• TABLE OF CONTENTS
HIDE
 Title Page
 Acknowledgement
 Table of Contents
 List of Tables
 List of Figures
 Part I: Mechanism of dehydrogenation...
 Part II: Synthesis of trimethylamine...
 Summary
 Bibliography
 Biographical sketch














Title: Reactions of amine boranes and related compounds: (I) Mechanism of dehydrogenation of dimethylamine borane (II) Synthesis of trimethylamine chloroboranes
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 Material Information
Title: Reactions of amine boranes and related compounds: (I) Mechanism of dehydrogenation of dimethylamine borane (II) Synthesis of trimethylamine chloroboranes
Alternate Title: Amine boranes and related compounds, Reactions of
Physical Description: xi, 178 l. : illus. ; 28 cm.
Language: English
Creator: Wiggins, James William, 1940-
Publisher: s.n.
Place of Publication: Gainesville
Publication Date: 1966
Copyright Date: 1966
 Subjects
Subject: Borane   ( lcsh )
Amines   ( lcsh )
Chemistry thesis Ph. D
Dissertations, Academic -- Chemistry -- UF
Genre: bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Thesis: Thesis - University of Florida.
Bibliography: Bibliography: l. 175-177.
Additional Physical Form: Also available on World Wide Web
General Note: Manuscript copy.
General Note: Vita.
 Record Information
Bibliographic ID: UF00097887
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: alephbibnum - 000424000
oclc - 11062888
notis - ACH2405

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Table of Contents
    Title Page
        Page i
        Page i-a
    Acknowledgement
        Page ii
        Page iii
    Table of Contents
        Page iv
        Page v
        Page vi
        Page vii
    List of Tables
        Page viii
        Page ix
    List of Figures
        Page x
        Page xi
    Part I: Mechanism of dehydrogenation of dimethylamine borane
        Page 1
        Page 2
        Page 3
        Page 4
        Page 5
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    Part II: Synthesis of trimethylamine chloroboranes
        Page 92
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    Summary
        Page 173
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    Bibliography
        Page 175
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    Biographical sketch
        Page 178
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Full Text












REACTIONS OF AMINE BORANES AND
RELATED COMPOUNDS:
(I) MECHANISM OF DEHYDROGENATION
OF DIMETHYLAMINE BORANE
(II) SYNTHESIS OF TRIMETHYLAMINE
CHLOROBORANES







By
JAMES WILLIAM WIGGINS


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








UNIVERSITY OF FLORIDA


December, 1966











ACIKNOWLEDGMENTS


I acknowledge with sincere gratitude the assistance

given by the Chairman of my supervisory committee, Dr. G. E.

Ryschkewitsch, during the preparation of this work. His

enthusiasm and patient instruction during the course of the

research made the work a pleasure. The decisive influence

and interest in my professional career of Dr. Ryschkewitsch

has been deeply appreciated.

I sincerely thank the members of my supervisory com-

mittee and the many other faculty members who have expressed

an interest in my growth as a chemist.

I express my thanks for financial support to the

National Science Foundation Grant G19738 and the Chemistry

Department for support on the Science Development Grant.

I thank Mr. D. D. Davis and Dr. Alan Hagopian for

obtaining the mass spectra. I thank Dr. Wallace S. Brey,

Jr., and Dr. K. N. Scott for obtaining the B1 nuclear

magnetic resonance spectra.

A special thanks is extended to Mr. R. G. Logsdon

for building and repairing the glass vacuum system used in

the work.

I thank Mrs. Thyra Johnston for typing the final copy

of the dissertation.










The many enlightening discussions and endeavors

with Dr. Gerhard M. Schmid have made my work toward the

Ph.D. degree a real joy.


