Boron derivatives of polyamines: borane adducts and cyclic cations

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Boron derivatives of polyamines: borane adducts and cyclic cations
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Manziek, Larry, 1946-
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Thesis:
Thesis--University of Florida.
Bibliography:
Includes bibliographical references (leaves 136-138).
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by Larry Manziek.
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Typescript.
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Vita.

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University of Florida
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Boron Derivatives of Polyamines:
Borane Adducts and Cyclic Cations









By

LARRY MANZIEK


A DISSERTATION PRESENTED TO THE GRADUATE COUNCIL OF'
THE UNIVERSITY OF FLORIDA IN PATI.:L
FULFILLMENT OF THE REQUIREMENTS FOR THE DEGF-E OF
DOCTOR OF PHILOSOPHY













UN DIVERSITY OF FLORIDA
1976













.ACKNOWT; jl DGn' I E TS


The author wishes to presss his deepest appreciation

to his Chairman, Dr. George E. Ryschkewitsch, whose guid-

ance, enthusiasm, encouragement, and patience during the

execution of this research program were of inestimable

value.. Dr. Ryschkewitsch was not only research supervisor,

but friend, whose lending ear was always available.

The author wishes to express his gratitude to the

members of his Supervisory Committee for the aid and gacd-

ance they have given, both in and out of the classroom.

He is deeply indebted to his fellow graduate students and

post-doctoral fellows of his research group, whose advice

and direction were a constant source of encouragement.

The author is very thankful to Dr. '.allace Brey and

his associates for obtaining the B11 nuclear magnetic

resonance spectra reported in this study.

Special thanks are due Ms. Ella Levins for the typ-

ing of the first draft of this dissertation and to

Ms. Eileen- Dit.tmar for diligence, conscientiousness, and

sped in the final typing of this dissertation.

The author wishes also to acknowledge

Dr. Ralph K. Birdwhistell, Chairman, Department of Chem-

istry, University of West Ilorida, whose advice aned

.support throughout his undergraduate and gjr-iduate stzidies







were of inestimable value.

Finally, the author would like to express his deepest

thanks to his parents for their support and encouragement

throughout the course of his college education.


iii














TABLE OF CONTENTS


ACKNOWLEDGMENTS ....... ......... ...................

LIST OF TABLES .....................................

LIST OF FIGURES ....................................

ABSTRACT ...... ... .... ......... ......... ..... .......

Chapter

I. INTRODUCTION ..............................

II. MATERIALS AND INSTRUMENTATION .............

III. SYNTHESIS OF 2,2'-DIPYRIDYLMETHANE
AND DERIVATIVES ...........................

IV. SYNTHESIS OF POLYAMINE-BORANES ............

V. SYNTHESIS OF CYCLIC BORONIUM
CATIONS DERIVED FROM TERTIARY
POLYAMINE-BORANES .........................

Cyclic Cations Derived from
Reactions of Polyamine-Boranes
with Iodine or Trimethylamine-
lodoborane ..............................

Synthesis of Cyclic Boronium
Cations by Methods other than
Reactions of Polyamine-Boranes
with Iodine or Trimethylamine-
lodoborane ..... ........................

Reactions and Derivatives of
2,2'-Dipyridylmethanedihydroboron
(1+) Salts ..............................

VI. PHYSICAL MEASUREMENTS .....................

Acid Base Dissociation Constant
Determination Using Electronic Spectra ..

Infrared Spectra ........................

Nuclear Magnetic Resonance Spectra ......


ii

vi

vii

viii



1

12


14

25



40




40





62



66

79


79

81

82







VII. DISCUSSION .................................. 96

2,2'-Dipyridylmethane and Derivatives ..... 96

Ammonium (1+) Salts .................... 100

2,2',2"-Tripyridylmethane ................ 101

Polyamine-Boranes ........................ 102

Cyclic Borcnium Cations ................... 105

Boronium Cations Containing
Amine-Boranes ................... ........ 113

2,2'-Dipyridylmethanedihydroboron (1+),
and Its Reactions ................. ...... 121

Reaction of 2,2'-Dipyridylmethane
with Trimethylamine-Iodoborane ............ 126

Nuclear Magnetic Resonance Correlations
of 2,2'-Dipyridylmethane and Derivatives .. 128

Critique of Reported Literature
Related to This Study ..................... 130

BIBLIOGRAPHY ....................... .. .. ...... .... 136

BIOGRAPHICAL SNETC ........................ ........... 139











LIST OF TABLES


Table

I. Yields, Melting, and Boiling Points
of 2,2'-Dipyridylmethane and Derivatives .... 24

II. Yields and Melting Points of
Polyamine-Boranes ......................... 38

III. Yields and Melting Points of
Cations and Derivatives ................... 76

IV. Acid Base Equilibrium Data of
2,2'-Dipyridylmethanedihydroboron
(1+) Chloride ............................... 84

V. Proton NMR Data of 2,2'-Dipyridyl-
methane and Derivatives ................. 85

VI. Proton NMR Data of Polyamine-Boranes ........ 86

VII. Proton NMR Data of Boron Cations
and Anhydro Bases ........................ 90

VIII. 11B Data ................................... 95














LIST OF FIGURES


Figure

I. Electronic Spectra of the Anhydro
Base of 2,2'-Dipyridylmethanedi-
hydroboron (1+) Chloride .................. 83


vii












Abstract of Dissertation Presented to the Graduate Council
of the University of Florida in Partial Fulfillment of
the Requirements for the Degree of Doctor of Philosophy



Boron Derivatives of Polyamines:
Borane Adducts and Cyclic Cations

By

Larry Manziek

December, 1976

Chairman: George E. Ryschkewitsch
Major Department: Chemistry

Two areas of polyamine chemistry were investigated.

The first deals with a new synthetic method for the synthe-

sis of 2,2'-dipyridylmethane and various derivatives. The

second describes a new synthetic method, employing poly-

amines, for the synthesis of cyclic boronium cations, cyclic

boronium cations containing an amine-borane group,and re-

actions and derivatives of the cyclic boronium cation de-

rived from 2,2'-dipyridylmethane.

The diamines 2,2'-dipyridylmethanol, 2,2'-dipyridyi-

chloromethane, and 2,2'-dipyridylmethane were obtained from

the three step reaction of 2,2'-dipyridylketone with aqueous

sodium borohydride, tri-n-octylphosphine and carbon tetra-

chloride, and powdered zinc in aqueous acid, respectively.

Reaction of 2,2'-dipyridylmethane and 2,2'-dipyridylchloro-

methane with aqueous ammonium hexafluorophosphate provided

ammonium (1-) salts. The triamine 2,2',2"-tripyriidylmethane







was obtained from the reaction of 2,2'-dipyridylmethane with

phenyl lithium and 2-bromopyridine.

Reaction of polyamine-boranes of tertiary aliphatic,

tertiary-aromatic, or mixed (aromatic, aliphatic) polyamines

with iodine or trimethylamine-iodoborane results in high

yields of cyclic boronium cations. The reaction is highly

selective for cyclic cation formation, with no linear cation

formation observed. The general utility of this method has

been demonstrated with sixteen polyamine-boranes containing

various combinations of aliphatic and aromatic amines.

The polyamine-boranes investigated showed a definite

trend in reactivity. The rate of reaction was found to be

dependent on the type of amine, and the ring size of the

resulting cation. Reactivity followed the general orders:

aromatic polyamine-boranes > mixed (aromatic, aliphatic)>

polyamine-boranes > aliphatic polyamine-boranos, and five--

membered rings > six-membered rings > seven-membered rings.

The ordcr of reactivity for various ring sizes provided a

high degree of selectivity in cation formation.

When tris(boranes), derived from either symmetrical or

unsyp'L eI;trical tertiary triamines, were reacted with iodine

or trimethylamine-iodoborane, selective ring closure was

observed. The cations obtained represent a new class of

boronium cation, in which an amine-borane group (N-BI13) is

also present in the molecule.

The cyclic boronium cation derived from 2,2'-dipyridyl-

methane exhibits an enhanced reactivity of the bridging






methylene hydrogens toward proton loss. The enhanced re-

activity is attributed to the inductive effect of the boryl

(BH +) group. Abstraction of a proton from the cation
(Ka = 12.13) resulted in the isolation of a stable zwitterion

whose reactivity toward electrophilic reagents provided a

means by which additional functionality could be incorporated

into the amine under mild conditions.

All new compounds were satisfactorily characterized by

their elemental analysis, proton nmr spectrum, and infrared

spectrum.












CHAPTER I

INTRODUCTION


The chemistry of boron-nitrogen compounds, especially

that of boron cations derived from tertiary amines, has

grown rapidly over the past decade.1 Interest in these

cations, however, has concentrated mainly around reactions

of the boron center and only a meager amount of work has

been described concerning reactions of the coordinated

amines."

Miller and Muetterties have described the formation of

a charge-compensated carbanion (I) by the abstraction of

a proton from bis(trimethylanine)boronium chloride with butyl-

lithium. 2

(M-N)2BH2 CI C4H Li-- MeMNBHFNM aH2 Li
I


This then rearranges by either an intra- or inter-molecular

process to form (trimethylamine-borylmethyl) dimethylamine

(II).3

MeNBH2CH NMe2
II


Similarly, Abate has reported that the cyclic boronium

cation derived from 2,2'-dipyridylamine undergoes a proton

abstraction under mildly basic conditions to produce a

zwitterion.'









HN

H2 R2


More recently, Gragg has investigated the reduction

of bis(trimethylamine)boronium iodide with sodium potassium

alloy to produce a new boron heterocycle.

yle2 H2

(MeN BH2I Na-K llo e2

H2


None of these reactions occur with the free amine under

similar conditions. Thus, it is evident that the presence

of the boryl group (BH2+) enhances the reactivity of each

system. It appears as if the change in chemical reactivity

in the above examples correlates well with the chemistry of

quaternary ammonium salts and amine adducts of Lewis acids.

The enhanced reactivities toward proton abstraction and

nucleophilic substitutions of quaternary ammonium salts are

well described in the literature. Such classical reactions

as the Hofmann degradation, Stevens rearrangement, and ylid

formation from quaternary ammonium salts are representative

examples of the enhanced reactivity toward proton abstraction.

Amine adducts such as pyridine N-oxides and metal complexes

have also been shown to exhibit similar enhanced reactivities.

The nucleophilic substitution reactions of the pyridine

system have been studied in the most detail. As the ability

of the pyridine ring to undergo electrophilic attack is de-

creased, nucleophilic attack becomes easier. For example, the









conversion of pyridine to its proton salt increases the

rate of nucleophilic substitution.6

The greater reactivity of 1-alkyl and 1-arylpyridinium

salts toward nucleophilic reagents is manifested in a

variety of reactions which are not possible with the free

bases. One reaction that has received considerable attention

is that of the formation of anhydro bases. When a quaternary

pyridine bears an alkyl group in the 2 or 4 position from

which a proton may be lost, the quaternary hydroxide is in

equilibrium with a non-ionic base, which is formed by the

removal of a proton.



CH2R =CHR
Me 'fe
R = alkyl or aryl

Decker pointed out the structural features necessary for

this conversion and some of the properties of such systems.7

One such property is their behavior as carbanionic nucleo-

philes due to the more appreciable negative charge on the

carbon atom, resulting from contribution of the following

resonance structure:



CH2
Me


Comparison of quaternary ammonium salts to boronium

salts suggest that the boryl group (BH2+) would produce

similar enhanced reactivity, and hence, should be considered







as an activating group for proton abstraction, and nucleo-

philic reactions on coordinated amines. One could also

postulate that an increase in reactivity would be observed

in the case of amine-borane adducts. The magnitude of this

increase should not be as great as in the case of the boryl

group (BH2 ), but should be considered since coordination

of the borane to nitrogen would in effect increase the elec-

tronegativity of the nitrogen atom, thus enhancing the

electrophilic character of the coordinated amine.

From the previously described chemistry of anhydro

bases, selection of a model system to investigate the en-

hancement of the acidity of carbon-hydrogen bonds in boronium

cations was undertaken.

The model chosen was 2,2'-dipyridylmethane (III).






III

In this molecule, the acidity of the bridging methylene

protons would be enhanced by the inductive effects of the

nitrogen atoms and resonance delocalization of the electron

pair in its conjugate base. Proton abstraction from the

bridging methylene group does occur in the free amine.

However, strong bases such as phenyllithium are required.

Bayer has demonstrated that zinc and cobalt(II)

complexes of 2,2'-dipyridylmethane show enhanced reactivity

toward proton loss.8 Guckel has also shown that when

2,2'-dipyridyimethane is allowed to react with diiodomethane,







the resulting chelated quaternary ammonium (2+) salt under-

goes reactions with weak bases, such as pyridine, to pro-

duce an intensely colored (1+) salt.9



,2 2
2iII 2f2 I 2



The intense color is attributed to resonance delocalization

of the electron pair providing for more extended conjugation

in the molecule.

The synthesis of a cyclic boronium cation, derived from

2,2'-dipyridylmethane, should produce enhanced acidity of the

bridging methylene protons and the resonance delocalization

of the electron pair, resulting from proton abstraction,

should also provide sufficient stability for the isolation

of an anhydro base (IV) derived from the boron cation.






42 '12
Iv
The reaction chemistry of this base (IV) toward electro-

philic reagents would be of interest in light of the nucleo-

philic properties exhibited by other anhydro bases. The

nucleophilic character would depend considerably on the

extent of resonance delocalization of the electron pair.

However, this reactivity, if present, would allow the

incorporation of additional functionality into the boron cation

which otherwise might not be possible. Thus, it might be








expected that the reaction of the anydro base (IV), derived

from the cyclic boronium cation of 2,2'-dipyridylmethane (III),

with methyl iodide, would yield a methyl derivative (V).

Me



H2 H2
V

The isolation of a trigonal boron heteroaromatic system

is also of interest.








No compounds of this type have yet been isolated, but evidence

for their existence in solution has been reported.410

Recently Abate, in an unsuccessful attem-pt to isolate such

a cation, reported the abstraction of a hydride ion from the

anhydro base (VI), derived from the cyclic boronium cation

of 2,2'-dipyridylamine, employing triphenylmethyl perchlorate.4




I'Y +t"c'o4, Icio4
H2
VI
Although this system is quite similar to that under discussion,

the replacement of the bridging nitrogen atom with a less

electronegative carbon atom might provide for increased de-

localization of the electron pair, hence, greater stability

of the cation. Therefore, the abstraction of a hydride ion







from the anhydro base of a 2,2'-dipyridylmethane boronium

cation (IV), employing triphenylmethyl perchlorate, might

lead to an isolable product.





