem. Soc, 25^2(1960). 14. D. P. Craig, J. Chem. Soc, 997(1959). 15. M. J. S. Dewar, E. C. A. Lucken and M. A. I-Thitehead, J. Chem. Soc, 2423(1960). 16. D. P. Craig and N. L. Paddock, J. Chem. Soc, 4118(1962) 131

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152 17. D. ?. Craig, Cheni. and Ind. , 3(1958). 18. B. Lakatos, et al . , Naturwiss., 21, 495(1952). 19. D. Fealcins, V. A. Last, N. Neemuchvmla and R. A. Shaw, J. Ctieni. Soc, 2804(1965). 20. D. Feakins, W. A. Last and H. A. Shaw, J. Chem. Soc, 4464(1964). 21. L. Pauling, The i-Tature of the Chemical Bond , Third Edition, Cornell University Press, I960. 22. 3. Constantinides, Proc. Chem. Soc, 290(1964). 25. F. Seel and J. Langer, Z. anorg. Chem., 295, 516(1958). 24. L. W. Daasch, J. Am. Chem. Soc, 76, 5^05(195^). 25. A. J. Bilbo, Z. Naturf orsch. , 15b, 550(1960). 26. H. T. Searle, Proc Chem. Soc, 7(1959). 27. L. ?. Audrieth and D. B. Sowerby, Chem. and Ind., 748(1959). 28. K. John and T. Moeller, J. Am. Chem. Soc, 82, 2647 (I960). 29. N. E. Bean and S. A. Shaw, Chem. and Ind., 1189(1960). 50. P. G-. Rice, et al . , J. Inorg. Nucl. Chem., 5, 190(1958). 51. 0. Schmitz-Dumont and H. Kulkens, Z. anorg. Chem., 258, 189(1958). 52. A. C. Chapman, et al . , J. Chem. Soc, 1768(1961). 55. A. C. Chapman, et al . , J. Chem. Soc, 5608(1960). 54. R. Ratz and Ch. Grundmann, J. Inorg. Nucl. Chem., 16, 60(1960). 55. T. Hoeller, K. John and E. Tsang, Chem. and Ind., 547(1961). 55. R. J. A. Otto and L. E. Audrieth, J. Am. Chem. Soc, 80, 5894(1958).

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133 37. G. Tesi, et al . , J. Am. Chem. Soc, 82, 528(1960). 38. G. Grundmaiin and R. Ratz, Z. Naturf orsch.. , 10b, 116(1955). 59. R. Ratz and Vi. Hess, Chem. Ber. , a^, 889(1951). ^0. B. Dishon, J. Am. Chem. Soc, 71, 2251(19^9). ^1. S. G. Kokalis, et al . , J. Inorg. Nucl. Chem., 19, 191(1961). ^2. S. K. Ray, R. A. Shaw, B. C. Smith, J. Chem. Soc, 3236(1963). 43. R. J. A. Otto and L. F. Audrieth, J. Am. Chem. Soc, 80, 3575(1958). 44. H. Bode and H. Bach, Chem. Ber., 753, 215(1942). 45. R. A. Shaw and F. B. G. Wells, Chem. and Ind., 1189(1960). 46. H. Bode and R. Thamer, Chem. Ber., 76B, 121(1943). 47. R. A. Shaw and M. Biddlestone, Chem. Comm. , 205(1965). 48. M. Becke-Goehring and K. John, Angew. Chem. , 70, 657(1958). 49. G. Tesi and P. J. Slota, Jr., Proc. Chem. Soc, 404(1960). 50. M. Becke-Goehring and G. Koch, Chem. Ber., 92, 1188(1959). 51. N. L. Paddock and H. T. Searle, Adv . Inorg . Chem. Radiochem. , Academic Press, New lork, Vol. I, p. 552, 1959. 52. H. R. Allcock and R. J. Best, Can. J. Chem., 42, 447(1964). 53. F. Seel and J. Langer, Angew. Chem., 68, 461(1956). 54. A. 3. Lu.-^-, J. Chem. Ed., 37, 482(1960). 55. D. L. Herring, Chem. and Ind., 717(1960).

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15^ 56. G. Tesi, G. ?. Kaber and C. Vi. Douglas, Proc. Chem. Soc, 219(1960). 57. K. L. Paciorek, Inorg. Chem., 2» 96(196^). 53. I'l. yinyall and H. H. Sisler, Inorg. Chen., ^, 655(1965). 59. li. 3. Cohen, et_al. , U. S. Dent. Comni. Office Tech. Serv. , ?H Repz, 161,383(1960). 60. y. h. Groeneveld, et; a l. , J. Inorg, Nucl. Chem., 8. 2^5(1953). 61. K. Goehring and J. Heinke, Z. anorg. Chem., 278, 53(1955). 62. C. ?. Lui and R. L. 3vans, U. S. Patent ,}^3,169,933 (Peb. 16, 1965). 63. H. A. Shav; and C. Stratton, J. Chem. Soc, 500'4-(1962) . 6-+. C. P. Haher, D. L. Herring and S. A. Lav;ton, J. Am. Chem. 3oc., £0, 2116(1958). 65. 1. J. Mao, R. D. Dresdner and J. A. Young, J. Am. Chem. Soc, SI, 1020(1959). 66. G. 'Tesi and C. X. Douglas, J. Am. Chem. Soc, S'4-, 5^9(1962). — 67. I. T. C-ilson and H. K. Sisler, Inorg. Chem., ^, 275(1965). 68. 11. H. Sisler, P. T. Neth, R. 3. Drago and D. Young, J. Am. Chem. Soc, 76, 5906(195^). 69. P. Paschig, Chem. 3er. , fi^, ^586(1907). 70. P. Mattair and K. li. Sisler, J. Am. Chem. Soc , 73 > 1619(1951). 71. G. I'l. Omietanski, et al . , J. Am. Chem. Soc, 73, 587^(1956). 72. G. M. Omietanski and H. H. Sisler, J. Am. Chem. Soc, 73, 1211(1956). 73. H. H. Sisler, et al . , J. Am. Chem. Soc, 81, 2982(1959).