iii










TABLE OF CONTENTS

Page
ACKNOWLEDGMENTS . . . . . . . . ii

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

LIST OF FIGURES . . . . . . . . .. x
PART I. MECHANISM OF DEHYDROGENATION OF
DIMETHYLAMINE BORANE

INTRODUCTION. . . . . . . .. . . 1

EXPERIMENTAL .. ............ . . 3

Nomenclature . . a . . . . . 3
Origin of reagents . .. . . ... . 3
Purification of reagents . . . . 3
Instruments. . . . . . . ... 4
General method for the analysis of the
dimethylamine boranes ............ 5
Pyrolysis of B2D6. . . . . . . .. 6
Infrared spectral analysis .......... 8
Mass spectral analysis ... ..... 19
Preparation of (CH ) NBD3 from (CH )3NBHk in an
acidic Dp2solution .. . . . . . . 26
Preparation of B2D6 from (CH )3NBD3 and BF3(g) . 29
Variation in the per cent reaction of (CH3)3NBH3
and B F3(g) to yield B26 . . . . . .. 32
Preparation of B2D6 from NaBD4 and BF3(g) in
diglyme . . . .6 . . . . 36
Preparation of B2H6 from NaBH and BF3(g) in
diglyme . . . . . . . . . . 38
General procedure for preparation of (CH )2ND. . 39
General method for the preparation of (CH )2HNBH3
from B2H6 and (CH)2NH . . . . . 42
Preparation of (CH3)2DNBH3 from (CH )2ND2Cl and
LiBH4 d C *. * *. 46
Hydrolysis of (CH )2DNBD3 in 0.1 M hydrochloric
acid. . . . . . . . 52








Page


Determination of reaction conditions for the
hydrogen elimination reactions. . . . . 53
Hydrogen elimination on.heating dimethylamine
boranes . 55
Experiments to eliminate possibility of isotopic
interchange during the elimination reactions. 58

I. Heating of D2 and H2 in the presence of
mercury vapor . . . . . 58
II. Heating D2 with (CH )2HNBH3 and
(CH )3 NBH3 to determine if exchange
occurred. . . ..... . . 58
III. Heating of (CH )2DNBH3 to determine if
exchange occurred between ND and BH
within the molecule . . . . . 63
IV. Heating of (CHE)2DNBH3 and (CH )2HNBD to
determine if amine exchange occurred. 65

DISCUSSION OF RESULTS . . . . . . . . 68

Possibility of hydrogen-deuterium exchange . . 68
Heating mixtures of dimethylamine boranes
containing various distributions of hydrogen
isotopes for one hour . . . . . 76
Heating mixtures of dimethylamine boranes
containing various distributions of hydrogen
isotopes for twenty-four hours. . . . . 82

CONCLUSION. . . . . . . . . .. . 88

SUMMARY . . . . . . . . .... 90

PART II. SYNTHESIS OF TRIMETHYLAMINE CHLORO-
BORANES

INTRODUCTION. . . . .. . . . .. 92

EXPERIMENTAL. . . . . . . . . . . 95

Nomenclature . . . . . . . . . 95
Reagents and purification. . . . . . . 95
Instruments . . . . . . . . 96
Extraction of BN compounds from the reaction
mixture . . . . . . . . . 97
Infrared spectral analysis . . . . . . 99
Nuclear magnetic resonance spectra . . . . 101







Page


Reaction of (CH3)3NBH3 and HgC12 . .. . . 109
Reaction of (CH3)3NBH3 and HgC12 on a large scale. 110
Reaction of (CH 3) BH2C1 and HgC12 . . ... 114
Attempted reaction of (CH 3)3NBHC12 with HgC12. . 115
Relative rates of reaction of (CH3)3NBH3 with
HgC12 and HC1 in ether at 0. . . . . 116
Reaction of (CH3)3NBH3 and HgC12 in the autoclave. 118
Reaction of (CH3) 3NBH3 and HgC12 in presence of
acetic acid in benzene. . . . . . 119
Reaction of (CH3)3NBH3 and Hg012 in water and in
potassium chloride solutions. . . . . 120
Reaction of (CH )3NBH3 and HgC12in water--the
change in pH with time. . . . . . . 121
Reaction of (CH3)3NBH2C1 and (CH3)3NBHCi2 with
HgC12 in water--the change in pH with time. . 125
Reaction of (CH3)3NBH3 and excess HCl(g) . . 126
Reaction of (CH )3-NBH3 and HCl(g) in benzene . 128
Reaction of (CH-) NBH and concentrated HCl(aq) in
water . . . . . . 129
Reaction of (CH ) cNITBH3 and concentrated HCl(aq) in
benzene . 150
Reaction of (CH3) NBH3 and concentrated HC1(aq) in
carbon tetrachloride. . . .. . . . 131
Reaction of (CH 3)NBH3, (CH ) NBH2Cl and
(CH )3 BHC12 with (CH ) iHCl1. . . . . 131
Reaction of (CH3)3TBH2C1 with SbCl5. . . 135
Reaction of (CH3) NBH3, (CH3)3NBHI2C1,
(CH3)3NBHC12 and (CH3)3NBC13 with SbCl . . 137
Reaction of (CH3)3NBH3 with SOC12. . . . . 138
Reaction of (CH)NBH3 and S02C12 . . . .. 139
Reaction of (CH)3 NBH3 and ZnC12 in glacial acetic
acid. . . . . . . . 140
Reaction of (CH);NBH3 and (iCHO)I NBC1I in an
autoclave and the stability of the mono- and
dichloroborane adducts under these conditions 143












DISCUSSION OF RESULTS AND CONCLUSIONS .