H2


This conjugated molecule, which is homomorphic to anthracene,

contains a Huckel number of electrons (4n+2) representative

of an aromatic system.

During this work, the synthesis of the cyclic boronium

cation of 2,2'-dipyridylmethane appeared in the literature.11

Its physical properties did not support the previous proposals

for its reactivity, nor did the initial findings in this

laboratory correlate with those reported. This suggested

that further investigations were necessary in order to better

understand the system.

The diamine 2,2'-dipyridylmethane (III) was first syn-

thesized in low yield by the reaction of acetonitrile, sodium

amide, and 2-bromopyridine, to give dipyridyl-(2)-acetonitrile

(VII), which was hydrolyzed and decarboxylated to obtain

2,2'-dipyridylmethane.12


CN
MeCN NINH2 I

0Br VII III








Subsequently, it has been prepared by the reaction of 2-picolyl

lithium or sodium (derived from the reaction of 2-methyl-

pyridine with either phenyllithium or sodium amide) with

either pyridine or 2-bromopyridine.13-15



N -,


Br


A multistep synthesis, starting with the preparation

of 2,2'-dipyridylmethanol (VIII), has also been described.16



0 SOC12










Preliminary investigations of these reported methods of

synthesis suggested that they would not be useful for this

study since the yields were low and the products were diffi-

cult to purify. Therefore, the investigation of a possible

new synthetic route was undertaken.

The commercially available compound 2,2'-dipyridylketone

could represent a convenient starting point for the synthesis

of 2,2'-dipyridylmethane. It has been reported that attempts

to reduce the carbonyl directly to the alkane by classical

methods were unsuccessful. This is surprising, since








benzophenone, which is homomorphic with 2,2'-dipyridylketone,

undergoes reduction easily, yielding diphenylmethane.

It should be possible, however, to reduce the ketone to

the alcohol and then proceed through a reaction pathway

similar to that previously described.16

The synthetic methods employed for the synthesis of

boron cations from tertiary amines are well described, and

allow numerous variations providing considerable flexibility

for their synthesis.1,17 Preliminary investigations of

some of the more general methods failed to produce the

desired cyclic cation from 2,2'-dipyridylmethane. This was

quite surprising, since the synthesis of the analogous boronium

cation of 2,2'-dipyridylamine proceeded successfully by

several of these methods. The failure of 2,2'-dipyridylmethane

to behave as a typical diamine initiated the investigation for

a new method of synthesis for the cyclic cation.

Concurrently with this work, McMaster was investigating

the reaction of amine-boranes with amine-iodoboranes and

observed the following:18 When 4-methylpyridine-borane is

allowed to react with 4-methylpyridine-iodoborane, in benzene,

the products are bis-4-methylpyridine-boroniumiodide and

diborane.

ye Myle



BH 3 aB2







Comparison of the diamine 2,2'-dipyridylmethane with

the starting materials and cation produced above, suggest

that the two systems are structurally quite similar and

that suitable conditions might exist for an intra-molecular

reaction to produce the desired cation, assuming that the

borane and iodoborane entities can be incorporated into

the diamine.




B.'S BHr2T H2


Incorporation of the borane and iodoborane entities

might be accomplished by the reaction of the bis(borane)

of the diamine with a stoichiometric amount of iodine

necessary to iodonate only one of the borane groups.



SH2
BH3 BH BH B


This system would then be expected to produce the cyclic

cation in a reaction analogous to that of the 4-methylpyridine

system. Extension of this reaction sequence to other bis

(boranes) might also provide for a new general synthetic

procedure for the synthesis of cyclic boronium cations

derived from diamines.

Still another interesting aspect of this proposed

reaction is its possible application to tris(boranes)

derived from tertiary triamines. If an amount of iodine







necessary to iodonate only one of the borane entities is

employed, a new class of compounds might result, in which

both a boryl (BH2+) and borane (BH3) functionality are

present in the same molecule.


R2N NR NR23B[H3 2I2 R2N PI4R2 -I G
B/ BH3
H2
R= alkyl


This proposal was indeed found to be applicable to

both bis (boranes) and tris(boranes), and provides a very

general, high yield method of synthesis of cyclic boronium

cations.













CHAPTER II

MATERIALS AND INSTRUMENTATION


Materials

Samples of 2,2'-dipyridylketone and 2,2'-pyridil were

obtained from Aldrich Chemical Company, Inc. in 97% purity.

Sodium borohydride was obtained from Fisher Chemical

Company in good purity.

The various polyamines were obtained from either Aldrich

Chemical Company, Inc., Peninsular Chemical Company, or ICN

Life Sciences Group (K&K), dried over Molecular Sieves 3A,

and used without further purification.

Cylinder gases were obtained from Matheson Company, and

were used without further purification.

Ammonium hexafluorophosphate was obtained from Ozark-

Mahoning Company and was used without further purification.

Amine-boranes were obtained from Callery Chemical

Company, and were used without further purification.

Methyl fluorosulfonate (Magic Methyl) was obtained from

Aldrich Chemical Company, Inc. and was used without further

purification.

All solvents, except 1,2-dimethoxyethane (monoglyme),

supplied by various commercial sources, were used without

further purification except for drying over calcium hydride

or Molecular Sieves 3A. Monoglyme was treated with alumina








to remove any peroxides, stored over calcium hydride for a

few days and then fractionally distilled from lithium

aluminium hydride, saving the middle 80%.


Instrumentation

Infrared spectra were obtained on a Beckman IR-10

spectrophotometer. Samples were prepared as KBr pellets.

Liquid amines were run neat, if possible, using either

sodium chloride or potassium bromide plates.

Proton nmr spectra were taken on a Varian A-60 instru-

ment with tetramethylsilane as internal reference. lB nmr

spectra were run at 32.1 MHz with trimethylborate as an

external standard.

Ultraviolet and visible spectra were obtained on a

Beckman DB-G spectrophotometer using 1 cm square, fused-silica

cells.

Melting points were taken on a Thomas-Hoover apparatus

and were not corrected.

Elemental analyses were obtained from Galbraith Labora-

tories, Inc., or Atlantic Microlab, Inc.

All pH measurements were taken with a Corning 12 Research

pH meter with a Beckman Ag-AgCl glass electrode vs. a

saturated calomel electrode.












CHAPTER III

SYNTHESIS OF 2,2'-DIPYRIDYLMETHANE AND DERIVATIVES


Two methods for the preparation of 2,2'-dipyridylmethanol

were investigated.. The first employs the direct reduction

of 2,2'-dipyridylketone with aqueous sodium borohydride.

0 OH

NaBH




The second method of synthesis involves a multistep

approach, as described by Klosa,19,20 in which 2,2'-pyridil

undergoes a base promoted benzilic acid type of rearrange-

ment. The resulting acid salt is readily decarboxylated

under acidic conditions, yielding 2,2'-dipyridylmethanol.


0 0 HO CO OH

H +



Attempts to reproduce the reported procedure resulted in

considerably lower yields than those reported. The ready

availability of the starting material, however, makes this

procedure attractive, especially when large quantities of

2,2'-dipyridylnethanol are desired.

Synthesis of 2,2'-dipyridylmethanol from 2,2'-dipyridyl-

ketone and aqueous sodium borohydride. A 3mrle of

2,2'-dipyridylketone (25.0 g, 97% purity, 132 mmol) was

14









dissolved in H20 (150 ml). To this solution was added

NaBH4 (7.0 g, 185 mmol). The mixture was magnetically

stirred for 10 hours to ensure complete reaction, and ex-

tracted with four portions (100 ml) of CH2Cl2. The combined

CH2C12 extracts were dried over anhydrous Na2SO4, filtered,

and the CH2Cl2 removed under reduced pressure. The remaining

brown, viscous oil was distilled under reduced pressure.

The 2,2'-dipyridylmethanol obtained was a colorless, almost

odorless, viscous oil, bp 106-1100 at .2 mm (yield 22.5 g,

91.9%), which rapidly darkened on exposure to air. Anal.

Calcd. for C IH IN20: C, 70.99; H, 5.38; N, 15.05. Found:
11 10 2
C, 70.02; H, 5.44; N, 14.59.

Proton nmr in CCl4: broad doublet at -5.88 ppm, and

three multiplets centered at -6.94 ppr, -7.47 ppm, and -8.37

ppm, with an intensity ratio of 2:2:4:2, respectively.
-1
Infrared: characterized by strong absorption at 3200 cm-

assigned to OH stretch, and by the absence of any carbonyl
-i
absorptions in the region 1600-1750 cm Additional absorp-

tions: 1590 (s), 1570 (s), 1470 (s), 1435 (s), 1400, 1310,

1210, 1150, 1100, 1050 (s, broad, structured), 860, 760 (s,
-1
broad, structured) cm

Synthesis of 2,2'-dipyridylmethanol from 2,2'-pyridil.

The synthetic procedure employed was identical to that
20
described by Klosa.20 The yield (60%), however, was con-

siderably lower than reported (90%), for no apparent reason.

The product was identical to that obtained from the aqueous

sodium borohydride reduction of 2,2'-dipyridylketone.








Synthesis of 2,2'-dipyridylchlorciethane.



KH3(CH-2)7-3P
+ CHJ. + H3(CF L jRO -0 CHCI3


A sample of 2,2'-dipyridylmethanol (15.0 g, 80.6 mmol) was

dissolved in dry CC14 (150 ml). To this mixture, which was

cooled in an ice bath, was added dropwise, tri-n-octylphosphine

(44.8 g, 120.0 mmol) over a 30 minute period. Upon completion

of addition, the deep red solution was stirred for three

hours and extracted with four portions (100 ml) of 6N HC1.

This extraction was often complicated by the formation of

a gelatinous suspension. Dispersion of this sus-ension was

accomplished by the addition of CHCl3; volumes required

varied, but often approached 600 ml. The combined aqueous

acid extracts were further extracted with two portions

(100 ml) of CH2C12, to insure complete removal of any tri-n-

octylphosphine or tri-n-octylphosphine oxide carried over in

the initial extraction. The aqueous acid solution was

cooled in an ice bath, and CH2Cl2 (200 ml) was added. To

this magnetically stirred mixture was added concentrated

aqueous ammonia until the solution became alkaline (pI 11).

The rate of addition was such to prevent boiling of the

CH Cl After separation of the CH-CI from the aqueous
2 2 -2
solution, the aqueous solution was further extracted with

two portions (50 ml) of CH2C12. To the combined CH2C12

extracts was added, with stirring, approximately 5 g of

Norite (decoorizing charcoal). The mixture was filtered,








dried over anhydrous Na2SO4, filtered, and the CH2 2 removed

under reduced pressure. The remaining brown solid was re-

crystalized from petroleum ether (bp 65-1100), yielding

long, colorless needles, mp 73-740 (yield 14.90 g, 90.4%),

which were not sensitive to air. Anal. Calcd. for C1H19N2Cl:

C, 64.54; H, 4.40; N, 13.69; Cl, 17.36. Found: C, 64.45;

H, 4.46; N, 13.71; Cl, 17.36.

Proton nmr in CC14: singlet at -612 ppm, and three

multiplets centered at -7.09 ppm, -7.60 ppm, and -8.49 ppm,

with an intensity ratio of 1:2:4:2, respectively.

Infrared: absorptions at 2990, 1599 (s, broad, struc-

tured), 1540, 1478, 1310, 1150 (w), 1095 (w), 995 (s),

700 (s, broad, structured), 595 cm-1

Synthesis of 2,2'-dipyridylmethane from 2,2'-dipyridyl-

chloromethane.




SHOI Hc



A sample of 2,2'-dipyridylchloromethane (15.0 g, 73.3 rmnol)

was dissolved in 8N HC1 (200 ml). To this solution was

added slowly, zinc powder (20.0 g, 0.306 mmol). The

mixture was magnetically stirred for 20 hours to insure

complete reaction. The resulting solution was cooled,

made alkaline by the addition of concentrated aqueous ammonia,

filtered, and extracted with four portions (75 ml) of CH 2C12.

The combined CH Cl2 extracts were dried over anhydrous







Na2SO4, filtered, and the CH2C12 removed under reduced

pressure. The proton nmr of the remaining brown mobile

oil (11.5 g) revealed only the presence of 2,2'-dipyridyl-

methane. The oil was distilled under reduced pressure,

yielding a pale yellow, almost odorless oil, bp 1250 at

2 mm (yield 10.2 g, 82%), which darkened upon exposure to

air. Anal. Calcd, for C1lHN1N2: C, 77.64; H, 5.88;

N, 16.47. Found: c, 77.44; H, 5.96; N, 16.49.

Proton nmr in CC14: sharp singlet at -4.21 ppm, and

two doublets centered at -7.19 ppm, and -8.42 ppm, with an

intensity ratio of 2:6:2, respectively.

Infrared: absorptions at 3060 (w), 3000 (w), 1590 (s),

1570 (s), 1470 (s), 1432 (s), 1310 (w), 1210 (w), 1150 (w),

1100 (w), 1050 (w), 999 (s) 755 (s), 630 (w), 610 (w) cm- .

Direct synthesis of 2,2'-dipyridylmethane, starting

with 2,2'-dipyridylketone. A pure sample of 2,2'-dipyridyl-

methane can be obtained through a continuous reaction se-

quence of the before-mentioned reactions, eliminating the

need of isolation of each intermediate.

A sample of 2,2'-dipyridylketone (25.0 g, 97% purity,

132 mmol) was dissolved in H20 (150 ml). To this solution

was added sodium borohydride (7.0 g, 185 mmol). The mixture

was magnetically stirred for 10 hours to insure complete

reaction. The aqueous solution was extracted with four

portions (100 ml) of CH2Cl2. The combined extracts were

dried over anhydrous Na2SO4, filtered, and the CH2Ci2 re-

moved under reduced pressure. To the remaining brown, viscous







oil was added dry CCl4 (200 ml). To this mixture, which was

cooled in an ice bath, was added tri-n-octylphosphine (73.9 g,

198 mmol) over a one hour period. Upon completion of the

addition of tri-n-octylphosphine, the resulting deep red

solution was extracted with four portions (100 ml) of 6N HC1.

If the extraction resulted in a gelatinous suspension, CHC13

was added to disperse it, as described in the synthesis of

2,2'-dipyridylchloromethane. The combined aqueous acid

extracts were further extracted with two portions (100 ml) of

CH2C12 to insure complete removal of any tri-n-octylphosphine

or tri-n-octylphosphine oxide carried over in the initial

extraction. To the aqueous acid solution was added slowly,

zinc powder (40.0 g, 612 mmol) over a 20 minute period.