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135 7'4-. •. A. Hart, Studies of the Chloramination of Aminophosphine Deriva-uives . Ph.D. Dissertation, University of Florida, August, 1963. 75. V. A. Hart and H. H. Sisler, Inorg. Chem. , 3, 617(195^). 76. D. ?. Clemens and H. H. Sisler, Inorg, Chem. , 4, 1222(1965). 77. K. Issleib and W. Seidel, Chem. Ber. , 92, 2681(1959). 78. W. Zuchen and H. Buchwald, Chem. Ber. , 9i, 2871(1958); 91, 2296(1958). 79. H. H. Sisler and N. L. Smith, J. Org. Chem., 26, ^753(1961). 80. A. B. Burg, J. Inorg. Nucl. Chem., 11, 258(1959). 81. K. Issleib and A. Tzschach, Chem. Ber., 92, 1397(1959). 82. H. Hoffmann, S. Grunewald and L. Horner, Chem. Ber., 95, 861(1960). 83. A. B. Burg, J. Am. Chem. Soc, 83, 2226(1961). 8^. L. Maier, J. Inorg. Nucl. Chem., 2A, 275(1962). 85. H. Mebergall and B. Langenfeld, Chem. Ber., 90, 1657(1957). 86. H. Reinhart, D. Bianchi and D. Moelle, Chem. Ber., 90 , 1657(1957). 87. S. E. Frazier, R. ?. Nielsen and H. H. Sisler, Inorg, Chem., 3, 292(196^). 88. J. McKechnie, D. S. Payne and W. Sim, J. Chem. Soc, 3500(1985). 89. W. A. Anderson, M. Epstein and F. S. Seichter, J. Am. Chem. Soc, 85, 2^62(1963). 90. R. L. Amster, V. A. Anderson and N. B. Colthup, Can. J. Chem., fi^, 2577(196^). 91. I. N. Zhmurova, I. Yu. Voitsekhovskarya and A. V. Kirsonov, Zhur. Obshchei Khim. , 29, 2083(1959); C.A. 5^:8681h.

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136 92. A. Michaelis, Ann., 295, 195(1895); 29^, 1(1396). 93. E. Steger, Chem. Ber. , 9^, 266(1961). 9^. V. Vi. Plets, Dissertation, Kazan, 1958; G. M. Kosolapoff , Org;anot)hosphoru5 Compounds , John Wiley and Sons, Inc., DTev; York, 1950. 95. Rip G. Hice, Private Communication. 96. I. P. Komkov, etal . , Z. Obshciiei Khim. , 52, 501(1962); C.A. 57:166^9b. ~ 97. G. B. Deacon, R. A. Jones and P. E. Rogasch, Austral. J. Chem., 16, 560(1965). 98. E. G. Rochow, An Introduction to the Chemistry of the Silicones, Second Edition, John Wiley and Sons, Inc., New York, 1951.

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BIOGHAPHICAL SKETCH StepiLen Earl Frazier was "born October 21, 1959, at Spencer, VJest Virginia. In June, 1957, lie was graduated from Tarpon Springs High. School in Tarpon Springs, Florida, Eroa September, 1958, until June, 1961, he worked as a laboratory assistant in the Department of Chemistry at Florida Southern College. He received the degree of Bachelor of Science from Florida Southern College in June, 1961. Upon graduation he enrolled in the Graduate School of the University of Florida. He received the degree of Master of Science in December, 1963. He worked as a teaching assistant until January, 1962, and as a research assistant in the Department of Chemistry while pursuing his graduate degrees. Mr. Frazier is a member of the American Chemical Society, Omicron Delta Kappa, Gamma Sigma Epsilon and \^^ho's Who .\mong Students in American Universities and Colleges (1960-1961). 137

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This dissertation was prepared under the direction of the chairman of the candidate's supervisory committee and has been approved by all members of that committee. It was submitted to the Dean of the College of Arts and Sciences and to the Graduate Council, and was approved as partial fulfillment of the requirements for the degree of Doctor of Philosophy. December 18, 1965 Dean, ColMge' of' Arts and Sciences Supervisory Committee: ^"^hai airmj ^^ ^S^M^.v^'p-A^ t^ /:-tt Dean, Graduate School ' ^ ^ >iJ^AfyJuU^ u^^-^^:

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