Reactions of (CH3)3NB3H3 and HgC12. .
Reaction of (CH 3)NB3H3 and (CH3)3NHC1.
Reaction of (CH 3)NBHH and SbC15 .
Reaction of (CH3) NBH3 and SbC13 . .
Reaction of (CH3)3NBH3 and S02C12. .
Reaction of (CH 3)NBH3 and SOC12 . .
Conclusions from the reactions . .
Thermal stability of the adducts . .

SUMMARY . . . . .. . .

BIBLIOGRAPHY. . . . . .

BIOGRAPHICAL SKETCH . . . .


* * *

* * *
* * *
* * *
* * *
* * *
* * *
* * *
* * *

* * *

* * *

* * *


vii


Page

146

146
158
161
162
164
165
166
169

173

175

178










LIST OF TABLES


Table Page
1. Analysis of Dimethylamine Boranes . . . 7

2. Pyrolysis of B2D6 . . . . . 8

3. Calculation of Per Cent Deuterium in the
Deuterated Dimethylamine Boranes from Infra-
red Spectra Using the CH Deformation Peak as
the Internal Reference. . . . . 14

4. Sensitivity Coefficient of Mass Spectrometer
for H2, HD and D2 . . . . .. 21

5. Tendency for Parent Ion to Lose a Hydrogen
or Deuterium Atom . . . . * *. 25

6. Reaction of (CH3)3NBD3 and BF3(g) . . . 30

7. Reaction of (CH3)31BH3 and B35(g) . . .. 33

8. Preparations of (CH3)3ND. . . . .. 41

9. Preparation of (CH3)2HNBH3 Containing Various
Distributions of Hydrogen Isotopes. . . 44

10. Results of Heating (CH3)2HNiBH3 Containing
Various Distributions of Hydrogen Isotopes. 45

11. Per Cent BD and NH Bonds in (CH3)2DDNBH3
Prepared from (CH3)21ND2Cl and LiBH4 . . 50

12. Reaction Conditions for H2 Elimination
Reactions . . . . . . . .54

13. Results of Hydrogen Elimination by
Dimethylamine Boranes . . . . . . 56

14. Reaction of (CH3)2HIfBH3 and (CH3)3NBH3 with
D2 . . . . . . . . . . 64


viii










Table Page

15. Infrared Spectra of (CH)3 53BH and the
Trimethylamine Chloroboranes. . . . . 100
16. B Nuclear Magnetic Resonance Spectral
Results . . . . . . . . 106
17. Reactions of (CH3)3NBH3 and HgC12 ... . 111
18. Reaction of (CH3) 3NBH3 and HgC12 in Water and
KC1 Solutions . . . . . . .. 122

19. Reactions of (CH3)3NBH3 and Trimethylamine
Chloroboranes with (CH3)NHC1 . . . . 133
20. Reaction of (CH3)3T BH3 and Trimethylamine
Chloroboranes on Heating. . . . . . 144