The mixture was magnetically stirred for 20 hours to ensure

complete reaction. The resulting solution was cooled in an

ice bath, made alkaline by the addition of concentrated

aqueous ammonia, filtered, and extracted with four portions

(150 ml) of CH2C12. The combined CH2C12 extracts were dried

over anhydrous Na2SO4, filtered, and the CI2C12 removed under

reduced pressure. The remaining brown oil was distilled under

reduced pressure. The 2,2'-dipyridylmethane obtained was a

pale yellow mobile oil, bp 1250 at 2 nm (yield 20.5 g,

91.4%), which darkened upon exposure to air. This material

was found to be identical to that of an authentic sample.







Synthesis of 2,2'-dipyridylmethane-ammonium (2+) bromide.



2HBr(g) ci2HBr



A sample of 2,2'-dipyridylmethane (3.00 g, 17.6 mmol), dis-

solved in CH2Cl2 (300 ml), was saturated with anhydrous

hydrogen bromide and magnetically stirred for one hour to

ensure complete reaction. The resulting white precipitate

was removed by vacuum-filtration, washed with two portions

(50 ml) of diethyl ether, and vacuum-dried (yield 5.71 g,

97.4%); mp 2740. Anal. Calcd. for CllH12N2(2+), 2Br-:

C, 39.76; H, 3.61; N, 8.43; Br, 48.19. Found: C, 39.56;

H, 3.67; N, 8.40; Br, 48.29.

Infrared: absorptions at 2600 (s, broad, structured),

1610 (s), 1535 (w), 1462 (w), 1395 (w), 1297 (s), 1222, 1159,
-i
1090 (w), 1000 (s), 956, 923, 760 (s), 620 cm1.

Synthesis of 2,2'-dipyridylmethane ammonium (1+) hexa-

fluorophosphate.



N H4 6 FPF



A sample of 2,2'-dipyridylmethane (1.0 g, 5.88 mmol) was

dissolved in 2N HCI (20 ml). To this solution was added

3 ml of 5M NH4PF6 and IN NaOH was added dropwise until the pH

of the solution was 4. At this point a crystalline material

formed and was removed by vacuum-filtration. The white

crystalline solid was recrystallized from hot water, filtered,








and vacuum-dried (yield 1.40 g, 75.3%); mp 95-960. Anal.

Calcd. for C11H11 N2+ PF6-: C, 41.77; H, 3.48; N, 8.86.

Found: C, 40.89; H, 3.55; N, 8.70.

Proton nmr in CH3CN: sharp singlet at -4.60 ppm, and

three complex multiplets centered at -7.67 ppm, -8.15 ppm,

and -8.31 ppm, with an intensity ratio of 2:4:2:2, respectively.

Infrared: strong absorption centered at 2600 cm-1,

assigned to N-H stretching mode.

Synthesis of 2,2'-dipyridylchloromethane ammonium (1+)

hexafluorophosphate.



CJ NH4P PF'6F



A sample of 2,2'-dipyridylchloromethane (1.0 g, 4.88 mmol)

was dissolved in 2N HC1 (15 ml). To this solution was added

3 ml of 5M NH4PF6, and IN NaOH was added dropwise until the

pH of the solution was 4. At this point, a heavy white

crystalline material formed and was removed by vacuum-filtra-

tion. The white crystalline solid was recrystallized from

hot water, filtered, and vacuum-dried (yield 1.50 g, 87.7%);

mp 156-1570. Anal. Calcd. for C11HIOCIN2 PF6-: C, 37.66;

H, 2.85; N, 7.99; Cl, 10.13. Found: C, 37.77; H, 2.93;

N, 8.02; Ci, 9.97.

Proton nmr in CH3CN: sharp singlet at -6.60 ppm, and

three complex multiplets centered at -7.85 ppm, -8.31 ppm,

and -8.80 ppm, with an intensity ratio of 1:4:2:2, respectively.








Infrared: broad band centered at 2900 cm-l1 assigned

to the N-H stretching mode. Additional absorptions: 1637 (s),

1600 (s), 1530, 1515, 1479, 1455, 1380, 1365, 1310, 1280,

1240, 1215, 1175, 1100, 1050, 1008 (s), 845 (broad, struc-

tured, assigned to PF6 ), 770, 740, 703, 650 (s), 622, 550 (s),

485 cm-1.

Synthesis of 2,2',2"-tripyridylmethane from 2,2'-dipyridyl-

methyl lithium and 2-bromopyridine.

Li
SH-+ LiBr
J Br 3


Phenyl lithium was prepared by dropping bromobenzene (4.00 ml,

40.0 mmol), in anhydrous diethyl ether (25 ml), onto lithium

chips (0.560 g, 80.7 mmol), suspended in anhydrous diethyl

ether (200 ml), in an inert atmosphere of nitrogen. After

stirring for two hours, all the lithium had dissolved, and

2,21-dipyridylmethane (6.70 g, 39.0 mmol), in anhydrous

diethyl ether (30 ml), was slowly added. Stirring was

continued for one-half hour, during which time the mixture

became orange in color. To this orange solution was added

2-bromopyridine (6.32 g, 40.0 mmol), dissolved in anhydrous

diethyl ether (30 ml). The solution was refJuxed for 45

minutes to ensure complete reaction, and poured onto crushed

ice (200-300 g). The phases were separated and the aqueous

layer was extracted with three portions (100 ml) of CH2C12.

The ether and CH2C12 solutions were combined, dried over








anhydrous Na2SO4, filtered, and the volatiles removed under

reduced pressure. The remaining brown solid was recrystallized

from hot heptane. The 2,2',2"-tripyridylmethane obtained

was a pale yellow, crystalline solid (yield 6.3 g, 76%);

mp 100', which was not air sensitive. Anal. Calcd. for

C16H13N3: C, 77.73; H, 5.26; N, 17.00. Found: C, 77.69;

H, 5.30; N, 16.92.

Proton nmr in CCi4: sharp singlet at -5.81 ppm, and

two corjrlex multiplets centered at -7.25 ppm, -8.40 ppm,

with an intensity ratio of 1:9:3, respectively.

Infrared: absorptions at 3060 (w), 1593 (s), 1575 (w),

1470 (w, structured), 1439 (s), 1151 (w), 1090 (w), 1050 (w),

996 (w), 780 (w), 752 (s) cm-1.

The yields, melting points, and boiling points of all

compounds in this chapter appear in Table I.











Table I


Yields, Melting and Boiling Points of
2,2'-Dipyridylmethane and Derivatives


Compound


Yield %


Mp 0


Bp C


OH




cl










-H
3





SPFG
'HPii

,HP F6


91.9




90.4


82.0




76.0




75.3




87.7


106-110
.2mm


73-74


125
.2mm


100


126-132a
5mm


100-101a


95-96




156-159


a C. Osuch and R. Levine, J. Am. Chem. Soc., 78, 1723(1956)


Lit


~~


~~___________~_______________












CHAPTER IV

SYNTHESIS OF POLYAMINE-BORANES


Borane adducts of polyamines containing two or more

tertiary nitrogen atoms, are prepared by three apparently

general synthetic methods.21-24 These syntheses proceed

from (1) sodium borohydride and acid salts of polyamines,

(2) trimethylamine-borane and polyamine, or (3) sodium boro-

hydride, iodine and polyamine. The general procedures and

usefulness of each synthetic method are illustrated, and

referred to as general procedures 1, 2, and 3, respectively,

in the description of synthesis of various polyamine-boranes.

New polyamine-boranes were satisfactorily characterized by

elemental analysis, and their infrared and proton nmr spectra.

Synthesis of 2,2'-dipyridylmethane-bis(borane).



2NBHi2Hr I .2BH3. 2H2 2NOBr



To a magnetically stirred slurry of 2,2'-dipyridylmethane-

ammonium (24) bromide (2.39 g, 7.20 mmol), in dry peroxide-

free 1,2-dimethoxyethane (100 ml), was added sodium boro-

hydride (94% hydride purity, 0.606 g, 16.0 mmol, 10% ex-

cess). Vigorous evolution of hydrogen ensued, and stirring was

continued for two hours or until hydrogen evolution ceased.

The volatiles were removed under reduced pressure, and the re-







mining white solid was extracted with two portions (20 ml)

of CH2Cl2 to remove the soluble bis(borane) from sodium

bromide and unreacted sodium borohydride. The two CII2Cl2

extracts were combined and hexane (150 ml) was addod, pro-

ducing a white precipitate. This material was removed by

vacuum-filtration, and vacuum-dried (yield 1.32 g, 92.3%);

mp 1450. (turns red at 1300 and melts with decomposition

at 1450). Anal. Calcd. for CllHI5B2N2: C, 66.66; H, 8.08;

N, 14.14; B, 11.12. Found: C, 66.39; H, 8.22; N, 13.93;

B, 11.29.

Proton nmr in CDCl3: sharp singlet at -3.49 ppm, and

three complex multiplets centered at -7.29 ppm, -7.88 ppm,

and -8.82 ppm, with an intensity ratio of 2:4:2:2, respec-

tively.
-1I
Infrared: strong absorption centered at 2350 cm ,

assigned to B-H stretching mode. Additional absorptions:

1626 (s), 1580 (w), 1590 (s, broad, structured), 1452, 1440,

1420, 1189 (s), 1162 (s), 1110, 1089, 935, 762 (s) cm- .

Synthesis of N,N,N',N'-tetramethylethanediamine-

bis(borane).


Me2N(CH22NMe2 +2Me3NBH3 --- Me2N(CH2)2NMe22BH3 2Me3N



Trimethylamine-borane (8.07 g, 111 mmol) and freshly distilled

N,N,N' .N'-tetramethylethanediamine (6.47 g, 55.6 mmol) were

combined with benzene (30 ml) in an Erlenmeyer flask (50 ml)

fitted with a reflux condenser and a T-adapter, through which

nitrogen gas was passed to remove liberated trimethylamine.








The mixture was magnetically stirred and heated in an oil

bath at 800 for 6 hours, with continuous nitrogen flushing.

To the mixture, containing a white solid, was added petroleum

ether (50 mi). The solution was vacuum-filtered, and the

solid placed in a vacuum sublimator and pumped on overnight.

Bis(borane) (7.55 g, 52.5 mmol, yield 93%) was recovered,

mp 1830, lit., 25-27 182:5-185.

The proton nmr and infrared spectra were identical to
25-27
those previously reported.25-27

V'y. t}. i. of 2- (p-:T- p ,-p r.ci .*oeth','1)t,'viC ^e-ii ( ,.- :-..- .r i I1 1




(CH2)2N 2NaBH4 4 12 CH-> NJJ lN 22I + H


Sodium borohydride (2.19 g, 57.9 mmol, 10% excess) and 2-(2-N-

pipeR.idinoethyl) pyridine (500 g, 26.3 iaimol) were suspended in

dry Tr7orIy::, 0, (60 ml) in a two-neck flask (250 ml), fitted

with a pressure-compensating dropping funnel, and outlet

tube leading to a bubbler containing a benzene-amine mixture,

as describLed by Nainan.28 To this slurry was added dropwise,

iodine (6.70 g, 26.4 mmol), dissolved in monoglynme (40 ml),

over a one hour period. The mixture was stirred throughout

the reaction, while hydrogen gas escaped through the bubbler.

The solvent was removed under vacuum, and the resulting solid

was extracted with dry CH2C12 (100 ml) to separate the sol-

uble amine-borane from sodium iodide and unreacted boro-

hydride. The CH2Cl2 was removed under vacuum, and the remaining








solid was washed with water (50 ml) to remove any sodium

iodide that was solubilized by the borane. The product was

vacuum-dried for 10 hours (yield 5.36 g, 93.3%); mp 105.

Anal. Calcd. for C12H24B 22: C, 66.06; H, 11.01; N, 12.84.

Found: C, 65.83; H, 10.88; N, 12.56.

Proton nmr in CH2Cl2: six complex multiplets centered

at -1.67 ppm, -3.00 ppm, -3.70 ppm, -7.38 ppm, -7.89 ppm,

and -8.65 ppm, with an intensity ratio of 6:4:4:2:1:1,

respectively.

Infrared: strong absorption centered at 2320 cm-1,

assigned to the B-H stretching mode. Additional absorptions:

2900 (s, broad, structured), 1619 (w), 1576 (w), 1489 (s),

1472, 1445 (s), 1180 (s, broad, structured), 1116 (w),

1080 (w), 1025 (w), 972, 760 (s) cm-1.

Synthesis of 2,2'-dipyridyl-bis(borane).




S2HBr + 2NaBH4 --> 2BH3 2NaBr + 2H2



A sample of 2,2'-dipyridyl-ammonium (2+) bromide (9.4014 g,

29.6 mmol) was reacted with sodium borohydride (2.46 g,

65.1 mmol, 10% excess), according to procedure (1). After

removal of the volatiles, the remaining solid was washed with

water (50 ml). The insoluble bis(borane), a white crystalline

solid, was collected by vacuum-filtration, and vacuum-dried

overnight (yield 4.80 g, 88.2%). The compound does not melt

up to 3000, as reported.22








The proton nmr and infrared spectra were identical

to those of an authentic sample.

Syntheses of N,N'-dimethylpiperazine-bis(borane).


Me Me

*2HBr + 2NaBH4 -----> -2B-H3 + 2NaBr + 2H2

Me Mle


A sample of N,N'-dimethylpiperazine-ammonium (2+) bromide

(17.0 g, 61.6 mmol) was reacted with sodium borohydride

(5.83 g, 154 mmol, 10% excess), according to procedure (1).

After removal of the volatile a white crystalline solid

remained, which was redissolved in CH 2C12 (30 ml) and

precipitated by the addition of hexane. The bis(borane)

obtained was vacuum-dried for five hours (yield 8.02 g,

91.7%) np 1790. Anal. Calcd. for C6H20B2N2: C, 50.70;

H, 14.08; N, 19.72. Found: C, 50.63; H, 14.27; N, 19.68.

Proton nmr in CH2Cl2: broad singlet at -2.17 ppm,

and a complex multiple shouldering this singlet centered

at -3.10 ppm, with an intensity ratio of 6:8, respectively.
-1
Infrared: strong absorption centered at 2350 cm ,

assigned to the B-H stretching mode. Additional absorptions:

3110 (w), 2960 (w), 2090 (w), 1450 (s, structured), 1330,

1300 (s), 1190 (s), 1150 (s, doublet), 1120 (s), 1100,

1032 (s), 990 (s), 995 (s), 859 (s) cm-1.