LIST OF FIGURES


Figure

1. Infrared spectrum of (CH3)2HNBH3 . .

2. Infrared spectrum of (CH3)2DNBH7 .

3. Infrared spectrum of (CH3)2DNBH3 after
heating . . . . . . . .

4. Infrared spectrum of (CH3)2HNBD3 . . .

5. Infrared spectrum of (CH )2DNBD3 . . .
6. Infrared spectrum of (CH3)2HNBH3 after
heating. . . . . . . . . .

7. Mass spectrometer sensitivity coefficient
H2, HD and D2 as a function of the total
pressure . . . . . . . . .

8. Mass spectrum of (CH3)2HIHBH3 at 70 ev. .

9. Mass spectrum of (CH3)2DN3BH at 70 ev. .

10. Mass spectrum of (CH3)2HNBD3 at 70 ev. .

11. Mass spectrum of (CH3)2DNBD3 at 70 ev. .

12. Infrared spectrum of (CH3)3NBD. . .

13. Infrared spectrum of B2D6. . . .

14. Change in total pressure with time for the
reaction of excess (CH3)3NBH3 and BF3(g) )

15. Change in total pressure with time for the
reaction of (CH )3 BH and excess BF3(g) .

16. Infrared spectrum of (CH3)2DNBH3 prepared
from (CH3)2l-ND2C1 and LiBH4 . . .

17. Infrared spectrum of (CH3)3BH3 after
heating with D2 for one hour . . .


Page

S 9
S 10

. 11

S 12

S 15


20

23

23
24

24

28

31

34

34


49


60








Figure Page
18. Infrared spectrum of (CH)2HNBH3 after
heating with D2 for one hour . . . . 60
19. Infrared spectrum of (CH3)2HNBH3 after
heating with D2 for twenty-four hours. . 61

20. Infrared spectrum of (CH )3NBH3 after
heating with D2 for twenty-four hours. . 62

21. Mass spectrum at 70 ev after heating
(CH3)2DNBH3 and (CH3)2HNBD3 for twenty-four
hours. . . . . ..... . . 66

22. Infrared spectrum of (CH3)3BH2C1. . . 102

23. Infrared spectrum of (CH3)3NBHC12. .... 103
24. Infrared spectrum in 300-600 cm1 region of
(CH3) NBH3 and the trimethylamine chloro-
boranes. ...... .. . . . ... 104
25. B1 Nuclear magnetic resonance spectrum of
(CH3)3NBH2C1 . . . . .. . .... 107
26. B1 Nuclear magnetic resonance spectrum of
(CH3)3NBHC12 .............. 108
27. Change in pH with time during the reaction
of (CH3)3NBH3 and HgC12 in water . ... 124
28. Change in pH with time during the reaction
of (CH3)3NBH2C1 and (CH3)3NBHC12 . .. 127
29. Infrared spectrum of the reaction product of
(CH3)3NBH3 and ZnC12 in glacial acetic acid. 142
30. Comparison of product on heating
(CH3)3NBHC12 with and without (CH3)3N
present. .. . . ... . . .. 145












PART I. MECHANISM OF DEHYDROGENATION OF
DIMETHYLAMINE BORANE


INTRODUCTION


When dimethylamine borane is heated, hydrogen is

eliminated and dimethylaminoborane is formed. The mechanism

of this reaction should be the same as for the first step

in the production of borazenes, for example, N-trimethyl-

borazene, by heating monomethylamine borane. Thus, the

reaction mechanism, or molecularity, would be worthy of

investigation.

The reaction of dimethylamine borane to yield hydro-

gen and dimethylaminoborane does not lend itself readily to

common methods of kinetic determination such as measuring

the increase in total pressure or the concentration of any

single species. This is due, in the first case, to such

reactions as the dimerization of dimethylaminoborane or the

disproportionation of the dimethylaminoborane (7) which

occur at significant rates in the temperature range at which

hydrogen elimination can be conveniently measured. In the

second case, the separation of unreacted dimethylamine

borane, or the separation of dimethylaminoborane from the

reaction mixture, would be difficult because the reaction

would be occurring while the separation was being carried out.








2

Since conventional kinetic studies were impractical

for the most part, the following method was used to yield

data which could be used to determine the reaction

molecularity. N-deuterodimethylamine borane-d3 and di-

methylamine borane in a 1:1 molar ratio were heated and the

non-condensible products analyzed in a mass spectrometer.

The ratio of H2:HD:D2 found was compared to that expected

for either a unimolecular or bimolecular reaction. The

results indicated a bimolecular reaction and a kinetic

isotope effect. The isotope effect was investigated using

various isotopic distributions of hydrogen in the dimethyl-

amine borane and analyzing in the mass spectrometer the

gaseous products eliminated on heating. The established

isotope effect was that hydrogen atoms were eliminated more

readily than deuterium atoms.

The possibility of hydrogen-deuterium exchange re-

actions occurring during the elimination reaction was

investigated thoroughly.











EXPERIMENTAL


Nomenclature

The compounds formed by the reaction of an amine and

diborane wera named as amine adducts of borane. The follow-

ing is the list of amine boranes in Part (I):
dimethylamine borane, (CH3)2HNBH ;

dimethylamine borane-d3, (CH3)2HN3D3 ;

N-deuterodimethylamine borane, (CH )2DNBH ;

N-deuterodimethylamine borane-d3, (CH3)2DNBD3 .