Syiint1he1- s of 1,2 (:i,:;' -bi s-pieridin ) eta e.no-bis (bc:rane).



(C '2N 2HBr + 2NuBH4---> O '-2 -2BH3 2NaBr +2H2



A sample of 1,2(N,N'-bis-piperidine)ethane-airmonium (2+)

bromide (19.5 g, 56.0 mmol) was reacted with sodium boro-

hydride (5.30 g, 140 mmol, 20% excess) according to procedure

(1). The product was collected by vacuum-filtration, and

vacuum-dried for 10 hours (yield 10.1 g, 47.2 nmmol, 84.3%

of bis(borane)); mp 2050. Anal. Calcd. for C,2H B N2:

C, 64.29; H, 13.39; N, 12.50. Found: C, 64.23; H, 13.53;

N, 12.49.

Proton nmr in CH2C12: two broad complex multiplets and

a singlet centered at -1.66 ppm, -2.83 ppm, and -3.14 ppm,

with an intensity ratio of 12:8:4, respectively.

Infrared: strong absorption centered at 2350 cm-,

assigned to the B-H stretching mode. Additional absorptions:

2960 (s), 2940 (s), 1480, 1449 (s), 1409 (w), 1331 (s),

1300 (s), 1275 (w), 1190 (s), 1180 (s), 1150 (s), 1082 (s),

1040 (s), 980 (s), 954 (s), 910 (s), 860 (s), 810 (w),

772 (s) cmnl.

Synthesis of 2-(2-dimethylaminoethyl) pyridine-bis(borane).


.2H3r .2N aS0rsi2 F12
(C H2)2NMe:2 +2NaBH4 --(C42)2NMe2 2BH3 2NB 2



A sample of 2-(2-dimethylaminoethyl) pyridine-amnionium (2+)

bromide (5.0 g, 16.0 mmol) was reacted with sodium borohydride








(1.40 g, 40.0 mmol, 20% excess) according to procedure (1).

After removal of the volatiles, the remaining white solid

was redissolved in CH2Cl2 (25 ml) and precipitated by

addition of hexane. The bis(borane) obtained was vacuum-

dried for five hours (yield 2.40 g, 84.3%); mp 1000. Anal.

Calcd. for C9H20B2N2: C, 60.67; H, 11.24; N, 15.73. Found:

C, 60.81; H, 11.44; N, 15.62.

Proton nmr in CH2Cl2: sharp singlet at -2.65 ppm, and

five complex multiplets centered at -3.08 ppm, -3.65 ppm,

-7.48 ppm, -7.90 ppm, and -8.67 ppm, with an intensity

ratio of 6:2:2:2:1:1, respectively.

Infrared: strong absorption centered at 2330 cm-,

assigned to the B-H stretching mode. Additional absorptions:

1620 (w), 1578 (w), 1462 (s, broad, structured), 1319,

1170 (s, broad, structured), 1100 (w), 1092 (w), 1035, 1015,

990, 930, 840 (w), 820 (w), 765 (s) cm- .

Synthesis of 2-(2-N-pyrrolidinoethyl)pyridine-bis(borane).




SCH2N + 2NaBH4 2 (- CH22 | 2BH3+2NaGi + 12


A sample of 2-(2-N-pyrrolidinoethyl)pyridine (5.0 g, 28.4 mmol),

was reacted with sodium borohydride (2.47 g, 65.3 mLmol,

15% excess) and iodine (7.2 g: 28.4 mmol) according to

procedure (3). After removal of the volatiles, the white

solid was extracted with CH2Cl2 (100 ml), to separate the

soluble bis(borane) from sodium iodide and unreacted sodium







bo:ohydride. The CH2Cl2 was removed uni.r vacuum, ian. the

solid was washed with water (50 ml) to remove any sodium

iodide that was solubilized by the borane. The product

was vacuum-dried for 10 hours (yield 5.35 g, 92.4%);

mp 960. Anal. Calcd. for C11H22B2N: C, 64.71; H, 10.78;

N, 13.73. Found: C, 64.50; H, 10.68; N, 13.62.

Synthesis of N,N,N',N'-tetramethyl-l,3-propanediamine-

bis(borane).


Me2N(CH2)3NMe2 + 2Me3NBH3 Me2N(CF2)3NMe2 2BH3 + 2Me3N



Samples of N,N,N',N'-tetramethyl-1,3-propanediamine (7.25 g,

55.6 mmol) and trimethylamine-borane (8.04 g, 110 mmol)

were reacted according to procedure (2) for 30 hours. A

white solid was collected (yield 7.95 g, 90.3%); mp 146,

lit.26,27 144-1450.

The proton nmr and infrared spectra were identical to

those of an authentic sample.

Synthesis of N,N,N',N'-tetramethyl-1,4-butanediamine-

bis(borane).


Me2N(CH2)4NMe2 + 2Me3NBH3 ----- Me2N(CH24NMe22BH3 + 2Me3N


Samples of N,N,N',N'-tetramethyl-l,4-butanediamine (4.35 g,

30.2 mmol) and trimethylamine-borane (4.24 g, 58.0 mmol)

were reacLed according to procedure (2) for 30 hours. A

white solid was collected (yield 4.34 g, 87.9%); mp 151,








lit.26,27 147-149.

The proton nmr and infrared spectra were identical to

those of an authentic sample.

Synthesis of N,N,N' ,N'- te.tramethyl-1,6-hexanediamine-

bis (borane).


MeN(CtH2)6NMe2 2Me3NBH3 --> Me2N(CH26NMe2-2BH3 + 2Me3N


Samples of N,N,N'N'-tetramethyl-1,6-hexanediamine (4.95 g,

28.8 mmol) and trimethylamine-borane (4.38 g, 60.0 rine))

were reacted according to procedure (2) for 30 hours. A

white solid was collected (yield 5.15 g, 89.4%); ii-n 1030

Proton nmr in CH C12: two complex multiplets, one of

which overlapped a broad singlet. The chemical shift of

this multiple could not be assigned exactly, due to this

overlap. The upfield multiple and singlet were centered

at -1.57 ppm, and -2.52 ppm.

Infrared: strong absorption centered at 2320 cm-',

assigned to the B-H stretching mode. Additional absorptions:

2950 (s, broad, structured), 1470 (broad doublet), 1410,

1392, 1250, .230, 1190 (s), 1.168 (s), 1140, 1062, 1015,

991 (w), 971 (s), 870 (s), 792, 730 cm 1.

Synthesis of N,N,N',N'-tetramethyl-!,2-propanediaminie-

bis (borane).

Me Me
Me2NCHCH2NMe2 + 2Me3NBH3 Me2NCHCH2NMe2-2BH3 + 2Me31


Samples of N,N,N',N'-tetramethyl-l,2-propanediamn ne (5.20 g,






40.0 mmol) and trimethylamine-borane (6.21 g, 85.1 mmol)

were reacted according to procedure (2) for 40 hours. A

white solid was collected (yield 5.72 g, 90.5%); mp 116.

Anal. Calcd. for C7H24B2N2: C, 53.16; H, 15.19; N, 17.72.

Found: C, 53.22; H, 15.34; N, 17.81.

Proton nmr in CH2Cl2: doublet, two broad singlets,

and a complex multiple system encompassing the two singlets.

The doublet was centered at -1.55 ppm, and the two singlets

at -2.48 ppm, and -2.65 ppm.

Synthesis of N,N,N',N'-2-pentamethyl-l,3-propanediamine-

bis (borane).

Ye Me
e2NCH.:HCH2NMe2 + 2Me3NBH3 --- Me2NCHCHCH2NMe 2BH3 + 2Me3N


Samples of N,N,N',N'-2-pentamethyl-1, 3-propanediamine

(4.00 g, 27.7 mmol) and trimethylamine-borane (5.06 g,

69.3 mmol) were reacted according to procedure (2) for

40 hours. A white solid was collected (yield 3.80 g, 79.8%);

mp 960. Anal. Calcd. for C8H26B2N2: C, 55.81; H, 15.12;

N, 16.28. Found: C, 55.72; H, 15.21; N, 16.37.

Proton nmr in CD3CN: sharp singlet at -2.60 ppm, a poorly

resolved doublet centered at -2.07 ppm, and a complex multiple

underneath the singlet centered at approximately -2.67 ppm.

Synthesis of Pentamethyldiethylenetriamine-tris(borane).

MIe 3 e + 3
Me2N(CH)2N(CH)22NMe2 3BH4 212--- MeN(CH2)2N(CH22NtMe2 3BH3 + 31 + 22


Samples of pentamethyldiethylenetriamine (1.00 g, 57.7 mmol),








sodium borohydride (7.53 g, 199 mmol, 15% excess) and

iodine (22.0 g, 86.6 mmol) were reacted according to pro-

cedure (3). After removal of the volatiles, the white

solid was extracted with three portions (100 ml) of water

to remove any unreacted sodium borohydride and sodium

iodide, vacuum-dried, and recrystallized from not acetone

(yield 10.0 g, 81.4%); mp 1850, lit.28-30 185-1860. Anal.

Calcd. for CgH31B3N3: C, 50.23; H, 14.88; N, 19.53.

Found: C, 50.35; H, 14.21; N, 19.86.

The proton nmr and infrared spectra were identical to

those previously reported.28-30

Synthesis of :- pethyl-N'- (2-dimethylaminoethy )piper-

azine-tris(borane).



MeN (CHiNMe2 38H4 212 --> MeO CH M NMe23BH3 31- H2



Samples of N-methyl-N'-(2-direthylaminoethyl)piperazine

(5.00 g, 29.2 mmol), sodium borohydride (3.81 g, 101 mmol,

15% excess), and iodine (11.1 g, 43.9 mmol) were reacted

according to procedure (3). After removal of the volatiles,

the remaining white solid was washed with three portions

(50 ml) of water to remove unreacted sodium borohydride

and sodium iodide, and vacuum-dried (yield 5.83g, 93.6%);

mp 1650. Anal. Calcd. for C91130B3N3: C, 50.70; H, 14.08;

N, 19.72. Found: C, 50.88; H, 14.23; N, 19.83.







Proton nmr in CH2C12: broad singlet at -2.64 ppm, and

two complex multiplets centered at -2.84 ppm, and -3.42 ppm.

Due to the overlap of absorptions, definitive integration

was not possible.

Infrared: strong absorption centered at 2350 cm-l,

assigned to B-H stretching mode. Additional absorptions:

1460 (s), 1405 (w), 1345 (w), 1330, 1298, 1200 (s), 1187 (s),

1162 (s), 1137, 1112, 1082, 1017, 990 (s), 965, 928, 897,

869 (s), 841, 828, 802, 780, 600 cm-1.

Synthesi~; of 2- (trihydroborondi rethvlaminomethyl)pyridine.




UCH2NMe' + 2McNBH3-- CHNiMe2 > Me3N + Me3NBH3


Samples of 2-(dimethylaminoinethyl)pyridine (2.50 g, 184 mmol)

and tririethylamine-borane (1.83g, 2.50 mmol) were reacted

according to procedure (2) for 30 hours. A white solid

was collected (yield 2.25 g, 81.5%); mp 550. Anal. Calcd.

for C.H1IBy2: C, 64.00; H, 10.00; N, 18.66. Found:

C, 63.84; H, 10.30; N, 18.67.

Proton nmr in CHi2C12: two singlets centered at -2.60 ppm,

and -4.03 ppm, and three complex multiplets centered at

-7.30 ppm, -7.71 ppm, and -8.60 ppm, with an intensity ratio

of 6:2:2:1:1, respectively.

Infrared: strong absorption centered at 2340 cm-I,

assigned to B-H stretching mode. Additional absorption:

3020 (s), 2985 (s), 2080, 1600 (s), 1580 (s), 1472 (s),







1440 (s), 1412, 1365, 1337, 1295, 1230, 1212, 1179 (s),

1150 (s), 1140 (s), 1112, 1090, 1060, 1020 (s), 1000 (s),

980, 940, 910, 870 (s), 826 (s), 769 (s), 759 (s), 702 (s),

610, 510 (s), 440, 411 (s), 370 cm-1

Synthesis of 4(N,N-dimethylamino)pyridine-borane.


NMe2 NIMe2

+ Me3NBH3 ---- Me3N

H3

Samples of 4-(N,N--dimethylamino)pyridine (3.00 g, 246 mmol)

and trimecthylamine-borane (2.69 g, 3.69 mmol) were reacted

according to procedure (2) for 30 hours. A white solid

wa. collected (yield 3.03 g, 90.7%); mu 1690. Anal. Calcd.

io: C7H13BN2: C, 61.76; H, 9.56; N, 20.58. Found: C, 62.50;

II, 9.81; N, 20.55.

Proton nmr in CH2Cl2: sharp singlet at -3.03 ppm,

and two complex multiplets centered at -6.46 pplm, and -7.93 ppma.

with an intensity ratio of 6:2:2, respectively.

Infrared: strong absorption at 2300 cm-, assigned to

E-Hi stretc!,hing mode. Additional absorption: 2938 (w),

(640 (s), 1550 (s), 1.450 (s), 1398 (s), 1346, 1310, 1230 (s),

1178 (s), 1130, 1100 (s), 1068, 1040, 943, 812 (s), 512 (s),

486 cm-1.

The yields and melting points of a]i polyamine-boranes

contained in this chapter appear in Table II.












Table II


Yields and Melting Points of Polyamine-Boranes


Compound


Me2N (C H2)2 N M e2 2BH3

Me2" r.1.[ .N""' !C -22 H3

Me2N(CHi.- K;' 2- 2BH3

M ... -' 'i -2'2 BH3
M ...,, 2 ] i ;.,,' 2 2 B H 3

Me
MeP2NCHHCH2 C HN Me2 2BH3

Me2 .HCICHNMc2 2DBH3

Me
Me2 ...I.2) J(c h2) Me2 3BH3




i 2BH3



M .-- l.2BH3
i ." .