Origin of reagents


D20:

(CH3) 3NH3

(CH3)2NSH:

S02C12:

BF3 :

C4H9Li:

(CH3)2HITBH3:

NaBD 4:

LiBH 4:

Purification


Tracerlab, 99.7% D20
Callery Chemical Co.

Matheson Co., Inc.

Matheson, Coleman and Bell Div.

Matheson Co., Inc.

Foote Mineral Co.
Chemical Procurement Laboratories

Alfa-Inorganics

Metal Hydrides, Inc.

of reagents

used without further purification--being
handled in a N2 atmosphere.










(CH3)3NBH

S02C12

(CHi3)2NH


BF3


C4H9Li


(CH3)2HNBH

(CH) 3NBD

NaBD4

LiBH4


sublimed once, then resublimed into the re-
action flask (or tube).

bp 68-700C, was used without further purifi-
cation--transferred in a N2 atmosphere.

stored over Na for over 24 hours in freezer
compartment of refrigerator, then distilled
into reaction flask (or tube).

distilled from a -780 trap through a -1190
trap into a -1960 trap, then distilled into
reaction tube.

used without further purification--trans-
ferred with a syringe under a flowing stream
of N2.

sublimed once, then resublimed into the re-
action flask (or tube).

sublimed after preparation and then resublimed
into reaction tubes.

used without further purification.

used without further purification.


Instruments

The vacuum system used in the experimental work was

similar to the vacuum line described in Synthetic Inorganic

Chemistry by W. L. Jolly (21). Apiezon N grease was used

on all ground joints in the system.

A Bendix Time-of-Flight mass spectrometer was used

to obtain the mass spectra.

A Beckman IR-lO or a Perkin-Elmer 21 spectrophoto-

meter was used to obtain the infrared spectra in either

the gas phase or in a carbon tetrachloride solution.










General method for the analysis of the dimethylamineboranes

Dimethylamineborane was sublimed from a weighed

storage flask into a 50 ml round bottom flask. After the

sublimation, the storage flask was weighed, the difference

in weight being the amount of sample to be analyzed.

Analysis was based on the equation


(CH )2N-IBH3 + 2H20 + H 130+ (CH )2NH2+ + B(OH)3

+ 3H2


[1]


The compound was first hydrolyzed by condensing 20

ml of 0.1 N HC1 (Acculute) into the flask containing the

dimethylamine borane. Hydrolysis was allowed to continue

overnight at room temperature. The contents of the re-

action flask were condensed in a liquid N2 bath and the

non-condensible gas was transferred into a calibrated bulb

by a Toepler pump. The amount of hydrolyzable hydrogen was

thus obtained.

The acid solution from the hydrolysis of dimethyl-

amine borane was transferred into a 400 ml, boron-free glass

beaker. The boron was determined as boric acid using the

mannitol titration method.

The amount of nitrogen, as dimethylammonium ion,

could be determined since a known amount of strong acid had

been used to hydrolyze the sample. The difference in the

equivalents of strong acid added initially and the equiva-











lents of base necessary to neutralize the strong acid

remaining after the hydrolysis reaction was the amount of

strong acid neutralized by the dimethylamine.

Using this method, the following data in Table 1

were determined.

Pyrolysis of B2D6


Diborane-d6 was pyrolyzed by passing the gas through

a 9 mm Vycor tube, 37.5 cm long, surrounded by a 0.75 inch

stainless steel pipe and heated by two Meeker burners. The

gas was allowed to pass slowly into the tube. Attempts to

make more than one pass of material through the hot tube

did not increase the amount of non-condensible gas; evi-

dently no condensible material passed through the hot tube.

The non-condensible products were Toepler pumped into a
/-
flask and analyzed in the mass spectrometer. Results of

these experiments were as follows, in Table 2.






