K l. !, t'223



Men !.'Ml 2BH3

/__j2 3


Yield % Mp C Lit


93.0

90.3

87.0

89.4


79.8


90.5


81.4


92.3



88.2


84.3


34 .3


183

146

151

103


96

116


182.5-185a'b


144-149 5bc
147-14.9bc


185-186


145



300


205



179


1 O0


185--186d f











Table II (continued)

Compound Yield Mp oC Lit


(CH )2 2BH3 93.3 105


Me N(CH-22NMe2.3BH3 93.6 165


-1-NMe2B\3 90.7 169



i JCH2N MeBH.: 81.5 55



S(CH2 2 *2BH3 92.4 96


a IT E. miller and E. L. iu.,Atterties, J. Am. Chem. Soc.,
86, 1033(i); b *'. E. Sullivan, Doctoral Dissertation,
University of Florida, (1970); c G. E. Rvschrewi-tsch a i
T. o c{ .li.van, ,-. .'1_ .,_%, 899(1970); d K. C. rai. .,
Doctoral D.ssertation, University of Florida, (1969);
e FE. !Walker and R. K. Pearson, rT. Inorr. Nucl._ Chem.,
2., 198i (1965); f K C. zainw:0 and G. E. Ryschkewitschi,
J. Am,_ Ch.. c., 91, 0(1969); g K. C. Nainan and
G. E. Rych:newitsch, Inorg,. emni., 8, 2671(1969).












CHAPTER V

SYNTHESIS OF CYCLIC BORONIUM CATIONS DERIVED
FROM TERTIARY POLYAMINE-BORANES


Cyclic Cations Derived from Reactions of
Polyamine-Boranes with Iodine
or Trimethylamine-Iodoborane

A new, rapid and high yield synthesis of cyclic boronium

cations is described in this chapter. Reaction of polyamine-

boranes derived from tertiary polyamines, as described in

the previous chapter, with iodine or trimethylamine-

iodcborane under appropriate conditions, provides high

yields of cyclic boronium cations. Iodine is the preferred

reactant for all polyamines investigated, except those

possessing sites which are reactive toward iodine or inter-

mediates produced during the reaction.

General procedure of synthesis. The apparatus consists

of a 250 T1 Erlenmeyer flask, fitted with a straight vacuum

distillation adapter, used for the passage of nitrogen into

the flask, and a reflux condenser. An outlet tube leading

to a bubbler containing a benzene-amnine mixture is attached

to the top of the condenser to trap diborane gas liberated

from the reaction. The apparatus was suitable for reactions

with either io,.rine or trimethylamine-iodoborane. In a

typical reaction a stoichiometric amount of iodine or tri-

mothylamine-iodoborane is allowed to react with a benzene








solution or slurry of the polyamine-borane, while being

heated just below reflux. Nitrogen gas is continuously

passed above the solution to remove diborane from the

reaction. Reaction times varied from 1 to 24 hours,

depending on the polyamine-borane employed. Ten hours,

however, was sufficient in all but a few cases. All salts

were converted to the more stable and more easily analyzed

hexafluorophosphates. Quantities were calculated on the

basis of the following equations:


R_ iRi2BH 2 /~\- 1
R2 RB *24 + 21 --> R2 NNR2I B2H6





H2
-v


Diborane generated in the above reactions can be re-

covered in high yields as polyamine-borane, suitable for

further reaction, if sufficient care is extended to exclude

all moisture and oxygen from the system, thus, conserving

an expensive reactant.

The general procedure is exemplified in the synthesis

of 2,2'-dipyridyimethanedihydroboron (1+) hexafluorophosphate,

and will be referred to as the "general procedure" throughout

this chapter.







Synthesis of 2,2'-dipyridylmethanedihydroboron (1)

hexaf] ~]ro I rphcsphate.



I 2BH3 6 ----- PF H
SN 1^ (2)NH4PF6
H2


To a stirred slurry of 2,2'-dipyridylmethane--bis(borane)

(1.00 g, 5.07 mmol) in dry benzene (100 ml) was added

solid iodine (0.647 g, 2.55 mmiol). An immediate reaction

ensued with the evolution of hydrogen gas and a dark brown

solution resulted. The flask was attached to a vacuum

distillation adapter and a reflux condenser, to which a

benzene-amine bubbler was attached. The reaction mixture

was heated just below reflux in an oil bath. The solution

became colorless and precipitation of a white solid ensued.

The presence of diborane above the reaction was confirmed by

its reaction with moist silver nitrate paper. Nitrogen

gas was passed continuously through the system to remove

the liberated diborane. The reaction an,:eared to be complete

within 2 hours, as evidenced by the absence of any further

diborane ',-.-eration. An additional 3 hours of reaction time

were employed to ensure complete reaction. Upon cooling,

the white solid was removed by vacuum-filtration, washed

with dry benzene (30 ml), diethyl ether (30 ml) and vacuum-

dried (yield 1.563 g, 99.3%).

Conversion to the hexafluorophosphate salt was accoi -lished

by dissoivinci the iodide salt (0.534 g, 1.72 mtol) in H20








(20 ml), and adding 51 NII4PF6 (2 ml). The mixture was

cooled in an ice bath, vacuum-filtered, washed with ice cold

water (30 ml), three portions (50 ml) of dry ether, and

vacuum-dried (yield 0.531 g, 94.1%); mp 1960, dec. Anal.

Calcd. for C11HI2BN2+, PF6: C, 40.24; H, 3.66; N, 8.54;

B, 3.29. Found: C, 40.29; H, 3.71; N, 8.52; B, 3.12.

Proton nmr in CH-3CN: singlet at -4.86 ppm and three

complex multiplets at -7.91 ppm, -8.33 ppm and -8.75 cpp1m,

with an intensity ratio of 2:4:2:2, respectively. The 11B

nmr in CH3CN: triplet at 23.1 ppm from trirmethylborate.

The B-H coupling constant was approximately 110 Hz.

Infrared: double centered at 2450 cm-1, assigned to

B-H stretching mode. Additional absorptions: 1640 (s),

1590 (w), 1500 (s), 1468, 1418, 1318, 1280 (w), 1222 (w),

1170 (w), 1138 (s), 1090, 840 (s, broad, structured, assigned

to PF6), 772 cm-1.

Synthesis of N,N,N',N'-totramethyl-1,2-ethanediamine--

dihydroboron (1+) hexafluorophosphate.


1-
(1) 2 2H
e2N(CH 2)NMeZ2BH3 R R2 PF2 '+ 82H
(2)N H4P r6 2
H2 R=Me

A sample of N,N,N',N'-tetramethyl-1,2-ethanediamine-bis(borane),

(1.00 g, 6.94 nmmol) was reacted with solid iodine (0.886 g,

3.49 mnol) in dry benzene, according to the general procedure.

The reaction appeared to be complete within 1 hour.

Heating was continued for an additional 3 hours to ensure

complete reaction. A white solid (yield 1.69 g, 95.4%) was

collected.







The iodide salt (0.748 g, 2.92 nnmol) was converted

to the hexafluorophosphate salt (yield 0.738 g, 92.3% recovery);

mp 2450, dec. lit.25-27 240-2440 dec. Anal. Calcd. for

C6H18 I2+, PF6: C, 26.30; H, 6.57; N, 10.23. Found:

C, 26.39; H, 6.78; N, 10.12.

The proton nmr and infrared spectra were identical

to those previously reported.25-27

Synthesis of N,N,N',N'-tetramethyl-l,3-propanediamine

dihydroboron (1+) hexafl uorophosphate.



(1) 2 PF
Me2N(CH2)3NMe22BH3 -- Mt-2N Me2 2 2H 5
(2) NH4PF6
H2

A sample of N,N,N',N'-tetramethyl-1,3-propaneediamne-

bis(borane) (1.00 g, 6.40 inmol) was reacted with solid

iodine (0.816 g, 3.21 nmol) in dry benzene, according tor

the gq'Peral procedure. After 8 hours of heating, only a

small amount of solid was present and diborane was still

being evolved. Heating was continued for an additional 18

hours to ensure complete reaction. A white solid (yield

1.64 g, 95.3%) was collected.

The iodide salt (1.04 g, 3.87 mmol) was converted to

the Ihexafluorophosphate salt (yield 0.901 g, 81.3% recovery);

mp 24'3, dec. lit.26,27 241-2450, dec. Anal. Calcd. for

C7H20 ';2+,PF'-: C, 29.19; H, 7.00; N, 9.73. Found:

C, 29.39; H, 7.45; N, 9.61.

The proton nmr and infrared spectra were identical to

i;.-:D previously reported.26,27








Sythesis of N,N,N',N'-tetramethyl-1,4-butanedianine-

dihydroboron (1") hexafluorophosphate.



(1) 2 '2 PF "
Me2N(CH2)4NMe22BH3 > Me Me- B-NMe2 6 26
(2) NH4PF6 H2


A sample of N,N,N',N'-tetramethyl-1,4-butanediamine-

bis(borane) (1.02 g, 5.93 mmol) was reacted wic.h solid

iodine (0.753 g, 2.96 mmol) in dry toluene,according to

the general procedure. After 6 hours of heating, only a

small amount of solid was present and diborane was still

being evolved. Heating was continued for an additional

18 hours to ensure complete reaction. A white solid

(yield 1.53 g, 90.8%) was collected. The iodide salt

(0.988 g, 3.48 mmol) was converted to the hexafluorophosphate

salt (yield 0.701 g, 66.7% recovery); mp 2300, dec. lit.26,27

230-2310 dec. Anal. Calcd. for C8g22BN2, PF6": C, 3181;

H, 7.34; N, 9.28. Found: C, 31.78; H, 7.40; N, 9.23.

The proton nmr and infrared spectra were identical to

those previously reported.26,27

Synthesis of 2-(2-dimethylaminoethyl) pyridinedinydroboroon

(1+) hexafluorophosphate.


S(1)2 F6
L, (CH2)2 NMe22BH3 (2)NH4PF6 e2 2 6
H2


A sample of 2--(2-dimethylaminoethyl) pyridine-bis(borane)

(1.00 g, 5.64 mmtol) was reacted with solid iodine (0.716 g,







2.~82 mruol), in dry benzene, accordi.r.cg to the cgeieral procedure.

The reaction appeared to be complete within 2 hours. Heating

was continued for an additional 2 hours to ensure complete

reaction. A white solid (yield 1.57 g, 96.3%) was collected.

The iodide salt (1.02 g, 3.51 mmol) was converted to

the hexafluorophosphate salt (yield 1.00 g, 92.6% recovery);

mp 132, lit.26,27 132-133.5. Anal. Calcd. for C9H 14D 2+, PFG-

C, 35.09; H, 5.24; N, 9.10. Found: C, 34.96; H, 5.10; N, 8.95.

The proton nmr and infrared spectra were identical to

those previously reported.26,27

Synthesis of N,N'-dimethylpiperazinedihydroboron (1+)

hexafluorophosphate.


le Me/H2

*2BH3 (l)* f2B2H
(2)NH4P F6
Me

A sample of N,N'-dimethylpiperazine-bis(borane)(1.00 g,

7.04 mmol) was reacted with solid iodine (0.895 g, 3.52 mmol)

in dry benzene, according to the general procedure. The

reaction was heated for 15 hours to ensure complete reaction.

A white solid (yield 1.68 g, 93.9%) was collected.

The iodide salt (1.01 g, 3.98 irmol) was converted to

the hexafluorophosphate salt (yield 0.762 g, 70.8% recovery);

mp 267*, lit.26 265-2670. Anal. Calcd. for C H-6.BN2+ PF6-:

C, 26.49; H, 5.93; N, 10.29. Found: C, 26.47; H, 6.01;

N, 10.20.








The proton nmr and infrared spectra were identical to

those previously reported.26

Synthesis of 2,2'-bipyridyldihydroboron (1+) hexa-

fluorophosphate.


2BH3 2 P6 B2 H
r r't (2)NH A PF6 2 6
H2


A sample of 2,2'-bipyridyl-bis(borane) (0.881 g, 4.79 nuoil)

was reacted with solid iodine (0.611 g, 2.41 mmoi) in

dry benzene, according to the general procedure. The

reaction appeared to be complete within 1 hour, and no

diborane was detectable above the solution after 1.5 hours

of heating. A yellow solid (yield 1.20 g, 84.6%) was collected.

The iodide salt (1.18 g, 3.99 nmmol) was converted to

tec hexafluorophosphate salt (yield 1.05 g, 84.0% recovery);

mp 1.90, dec. lit.25 1700, dec. Anal. Calcd. for

C0Ifl10B24 P6 : C, 38.2; H, 3.18; N, 8.92. Found:

C, 37.9; H, 3.24; N, 8.97.

Proton nmr in CH3CN: three complex multiplets

centered at -7.98 ppm, -8.53 ppm, and -8.83 ppm, with an

intensity ratio of 2:4:2, respectively.

Infrared: doublet centered at 2440 cm-1, assigned to

the B-H stretching mode. Additional absorptions: 3100 (broad),

1680 (s), 1582 (s), 1516 (w), 1489 (s), 1470 (s), 1329 (s),

1171 (s), 1130 (s), 1100 (w), 1080 (s), 1050 (s), 840 (broad,

structured, assigned to PF6) 552 (3) cm-l.







Synthesis of 1,2-(N,il '-bis-piperidine) ethanediJhyd'cro-
boron (1 1 h e:-aflluorcvloophae.



(1)212 7 +
O N(C H 2)2H N 2 (2H6
(2) NHPF + 2
H2

A sample of 1,2-(N,N'-bis-piperidine) ethane-bis(borane)

(1.00 g, 4.69 mmol) was reacted with solid iodine (0.595 g,

2.34 mmol) in dry benzene, according to the general pro--

cedure. The reaction appeared to be complete within 2

hours, and no diborane was detectable above the solution

after 3 hours of heating. A white solid (yield 1.42 g,

93.0%) was collected.

The iodide salt (0.981 g, 3.01 mmol) was converted to

the hexafluorophosphate salt (yield 0.965 g, 93.2% recovery);

mp 1250. Anal. Calcd. for C12H26BN2 PF6 : C, 40.68;

H, 7.34; N, 7.91. Found: C, 40.62; H, 7.44; N, 7.91.

Proton nmr in CH2C12: singlet at -3.41 ppm, and two

complex multiplets centered at -1.73 ppm and -3.06 ppm,

with an intensity ratio of 4:12:8, respectively.
-1
Infrared: doublet centered at 2470 cm-, assigned

to the B-H stretching mode. Additional absorptions:

2960 (s), 1480, 1455, 1340, 1320, 1300, 1255, 1190 (s),

1170, 1155 (s), 1095 (w), 1040 (s), 955, 930, 920, 845
(broad, structured, assigned to P ) 778, 550 (s) cm-
(broad, structured, assigned to PF6-), 778; 550 (s) cm








Synthesis of 2-(2-N-piperidinoethyl)-pyridinedihydro-

boron (1+) hexafluorophosphate.




H2)2 '2BH3 (2)NH4P PF ,H
(R--'2 O__2H


A sample of 2-(2-N-piperidinoethyl)-pyridine-bis(borane)

(1.32 g, 6.03 mmol) was reacted with solid iodine

(0.765 g, 3.01 mrtol) in dry benzene, according to the

Li ir-al procedure. The reaction appeared to be complete

within 1.5 hours, and no diborane was detectable above

the solution after 2 hours of heating. A white solid

(yield 1.80 g, 90.1%) was collected.

The iodide salt (1.50 g, 4.55 minol) was converted to

the hexafluorophosphate salt (yield 1.46 g, 92.4% recovery);

mp 1270. Anal. Calcd. for C, H 2BN PF6: C, 41.38;

H, 5.75; N, 8.05. Found: C, 41.39; H, 5.75; N, 8.03.

Proton nmr in CH2C12: broad singlet with fine structure

at -3.46 ppm, and four complex multiplets centered at

-1.78 ppm, -3.03 ppm, -7.62 ppm and -8.21 ppm, with an

intensity ratio of 4:6:2:2, respectively.

Infrared: strong absorption centered at 2440 cm-I

assigned to the B-H stretching mode. Additional absorptions:

2960 (w), 2385 (w), 1632 (s), 1580, 1505, 1470, 1455 (s),

1435, 1390 (w), 1322, 1313, 1195 (s), 1150 (s), 1120,

1100 (s), 1060, 1040, 1000, 845 (broad, structured,

assigned to PF6-), 790, 770, 550 (s) cm-1








4" ntr,_ .--is 2 (-f 2-(2- -o':,rrolidi;.i th- ) i r i rdro-

boron (1+) hexafluorophosphate.



i (1)I2 2
(CHy) *J2BH3 B PF6 '/2B2H6



A sample of 2-(2-N-pyrrolidinoethyl)pyridine-bis(boraie)

(1.27 g, 6.20 mmol) was reacted with solid iodine (0.788 g,

3.10 rmmol) in dry benzene, according to the general pro-

cedure. The reaction appeared to be complete within 1.5

hours, and no diborane was detectable above the solution

after 2 hours of heating. A white solid (1.76 g, 90.3%)

was collected.

The iodide salt (1.50 g, 4.75 mmol) was converted

to the hexafluorophosphate salt (yield 1.38 g, 87.8% recovery);

mp 1180. Anal. Calcd. for C H11BN2+PF6: C, 39.52;

H, 5.39; N, 8.38. Found: C, 39.49; H, 5.39; N, 8.36.

Proton nmr in CH12C12: broad singlet with fine

structure at -3.49 ppm, and four complex multiplets

centered at -2.15 ppm, -3.17 ppm, -7.67 ppm, and -8.17 ppm,

with an intensity ratio of 4:4:4:2:2, respectively.

Infrared: strong absorption centered at 2450 cm-,

assigned to the B-H stretching mode. Additional absorption:

2990 (w), 2385, 1632 (s), 1580, 1503 (s), 1470, 1459,

1440, 1400 (w), 1340 (w), 1305 (w), 1275, 1260, 1225,

11'"5 160 (s) 1125, 1095, 1020, 845 (broad, structured,

assigned to PF6~, 765 (s), 600 (s) cm-1.
assioned to 6)''









Synthesis of N,N,N',N'-tetramethyl-1,2-propanediaminedi-

hydroboron (1 ) hexafluorophosphate.



e12 2 e $e2 3
Me NCHCH2NM e 2BH3 -> Me2N Me 2B2
(2)NH4PF6
H2


A sample of N,N,N',N'-tetramethyl-1,2-propanediamine-

bis(borane) (1.00 g, 6.33 mmol) was reacted with solid

iodine (0.805 g, 3.16 mmol) in dry benzene, according to

the general procedure. The reaction appeared to be complete

within 1.5 hours, and no diborane was detectable above the

solution after 2 hours of heating. A white solid (yield

1.65 g, 96.2%) was collected.

The iodide salt (0.795 g, 2.94 mmol) was converted to

the hexafluorophosphate salt (yield 0.780 g, 92.0% recovery);

mp 1610 dec. Anal. Calcd. for C7H20BN2'PF6 : C, 29.07;

H, 6.92; N, 9.69. Found: C, 28.95; H, 6.92; N, 9.75.

Proton nmr in CII2C12: doublet centered at -1.34 ppm,

four singlets centered at -2.66 ppm, -2.76 ppm, -2,88 ppm,

and -3.48 ppm, and a complex multiple centered at -3.51

ppm, with an intensity ratio of 3:3:3:6:1:2, re'"c:tively.






Synthesis o J,NH',J' -2-pntanme-yl.-, 3-rcpanediamine-

dil -idrcboropr (+1) he..arfluorophor-phate.


Me e
Ie (1)T r21 PF6
MMe2NCH2CHCH2NMe2,2BH3 --- > Me2N IMe2
(2) NH4PF H2


A sample of N,N,N',N'-2-pentamethyl-l,3-propanediamine-

bis(borane) (1.00 g, 5.81 mmol) was reacted with solid

iodine (0.739 g, 2.91 mmol) in dry benzene, according to

the general procedure. After 2 hours of heating, only a

small amount of solid was present in the reaction flask.

The reaction was heated an additional 12 hours to ensure

completion. A white solid (yield 1.55 g, 93.6%) was

collected. The iodide salt (1.00 g, 3.51 mmol) was

converted to the hexaflaorophosphate salt (yield 0.934 g,

87.8% recovery); mp 1640 dec. Anal. Calcd. for CH 21N 2PF 6

C, 31.89; H, 6.98; N, 9.30. Found: C, 31.72; H, 7.34;

N, 9.26.

Proton nmr in CD3CN: doublet centered at -0.95 ppm,

two intense singlets centered at -2.66 ppm and -2.83 ppm,

covering a complex multiple centered at -2.68 ppm, with

an intensity ratio of 3:6:6:5, respectively.
-l
Infrared: doublet centered at 2460 cm assigned

to the B-H stretching nr.de. Additional absorptions: 2995,

2350, 1500 (s), 1480 (s), 1450 (s) 1420, 1400, 1390,

1345 (s), 1310, 1245 (s), 1215 (s), 1100 (s), 1125, 1105,

1080, 1055, 111.5 (s), 995 (s), 965, 925 (s), 845 (broad,







structured, assigned to PF 6 740, 600 (s) cm 1.

Attempted synthesis of N,N,N',-trimethylethylenediamine-

N (2-trihydroborondimethylaminoethyl)dihydroboron (1+) hexa-

fluorophosphate.


Me filI e/ he PF6 8
Me2 (C2)2N(CH2NMe 2 N M e 3H3 Me ( CH2?BH3 +
S(2) NH4PF6 Y 'Me
12


A sample of pentamethyldiethylenetriamine-tris(borane)

(1.00 g, 4.63 mmol) was reacted with solid iodine (0.586 g,

2.31 mmol) in dry benzene, according to the general pro-

cedure. The reaction was heated for 8 hours to ensure

completion. A white solid (yield 1.20 g, 78.8%) was

collected.

The proton nmr in DO (gas evolution observed)-

singlet at -2.68 ppm, and two complex multiplets centered

at -2.92 ppif and -3.60 ppm, with an intensity ratio of

2.96:12.5:7.5, respectively. The lack of correlation of

the above spectrum suggested a mixture. Addition of solid

K2CO3 to the nmr tube caused considerable change in the

spectrum. A new peak at -2.30 ppm, and a broad singlet

with some fine structure at -2.95 ppm, appeared. Little

change in the multiple at -3.60 ppm was observed. Addition

of a small amount of acid regenerated the initial spectrum.

The above data supports the presence of ammonium salt in

the mixture, believed to be the following:










+2
/ Me Me
Me 2Ne I(CH 2)NH 2PF6
2 -Me
1I2


When the reaction was carried out in CH2C12, rather

than benzene, for a period of 30 hours, a material con-

taining only a trace amount of the ammonium salt was

obtained, as evidenced by the appearance of only a very

small peak in the proton nmr of an alkaline D20 solution.

The iodide salt mixture (0.842 g), from the benzene

procedure, was converted to the hexafluorophosphate salt.

Gas evolution was observed during this conversion (yield

0.810 g, 91.3% recovery); mp 1490. Anal. Calcd. for

C9H28B2N3+, PF6-: C, 31.30; H, 8.12; N, 12.17. Found:
C, 30.32; H, 8.03; N, 12.35. Anal. Calcd. for C9H26BN3+2

2PF6 : C, 22.64; H, 5.45; N, 8.81. The analytical data

suggest a mixture. Attempts to recrystallize the material

failed to improve the analytical data.

Proton nmr in CD3CN: complex system of singlets

centered at -2.60 ppm, -2.68 ppm, -2.85 ppm, -2.87 ppm,

and 3.53 ppm, as well as, a very complex multiple of a

very low intensity, visible from -2.91 ppm to -3.67 ppm.

The above spectrum did not correlate well with the expected,

and provided further evidence of a mixture. However, if

the small singlet at -2.68 ppm was assigned to the ammonium

salt Jim-urity, and combi:-'-d with its borane derivative,








assigned at -2.60 ppm, the resulting intensities of

6:3:6:4:4 correlate well with a mixture of the two described

compounds. From integral ratios it was determined that the

sample contained approximately 87% of the borane salt and

13% ammonium salt. The analytical data of a mixture

of this composition correlates well with the analytical

data obtained on the reaction product. Anal. Calcd. for

mixture: C, 30.17; H, 7.77; N, 12.20. Found: C, 30.32;

H, 8.03; N, 12.35.

A potential separation technique, based on solubility

difference of the (1+) hexafluorophosphate salt was

developed on a microscale, employing proton nmr to confirm

separation. A sample of the impure iodide salt was dissolved

in D20. After gas evolution ceased, a small amount of

solid K2CO3 was added until the pH of the solution was

increased to 10. A small amount of solid KPF6 was added,

and the resulting white solid was removed by centrifuging

the solution. The proton nmr of the remaining solution

revealed two singlets centered at -2.26 ppm and -3.58 ppm,

a broad, structured, intense peak at -2.88 ppm, and a complex

multiple covering the area from -2.50 ppm to -3.33 ppm.

The intensity ratio of 6:4:9:4, respectively, and chemical

shifts were indicative of deprotonated ammonium salt im-

purity. There was no evidence of the borane derivative in

the solution. No attempt was made to isolate this impurity.








Synthesis of N,N,N' trimethylethylenediamine-N' (2-

trihydroboron dimethylaminoethyl)dihydroboron (1+) hexa-

fluorophosphate, via trimethylamine-iodoborane.



Me (1)Me-NB HJX I Me Me PFG
Me2N(CHG)2ti(C H2)2NMe2,3BH3 > Me, N(CH )2BH3 + Me 1 BH3 B2H
(2) NH4PFM
IH2


Trimethylamine-borane (0.810 g, 11.1 mmol), in an Erlen-

meyer flask (200 ml), was dissolved in dry toluene (75 ml).

While continuously stirring the solution, solid iodine

(1.40 g, 5.55 mmol) was added. After gas evolution had

ceased, and the solution had become colorless, pentamethyl-

diethylenetriamine-tris(borane) (2.00 g, 9.30 mmol) was

added. Reaction was continued according to the general

procedure. The mixture was heated at 900 for 18 hours to

ensure completion. A white solid (yield 2.95 g, 97%) was

collected. The toluene solution, containing trimethylamine-

borane, could be reused for additional reactions.

The proton nmr in alkaline D20, revealed the absence

of any ammonium salt. The iodide salt (1.79 g, 5.47 mmol)

was converted to the hexafluorophosphate salt (yield 1.69 g,

89.5% recovery); mp 158-1590. Anal. Calcd. for C9H28B2N3+'

PF6-: C, 31.30; H, 8.12; N, 12.17. Found: C, 31.34;

H, 8.20; N, 12.17.

Proton nmr in CH3CN: four singlets centered at

-2.60 ppm, -2.82 ppm, -2.86 ppm, and -3.51 ppm, and a com-

plex multiple of low intensity, covering the area from







-2.50 ppm to -3.33 ppm, with an intensity ratio of 6:3:6:4:4,

respectively. 11B nmr in CH3CN: quartet at 28.8 ppm

and triplet at 13.7 ppra from trimethylborate. The B-H

coupling constants were approximately 96 Hz and 108 Hz,

respectively.

Infrared: complex absorption band covering the

region from 2280 to 2518 cm-1, assigned to B-H stretching

modes of both BH2+ and BH3 entities. Additional absorptions:

1.487 (s), 1470, 1465, 1460, 1445, 1325 (w), 1290 (w),

1252, 1220, 1205, 1173 (s), 1020 (s), 1000 (s), 960, 845

(broad, structured, assigned to PF6-), 550 (s) cm-1.

The presence of the BH3 functionality was confirmed

by reaction of the iodide salt dissolved in D20, with

iodine. The proton nmr was monitored for one hour, during

which time the singlet assigned to the dimethylanino-

borane group diminished in intensity, until it was totally

absent from the spectrum. At the same time, a sharp new

singlet appeared 19Hz downfield from the disappearing

singlet, indicative of the formation of the ammonium ion.

No attempt was made to isolate this material.

Synthesis of the cyclic boronium cation of N-methyl-

N'-(2-dimethylaminoethyl)piperazine.




Me NMe2- 3BH3 ()2 MN Me P + ." H
\ H)2Nh 3H(2)NH4PF6 BIH3 \_ 'y
12







A sample of N-methyl-N'-(2-dimethylaminoethyl) piperazine-

tris(borane) (2.00 g, 9.39 mmol) was reacted with solid

iodine (1.19 g, 4.70 mmol) in dry benzene, according to

the general procedure. The mixture was heated for 3

hours, at which time no diborane was detectable above

the solution. A white solid (yield 2.75 g, 89.8%) was col-

lected.

The proton nmr of the iodide salt in D20, with TMSP

as an internal reference, revealed a complex spectrum

consisting of two singlets centered at -2.80 ppm and

-2.92 ppm, and two complex multiplets centered at -3.18 ppm

and -3.66 ppm, with an intensity ratio of 3:6:4:8, respectively.

It was observed that during the determination of this

spectrum, a new peak centered at -2.53 ppm was appearing,

suggesting hydrolysis of the BH3 group.