OL 0
00 0



00 0
00 0
* *
HH H



00 0



00 0









NH H\
(\0 H '-\
* *


LC\E'- LCUM\


C00M CUC0
JC\j OJC\j

coo3 cOO
r-i,-\ i \ J




rd rd



O CO'd
H H


S0 0
o do



M4 OC




0 0


O


O
0




0
0

r-t






0
**
O'-.O'


LSN' N-\ r-N
0 r- u\
ir UM S


00 0 Lr\ 0000
00 N-\CO cc O
oj r(\j o rC^


Lr\0 0 t rc\
z-" 000 KlOJ
-- Oco t%" CMO
-t r-. r- OJ Od


rd rc rd
C .) 4O
d d d



do do do
cdl crl c0

S-i 04-i
0 0 0 d 0









v v v


CO






0








H


O

H
-i:
1 Cl <


(a)



Cd
) 4-I
r-t
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o c

0 0
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Td









TABLE 2

PYROLYSIS OF B2D6


Prepared by B2D6 Per Cent Per Cent
mmoles Reaction D2 HD H2
mmoles 2 2

(CH3) 3NBD3 +

BF3(g) 0.098 105.8 81.5 18.5 -

NaBD4 + BF (g) 0.12 88.9 91.0 8.4 0.5


Infrared spectral analysis

The spectra of the dimethylamine boranes (Figures 1,

2, 3, 4, 5) were taken on a Beckman IR-10 spectrophotometer,

using matched cells 0.2mm thick and the slow scan speed.

The compounds were dissolved in Fischer spectroanalyzed

grade carbon tetrachloride and the same solvent was used as

a blank in the reference beam. The absorbency, A, expressed
Intensity blank
as the log ntnityion was calculated from the
Intensity solution
infrared spectra in which transmittancy was plotted as a

function of the wave number.

The absorbency of the CH deformation peak at 1475 cm-1

was used as the internal reference and all calculations were

made with respect to this peak. The results are given in

Table 3.




















Clj



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0








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cCj
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H c












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o~~ 0
'.0 4
G~Ue~w~ue~~4.UG .C&










































































aouBiTulssuea Juao Jad























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r-



rl


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12








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0D KI 0
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o 00




















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M A
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00
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The ratio of the absorptivities of the BH:CH and the

NH:CH in the spectrum of the completely undeuterated sample

were found to be 1.90 and 0.992, respectively. The per cent

NH and ND were calculated as follows:

ANH aNH CNH
CH aCH CH

ANH/ACH calculated from spectra

aNH/aCH absorptivity ratio from spectrum of undeutera-

ted compound

CNH/CCH ratio of concentrations

Assume in partially deuterated compounds that

CNH + CND = CCH

CBH + CBD = CCH

This assumption allowed C D to be determined without the

actual absorbency being known. This was necessary since

the ND and BH stretching frequencies both occur between

2300-2500 cm-l It was not possible to separate the ab-

sorbency due to each vibration. Since (CH3)2DNBD3 was known
not to be completely deuterated from mass spectral data of

the B2D6 pyrolysis product, the absorptivity ratio of BD:CH

could not be obtained for its infrared spectrum. Therefore,

the ratio of the absorptivities for BD:CH was assumed to be

the same as that for BH:CH.









The absorptivity ratio of BH:CH for the volatile re-

action product after heating (CH3)2HNBH3 for thirty-four

hours at 1000 was 1.50 (Figure 6). Thus, one of the BH

containing products which was formed when dimethylamine

borane was heated, did not absorb as strongly in the BH

stretching vibration region as did the original starting

material. This could cause a lower estimation of the amount

of BH-containing material after heating than would actually

be present and therefore introduce an error in any calcula-

tions made using the BH stretching absorption.

The absorption in the 1700-1800 cm1 region which

was attributed to the BD stretching vibration in the mole-

cule (CH )2HNBX3 [X=H and/or D] did not occur at exactly

the same wave number in each spectra. The absorption varied
-1
from 1755 to 1785 cm Qualitatively, this variation

appeared to be concentration dependent. The greater the

concentration of BD bonds in the molecule the larger the

wave number at which the absorption occurred. The absorption

for the BD stretching vibration in (CH3)2DNBD3 occurred at

1785 cm-1 and for (CH3)2DNBE3 containing 5 per cent BD bonds,
at 1735 cm" An explanation for this variation could be

that a shift in the stretching vibration occurred in the

-BH3 group as the hydrogen atoms in the -BH3 group were re-

placed by deuterium atoms. The largest shift was implied by

the spectra at low D2 percentages when mostly BH2D groups

should have been present.
