The iodide salt (1.01 g, 3.09 mmol) was converted to

the hexafluorophosphate salt (yield 0.954 g, 98.7% recovery);

mp 184-1850. Anal. Calcd. for C9H26B2N3 PF6-: C, 31.48;

H, 7.58; N, 12.24. Found: C, 31.29; H, 7.59; N, 12.16.

Proton nmr in CD3CN: complex spectrum consisting

of two singlets centered at -2.63 ppm and -2.85 ppm, and

two complex multiplets centered at -3.08 ppm and -3.52 ppm,

with an intensity ratio of 3:6:4:8, respectively.

Infrared: complex absorption band covering the region

from 2300 to 2520 cm-1, assigned to B-H stretching modes of

both BH 2 and H-3 entities. Additional absorption:








1475 (broad, structured), 1360, 1350, 1315, 1260 (w),

1210 (s), 1165 (s), 1145, 1110, 1040 (w), 1010, 995,

978 (w), 950 (broad, structured), 845 (broad, structured,

assigned to PF6 ), 550 (s) cm-1

Synthesis of 2,2'-dipyridylmethanedihydroboron (1+)

hexafluorophosphate, via trimethylamine-iodoborane.



2 1.2BH3 / Nj B l PFe t+ BH + M1j3NH3
( 2 ) N H 4 6
N2

Trimethylamine-borane (1.01 g, 13.8 mmol), in an Erien-

meyer flask, was dissolved in dry benzene (75 ml). While

continuously stirring the solution, solid iodine (1.75 g,

6.89 mmol) was added. After gas evolution had ceased,

and the solution had become colorless, 2,2'-dipyridylmethane-

bis(borane) (2.70 g, 13.8 mmol) was added. The reaction

mixture was heated just below reflux for 18 hours, and

diborane was removed under nitrogen. A white solid

(yield 3.55 g, 83.0%) was collected.

The iodide salt (1.50 g, 4.84 rnmol) was converted to

the hexafluorophosphate salt (yield 1.45 g, 91.4%); mp

1960, dec..

The proton nmr and infrared spectra were identical

to those of an authentic sample.







Reaction of 2,2'-dipyridylmethane with trimethylamine-

iodoborane.



I + Me3NBH21



To a solution of trimethylamine-iodoborane, prepared by

adding iodine (1.49 g, 5.87 mmol) to trimethylamine-borane

(0.859 g, 11.8 mmol) dissolved in dry benzene (80 ml),

was added 2,2'-dipyridylmethane (2.00 g, 11.8 mmol), with

continuous stirring. The solution turned red-orange

in color almost immediately.

The solution was refluxed for 80 hours, during which

time a stream of nitrogen gas was passed above the reaction

solution to remove liberated trimethylamine. The presence

of trimethylamine was indicated by its reaction with moist

litmus paper. The resulting orange solid was removed by

vacuum-filtration, and vacuum-dried (yield 3.40 g, 92.9%).

Proton nmr in CH2C12: mixture of materials, as evi-

denced by three singlets at -2.66 ppm, -2.80 ppm, and -3.00

ppm, assigned to non-coupling methyl groups.

All attempts to isolate a pure, boron-containing material

were unsuccessful. It is postulated that two of the materials

present are the anhydro base of 2,2'-dipyridylmethane dihydro-

boron cation, which gives rise to the intense red-orange

color, and the ammonium salt of trimethylamine.





61
Attempted reaction of NN,N',N'-tetramnethylhexanediamrine-

bis (borane) with iodine.


Me2N(CH2)6NMe2.2BH3 -2 No Reaction



A sample of N,N,,N'N'-tetramethylhexanediamine-bis(borane)

(2.02 g, 10.1 mmol) was reacted with solid iodine (1.28 g,

5.03 mmol) in dry mesitylene, according to the general

procedure. The mixture was refluxed for 4 weeks without

production of any cationic material.

Attempted reaction of trimethylamine-borane with

trimethylamine-iodoborane in benzene.



Me3NBH3 + Me3NBH2L H No Reaction


To a sample of trimethylamine-iodoborane (1.00 g, 5.03 mmol)

in dry benzene (50 ml), prepared by the reaction of tri-

methylamine-borane (0.367 g, 5.03 mmol) and iodine (0.638 g,

2.51 nmmol), was added trimethylamine-borane (0.367 g, 5.03

mmol). The mixture was refluxed for 30 hours with no visible

evidence of diborane evolution, or reaction. The proton

nmr of the solution revealed only the presence of starting

materials.

Attempted reaction of trimethylamine-borane with tri-

imethylan :in.e-iodoborane neat.


Me3NBH3 + Me3NBH2I --> No Reaction


To a sample of trimethylamine-iodoborane (1.00 g, 5.03 mmol)








in a reaction flask (50 ml), prepared by the reaction

described previously, was added trimethylamine-borane

(0.367 g, 5.03 mmol). The reaction flask was connected

to a vacuum line, purged, and sealed. The mixture was

heated as a melt in an oil bath for 3 hours, cooled, and

opened to the vacuum line. No gaseous material was

observed. The proton nmr in CH2C12 revealed only unchanged

starting materials.

Synthesis of Cyclic Boronium Cations by Methods
other than Reactions of Polyamine-Boranes with
Iodine or Trimethylamine-Iodoborane

Synthesis of 2(-trihydroborondimethylaminomethyl)-N-

methyl pyridinium (1+) hexafluorophosphate.



Mmes --^ PF Me 6PF
CH2 BH3 (2) NH4PF6 CH H3
H2 Me


To a sample of 2(-trihydroborondimethylaminomethyl)pyridine:

(1.00 g, 6.66 mmol), in an Erienmeyer flask (125 ml), was

added dry benzene (70 ml). While continuously stirring

the solution, methyl fluorosulfonate (0.759 g, 6.66 mmol)

was added. The solution was allowed to stir for 8 hours to

ensure complete reaction. A white solid (yield 1.58 g,

89.8%) was filtered from the solution, washed with two

portions (50 ml) of diethyl ether, and vacuum-dried.

Conversion to the hexafluorophosphate salt was

accomplished by dissolving the fluorosulfonate salt








(1.58 g, 5.98 mmol) in H20 (20 ml), and adding 5M :H4 PF6

(2 mJ). The mixture was cooled in an ice bath, vacuum-

filtered, washed with ice cold water (30 ml), three

portions (50 ml) of dry ether, and vacuum-dried (yield

1.80 g, 97.1% recovery).

Proton nmr in CD3CN: five singlets, and a large

complex multiple extending from -7.75 ppm to -9.10 ppm.

The lack of correlation of this spectrum to that expected,

suggested a mixture, thought to be that of the desired

compound, and approximately 20% of the cyclic boronium

cation. Separation was accomplished by washing the salt

with three portions (15 ml) of CH2C12, which removed what

was latter identified to be the cyclic boronium cation.

Proton nmr of the remaining solid (1.40 g, 75.5%

overall yield) in CD CN: three singlets centered at

-2.78 ppm, -4.38 ppm, and -4.58 ppm, and three complex

multiplets centered at -8.08 ppm, -8.48 ppm, and -8.75 ppm,

with an intensity ratio of 6:2:3:2:1:1, respectively.

Infrared: strong absorption, centered at 2390 cm-1

assigned to B-H stretching mode. Additional absorption:

3100, "3125, 3080, 1640 (s), 1595 (s), 1529, 1490, 1472 (s),

1452, 1420, 1385, 1350, 1315, 1280, 1242, 3210, 1175 (s),

1160 (s), 1025 (s), 1010 (s), 955 (s), 845 (broad, structured,

assigned to PFg-), 550 (s) cm-.

The above data correlates well with the expected

product. Anal. Calcd. for C9HIEB2+PF6-: C, 34.84;








H, 5.81; N, 9.03, Found: C, 34.96; H, 5.79; N; 9.03;

mp 1200.

The proton nmr spectrum of the CH2C12 soluble impurity

was found to be identical to that of the cyclic boronium

cation (I).


1 >Me ^6PF
LMe 2e
T A2


Synthesis of 2(-dimethylaminometh l)pyridinedihydro-

boron (1+) hexafluorophosphate, via 4-methylpyridine-

iodoborane.

0e (1) 4-MePyBH21, PF-
Me NMe2o + 4-MePyBH3
CH^ BH3 (2) NH4PF6 2/
H2

A sample of 4-methylpyridine-borane (0.357 g, 3.33 mmol),

in an Erlenmeyer flask (125 ml), was dissolved in dry

CH2C12 (30 ml). While continuously stirring the solution,

solid iodine (0.421 g, 1.66 mmol) was added. After the

iodine color was discharged, and no further gas evolution

was observed, 2(-trihydroborondimethylaminomethyl)pyridine

(0.500 g, 3.33 mmol) was added. The solution was stirred

constantly for 3 hours, during which time diborane was

observed above the solution. Dry diethyl ether (100 ml)

was add-jd to the reaction flask. A white solid precipitated,

and was removed by filtration, washed with two portions (50 ml)

of dry diethyl ether, and vacuum-dried (yield 0.810 g,

84.9% yield).








Conversion to the hexafluorophosphate salt was accom-

plished by dissolving the iodide salt (0.810 g, 2.83 mmol)

in H20 (20 ml), and adding 5M NH4PF6 (2 ml). The mixture

was cooled in an ice bath, vacuum-filtered, washed with

ice cold water (30 ml), three portions (50 ml) of dry

diethyl ether, and vacuum-dried (yield 0.790 g, 95.0%

recovery); mp 122-123.

The proton nmr and infrared spectra were identical to

those of an authentic sample.

Synthesis of 2(-dimethylaminomethyl)pyridinedihydroborn

(1+) hexafluorophosphate, via tritylchloride.



| Me (I)3CCI i() 'Ce2 I PF6
J CH _NBH3 (2) NH4PF6
'N I2 e H


A sample of 2-(trihydroborondimethylaminomethyl)pyridine

(0.750 g, 5.00 mmol), in an Erlenmeyer flask (125 ml),

was dissolved in dry CH2C12 (30 ml). To this solution

was added tritylchloride (1.39 g, 5.00 mmol). The solution

was refluxed for 24 hours to ensure complete reaction.

The CH2C12 was removed under vacuum and the resulting

white solid was washed with two portions (50 ml) of dry

ether.

Conversion to the hexafluorophosphate salt was accom-

plished by dissolving the crude iodide salt in HO (20 ml),

and adding 5M NH4PF6 (2 ml). The mixture was cooled in

an ice bath, vacuum-filtered, washed with ice cold water

(30 ml), three portions (50 ml) of dry ether, and vacuum-







dried (yield 1.14 g, 73.5%); mp 122-1230. Anal. Calcd.

for CH4 BN2PF6: C, 32.65; H, 4.76; N, 9.52. Found:

C, 32.67; H, 4.80; N, 9.51.

Proton nmr in CH2C12: two singlets centered at -2.96

ppm and -4.71 ppm, and three complex multiplets centered at

-7.83 ppm, -8.30 ppm, and -8.50 ppm, with an intensity

ratio of 6:2:2:1:1, respectively.
-1
Infrared: doublet centered at 2474 cm assigned to

B-H stretching mode. Additional absorptions: 2391 (s),

1640 (s), 1500 (s), 1485, 1470 (s), 1420, 1390, 1365,

1307 (s), 1280, 1250, 1207 (s), 1170, 1152, 1132, 1120,

1110, 1090 (s), 1030, 1000 (s), 970, 910 (s), 845 (broad,

structured, assigned to PF6-), 780, 760, 710, and 550 cm-1

Reactions and Derivatives of
2,2'-Dipyridylmethanedihydroboron (1+) Salts

Synthesis of the anhydro base of 2,2'-dipyridylnmethane-

dihydroboron (1+) iodide.



.-" NoOH

H2 H2

A sample of 2,2'-dipyridylmethanedihydroboron (1+) iodide,

(2.00 g, 6.48 mmol) was dissolved in water (28 ml). The

solution was cooled in an ice bath while being stirred

continuously. To this cooled solution was added 2N ifO!

(6 ml), which produced a deep red-orange solution initially,

and finally an orange precipitate.








The precipitate was removed by vacuum-filtration, washed

with cold water (20 ml), and vacuum-dried (yield 1.08 g,

91.6%); mp 83-840. Anal. Calcd. for C11H11N2B: C, 72.52;

H, 6.04; N, 15.39. Found: C, 72.47; H, 6.10; N, 15.37;

B, 6.06. The material was hydroscopic and appeared to be

unstable on prolonged exposure to air. For these reasons,

the sample was stored under vacuum in a dry box.

A sample of the orange solid was placed in a vacuum

sublimator, and heated in an oil bath at 700C, under a

pressure of 10-3torr. The rate of sublimation was very

slow and did not afford a reasonable means of recovery,

due to decomposition under prolonged heating.

Proton nmr in CCi4: sharp singlet centered at

--4.93 ppm, and three complex multiplets centered at -6.28

ppm, -6.97 ppm, and -7.30 ppm, with an intensity ratio

of 1:4:2:2, respectively. 11B nmr in CH2C12: triplet

centered at 22.9 ppm from trimethylborate. The B-H

coupling constant was approximately 100 Hz.

Infrared; strong absorption, centered at 2450 cm-1

assigned to B-H stretching mode. Additional absorption:

2280, 2222, 1625 (s), 1560 (s), 1550, 1482 (s), 1463 (s),

1395, 1335, 1285 (w), 1190 (s), 1182, 1121, 1105, 1060,

1049, 1030, 991, 980, 979, 972, 955, 905, 878, 770 (s), 750,

721, 715, 598 cm-1








Synthesis of 2,2-(2,2'-dipyridyldihydroboron)propane

(1+) hexafluorophosphate.


(Me)
Me N NMe 1 2


H2

A sample of 2,2'-dipyridylmethanedihydroboron (1+) iodide

(1.00 g, 3.23 mmol), in an Erlenmeyer flask (50 ml), was

reacted with methyl iodide (10 ml), and bis-l,8-dimethyl-

aminonaphthalene (1.40 g, 6.54 mmol). The orange-red solu-

tion was stirred continuously for 20 hours. The resulting

solid was removed by vacuum-filtration, and washed with

diethyl ether (50 ml). This solid was suspended in H20,

and the pH increased to approximately 8 with K2CO3. The

remaining insoluble material (bis-l,8-dimethylaminonaphthalene

ammonium (1+) iodide) was removed by filtration. The pH

of the remaining aqueous solution was increased to approx-

imately 10, giving rise to an orange color, and extracted

with two portions (50 ml) of CH2Cl2. The pH of the solution

was decreased to approximately 4 by the addition of 2N HC1,

and 5M NH4PF, (2 ml) was added. The solution was cooled

in an ice bath, and the white solid removed by filtration,

washed with ice cold water (20 ml), diethyl ether (50 ml),

and vacuum-dried (yield 0.987 g, 85.8%); mp 237. Anal.

Calcd. for C13Hl6BN2+PF6-: C, 43.82; H, 4.49; N, 7.87.

Found: C, 43.76; H, 4.54; N, 7.92.







Proton nmr in DISO-D6: sharp singlet at -1.93 ppm

and three complex multiplets centered at -7.99 ppm, -8.50

ppm, -8.97 ppm, with an intensity ratio of 6:2:4:2, re-

spectively.
-1
Infrared: strong absorption centered at 2460 cm ,

assigned to B-H stretching mode. Additional absorptions:

1625 (s), 1590 (s), 1495 (s), 1453, 1405, 1375, 1319,

1270, 1170 (s), 1100, 1060, 1005, 845 (broad, structured,
-1
assigned to PF6-), 780 (s), 550 (s) cm-.

Protonation of the anhydro base derived from 2,2'-

-dipyridylmethanedihydroboron cation.


(1) YHC
(2) NH4PF6 IPF6
H2 H2

To a sample of the anhydro base of 2,2'-dipyridylmethane-

dihydroboron cation (0.244 g, 1.34 mmol), suspended in

water (30 m3), was added 2N HC1, until a pH of approximately

2 was obtained. To the pale green solution was added

5M NII4PF6 (4 ml). The resulting white solid was removed

by filtration, washed with diethyl ether, and vacuum-

dried (yield 0.380 g, 86.5%); mp 1940.

The proton nmr and infrared spectra were identical

to those of an authentic sample.







Sy1gthesis of the deuterated anhydro base of 2,2'-

-dipyridylmethanedihydroboron (I ') iodide.



(1) D
(2) K2C03 -
H2 H2


A sample of 2,2'-dipyridylmethanedihydroboron (1+) iodide

(1.00 g, 3.23 mmol), in an Erlenmeyer flask (50 ml), was dis-

solved in DO0 (99%, 20 ml). The pH of the solution was ad-

justed to approximately 8 with K2CO3. The solution was

stirred for 30 minutes, at which time the pH was increased

to 10 with additional K2CO3. The resulting orange solid was

removed by filtration, washed with ice cold D20 (5 ml), and

vacuum-dried (yield 0.550 g, 93.6%).

The proton nmr in CCl4 was identical to that of an

authentic sample, except for considerable reduction of the

singlet at -4.93 ppm, assigned to the lone methylene proton,

which has undergone an exchange reaction with D20. From the

relative intensities, the sample appeared to be approximately

85% deuterated.

The infrared spectrum revealed an increase in inten-

sities of the following absorptions: 1060, 979, 972, 955,

and a new peak at 520 cm-1
and a new peak at 520 cm.








Attempted synthesis of 1,1-(2,2'-dipyridyldihydroboron)

ethane (1 ) hexafluorophosphate.


Me
(1) )MeSQ^F P T(
2) NH4P I--,
H2 H2

A sample of the anhydro base of 2,2'-dipyridylmethanedi-

hydroboron cation (0.650 g, 3.57 mmol), in an Erlenmeyer

flask (50 ml), was dissolved in CH2C12 (30 ml), in a dry

box. To this continuously stirred solution was added

methyl fluorosulfonate (1.40 g, 12.3 mmol). After approx-

imately 10 minutes, the initial orange solution had

become a pale yellow. The volatiles were removed under

vacuum, and water (30 ml) was added to the remaining

yellow solid. The aqueous solution was filtered, and

5M NH4PF6 (3 ml) was a.dJc-d. The resulting pale yellow

solid was washed with ice cold water (20 ml), and vacuum-

dried (yield 1.10 g, 89.8% recovery).

Proton nmr in CH2C12: doublet at -1.95 ppm

(JC- 7Hz) two small singlets at -1.97 ppm and -4.72 ppm,

and three complex multiplets centered at -7.85 ppm, -8.35

ppm, and -8.6S ppm. The spectrum clearly indicated the

presence of a mixture consisting of the moncmethyl

dimethyl, and unsubstituted cations. From the integral

ratios, the percent composition was approximately 94%,

3%, and 3%, respectively.






Separation of the dimethyl cation was accomplished

by suspending the mixture in ice cold water (20 ml), and

adjusting the pH to approximately 10. After approximately

10 minutes of stirring, the red-orange precipitate was re-

moved by vacuum-filtration, washed with ice cold water

(20 ml), redissolved in 0.1N HC1 (10 ml), and precipitated

as the hexafluorophosphate salt by the addition of

5M NH4PF6 (2 ml). The resulting white solid was washed

with ice cold water (10 ml), and vacuum-dried. The

proton nmr in CH2C12, revealed a mixture containing only

the monoethyl and unsubstituted cations. No further

attempts were made to separate these cations.

Reaction of the anhydro base of 2,2'-dipyridylmethanedi-

hydroboron cation with methyl iodide.




SMe > Mixture of Cations

H2


A sample of the anhydro base of 2,2'-dipyridylmethanedi-

hydroboron cation (0.432 g, 2.37 mmol), in an Erlenmeyer

flask (50 ml), was dissolved in CH3I (30 ml). The deep

red-orange solution was stirred continuously until the

color was discharged, approximately 72 hours. The volatiles

were removed under vacuum, and the remaining solid was

dissolved in CH2-C2, filtered, precipitated with hexane,

filtered, and vacuum-dried (yield 0.728 g, 94.8%).







Conversion to the hexafluorophosphate salt was

accomplished by dissolving the iodide salt in water (25 ml),

and adding 5M NH4PF6 (3 ml). The solution was cooled in

an ice bath, filtered, washed with ice cold water (20 ml),

and vacuum-dried (yield 0.690 g, 85.1% recovery).

The proton nmr in CH2C12 revealed a mixture containing

the monomethyl, dimethyl, and unsubstituted cations. From

the integral ratios, the mixture was determined to be

approximately 80% monomethyl cation, 10% dimethyl cation,

and 10% unsubstituted cation. Separation from the dimethyl

cation was achieved by the addition of base, filtration of

the insoluble anhydro bases of the monomethyl and unsub-

stituted cations, acidification of these anhydro bases,

and conversion to their hexafluorophosphate salts.

Attempts to separate the monomethyl and unsubstituted

cations from one another were unsuccessful.

Reaction of 2,2'-dipyridylmethanedihydroboron (1)

iodide, with methyl iodide, and potassium carbonate.


Me
-r -I (1) K2C03+MeI f II^ PF-
(2) NH4PF%
H2 H2


To a sample of 2,2'-dipyridylmethanedihydroboron (1+)

iodide (0.502 g, 1.62 mmol), in an Erlenmeyer flask

(50 ml), was added CH3CN (30 ml), CH I (5 ml), and

anhydrous K2CO3 (0.566 g, 4.07 mmol). The red-orange

mixture was heated at 400 for 18 hours, with continuous






stirring. The volatiles were removed under vacuum, and

the resulting solid was acidified with lN HC1 until all

gas evolution had ceased. The addition of 54 NH4PF6

(3 ml) produced a white solid which was removed by vacuum-

filtration and vacuum-dried (yield 0.501 g, 86.8% recovery).

The proton nmr in CH2Cl2 revealed a mixture of the

monosubstituted, disubstituted, and unsubstituted cations.

The predominant material was that of the disubstituted

cation. No attempts were made to separate the mixture.

However, employment of long reaction times should pro-

vide a pure product.

Reaction of the anhydro base of 2,2'-dipyridylmethanedi-

hydroboron cation with tritylperchlorate.




+I + C I
H2


A sample of the anhydro base of 2,2'-dipyridylmethanedi-

hydroboron cation (0.500 g, 2.75 mmol), in an Erlenmeyer

flas. (50 ml), was dissolved in dry benzene (30 ml) in a

dry box. To this solution was added freshly prepared, dry

tritylyperchlorate (0.943 g, 2.75 mmol). The red-orange

solution lightened and it appeared as if a new solid was

formed. The solution was stirred for 14 hours and filtered.

iTh red-orange solid was washed with dry benzene (10 ml),

and vacuum-dried (yield 0.983 g, 129% of theoretical).








The combined benzene solutions were evaporated to

dryness, and a solid material (0.685 g) was recovered.

The proton nmr of this material confirmed its identity as

tritylmethane (yield 102%).

Several attempts to isolate and characterize other

reaction products were unsuccessful, and the lack of

solubility of reaction products in solvents that would

not react, made purification virtually impossible. The

isolation and identification of tritylmethane does pro-

vide evidence that hydride abstraction did occur, and

that a new boron-containing material does exist.

The yields of both the iodide salts, hexafluoro-

phosphate salts, overall yields of hexafluorophosphate

salts, anhydro bases, and melting points of all compounds

contained in this chapter appear in Table III.










Table III


Yields and Melting Points of Cations and Derivatives

Compound Yield % I- PF a b Mp C Lit


I+


H2
m4 Me2


A2


99.3 94.1 93.4


95.4 92.3 88.1



95.3 81.3 77.5


196


245 240-244c'd



243 241-245d,e


90.8 66.7 60.6


Me BNMe
F42


250 230-21 d,e


H2





i42


142
rt4


96.3



93.9


92.6 89.2



70.8 66.5


84.6 84.0 77.1


132 132-133,e



267 265-267e



189 170C


93.1 93.2 86.7


125












Table III(continued)


Compound Yields % Ir PF6 PF MpO Lit


90.1 92.4 88.3 127




90.3 87.8 72.3 118



96.2 92.0 88.5 161




93.6 87.8 82.2 164


,Me
M Me-
i2

Me

M QMe
!2


--e Me
Me NCCH2)2NBH3
2 Me
H2




r2


,B4t 1 NB2Me2
Bt.^-7 fi


97.0 89.5 86.8 158-159




84.9 95.0 80.7 122-123


89.8 98.7 88.6


184-185


-- -- 75.5


?42


120











Table III (continued)

Compound Yield % I PF a PF b Mp C Lit

h e

| 1 I |mixture of products ---
H2
MeMe

SPF6-- -- 858 237
H2

91.6 ---- ----- 83-84

H2

percent recovered from iodide salt;b Overall yield;
c N. E. Miller and E. L. Muetterties, J. Am. Chem. Soc.,
86, 1033(1964); d T. E. Sullivan, Doctoral Dissertation,
University of Florida, (1970); e G. E. Ryschkewitsch and
T. E. Sullivan. Inorg. Chem., 3, 899(1970);












CHAPTER VI

PHYSICAL MEASUREMENTS


Acid-Base Dissociation Constant Determination Using
Electronic Spectra

The reactions of the red-orange, aqueous solution of

the anhydro base of the cyclic boronium cation derived

from 2,2'-dipyridylmethane, with acid, produced a color-

less solution, suggesting the use of a colorimetric

method to determine the acid dissociation constant.


S__


H2 H2

The spectra for each compound was obtained with a Beckman

DB recording spectrophotometer, using Icm square, fused-

silica cells. The equilibrium was shifted to both

extremes with 0.10M HC1 to observe the protonated com-

pound, and with 0.10M NaOH to observe the unprotonated

compound. It was found that the protonated compound

failed to show any absorption in the 600-300 (nm) region,

while the deprctonated compound revealed several absorptions

in this region (see fig. I), and it was possible, by care-

fully monitoring the pH of the solution, to determine

the Ka of the acid-base conjugate pairs.

Employing the method described by Deutsch and Taube,31







and by assuming that as the pH is lowered the unprotonated

form is converted to the protonated form, the following

relationship applies.

r iOBS H
Ka = H](EX E, L
Ka=
OBS NEUT
(E EK )


Where [H+] is the hydronium ion concentration, EkOBS is

the extinction coefficient observed at wavelength of the

intermediate pH solutions, EXH is the extinction coefficient

observed at wavelength A. of the completely protonated form,

and EXNEUT is the extinction coefficient observed at

wavelength of the completely unprotonated form. The

pH of the intermediate solutions was kept constant by

employing suitable buffers, and care was taken to choose a

wavelength to monitor that was not affected by the absorp-

tions of the buffers.32 Only those pH's where the trans-

mittance fell in the middle 60% range of the total

difference between the completely protonated and com-

pletely unprotonated forms were used in the calculations

of the Ka, and the pH of the buffered solutions was checked

with a Corning 12 Research pH meter, using the expanded

scale. In this study it was imperative that all solutions

be oxygen-free, due to what appeared to be a decomposition

of the material in alkaline solution when oxygen was

present.








By taking the spectrum at every pH unit from 7 to 12,

the pH range was found where significant quantities of

both acid and base are in equilibrium. The spectra of

those solutions whose pH varied approximately 0.13 of a

pH unit within this range were taken against a buffer

solution reference, and extinction coefficients were

calculated. From the extinction coefficients and the pH

of the solutions, the Ka was obtained. The total con-

centration of the absorbing species, wavelength monitored,

data obtained, and calculated Ka's, are listed in Table IV.

Infrared Spectra

The infrared spectra were obtained from KBr pellets,

using the Beckman IR-10, or the Perkin-Elmer 137 instrument.

The detailed infrared data of all compounds not previously

reported, were included with their synthesis in Chapters

III-V.

Infrared was used in this study only as a tool to

characterize the presence of certain functional groups

(i.e., BH2 BH3, OH), and detailed analyses of the

spectra were not performed. In the case of the polyamine-

boranes, and boron cations, the spectra are similar to

those reported in the literature.25,30,33,34 Several

detailed discussions of the spectra of amine-boranes and

boron cations have been reported,4'27,28 and are consistent

with the findings in this study.








Nuclear Magnetic Resonance Spectra

Proton nmr spectra of materials reported in this study

were obtained on the Varian-A60 instrument, with tetra-

methylsilane (TMS) as an internal reference. The sodium

salt of tetramethylsilylpropinate (TMSP) was used as an

internal reference with D20. In most cases, methylene

chloride or acetonitrile were the solvents of choice, but

occasionally other solvents, such as nitromethane, or

D20, were used in order to obtain more highly resolved

spectra, when the compound was found to be less soluble

in methylene chloride or acetronitrile. The chemical

shifts,$ in parts per million, and coupling constants,

J, in Hertz, of proton resonances and boron resonances

are reported in Tables V-VIII. The integrated intensities

of the proton spectra of the compounds reported, agreed

well with the expected values, and thus, nmr proved to

be an extremely useful tool for characterization of the

comDou.:ids prepared in this study.



























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