0 o
O











--o
0









0
> >











C)






0


O







0
o












0













o. 0
0










0C






















0- 00 0 0
r

^=

*r ---
^*^,

-- -- -------- = ~ --- .
., __________ ---*-- >.
/-- -***

.1^ ,, :
_^-t --- g ------------ ---- ^ ----- ^ ------ ^ ----- j ------ ---






0 0 0 0
00 ^0-^- (
souB~usuej. q~uo js









Mass soectral analysis

A Bendix Time-of-Flight Mass Spectrometer was used for

the analysis. The sensitivity coefficient of the spectro-

meter to H2 and D2 was determined before each set of analyses,

using commercial samples of hydrogen and deuterium gas. The

sensitivity coefficients used in calculating the data were

obtained at the same total pressure as that in the sample.

In calculating the results of the hydrogen elimination re-

action the sensitivity coefficient for HD was assumed to be

intermediate between that of H2 and D2. This assumption

proved to be a valid one as may be seen by the graphs of

pressure versus sensitivity coefficient in Figure 7.

Three sets of sensitivity coefficients were determined

and listed in Table 4. A sensitivity coefficient for HD

was determined from a gas sample prepared by the hydrolysis

of CaH2 with D20. This gas sample contained small amounts

of D2 and H2, but it was predominantly HD. The spectra

were corrected for the presence of D2 and H2 and then the

sensitivity coefficient of HD was calculated. The variation

in the sensitivity coefficients with total pressure was

determined and plotted in Figure 7. In samples containing

D2, the H2 content was determined from the peak at m/e 2

after subtracting the portion due to D+. The necessary

data were obtained from the intensity ratio of m/e 4 and

m/e 2 peaks in the mass spectrum of pure D2.













O





0O
O O


1.60 -




1.40




1.20 -


0


0


o
^^~~~o


I 6
60


1 I
140


I 1
180


220


Pressure, microns
Fig. 7.--Mass spectrometer sensitivity coefficient of H2,
HD and D2 as a function of total pressure.
(0) D2; (G) HD; (o) H2.


2.20 -




2.00-




1.80-


1.00




.80


- -


















0
Cm Cto 0


oJ a 0 o *


/ -pq -r* 0 4+
N^ HQ o a *
SC OH Od 0 .
c 00 r-X l 4- '0 0
Sr 0 0 >-NP 0

d 0 a -4 0-p
coj o + o j o 0
o rl E 0- a o -l
SO .l a- b
o 't 0 d d ( o- I
O 0 4- CO 0 *r*

E1 P 0 I
SO -H O
0 P A C ca O

0 0W


E- C 1 0
EO 0
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o H m 1-e-
dH rd ( C
0 r, 0)




E- 1 4- rd ,C r
CdLCo 0 %
H C!S 0 0) 0P
0 r P *HH 0 a Y




W P: P 0
o o "- o oo
O C;H L N H rd

H 0 rH 0C
E-1 0 0 *H rP

H 0 0 0C
E- P 4-> F-'d H
H *i *j-4 00) 0a
M > g-P 0
S 4 OJ CM
m o1
0 0
CO 0 0 d









The mass spectra of the solid dimethylamineboranes

were obtained at 70 ev by placing the sample on the end of

a probe which extended into the ionization chamber. The

probe was at room temperature during the measurement of the

spectra. The vapor pressure of dimethylamineborane at room

temperature was sufficient to produce good spectra. For

the results of these analyses see Figures 8, 9, 10 and 11.

The mass spectra of the solid compounds showed a low

intensity peak at the m/e corresponding to the mass of the

parent compound. The mass peak of m/e one less than the

parent peak, and the parent peak had a ratio of 8.4 in the

cases where the hydrogen was bonded to the boron atom and

a deuterium bonded to the nitrogen atom compared to 7.9 for

the reverse case where hydrogen was bonded to nitrogen and

deuterium to boron. This suggested that the BH bonds were

lost more readily than NH bonds. The spectra of the com-

pletely deuterated and undeuterated compounds also showed

the same trend as indicated in Table 5. The ratio of the

m/e peak of mass two less than the parent peak, to the parent

peak, implied that a BD bond was lost much more readily than

an ND bond.

The most intense m/e peak in each spectrum corres-

ponded to the loss of a deuterium atom when the compound

contained BD bonds and to the loss of a hydrogen atom when

the compound contained BH bonds. But the numerous peaks, in












S\0


--1


Lo





- rD


-o a,
\o
10












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3


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1




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ho







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0
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r



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OO
a













-0 0
0 l








I
-0 r-"

*
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0 D
aH 5H
0 -




S m N 0 0r3

C) *\ 000*
0 0 tC Cx L LCa'


S 0 0 0 0
B m*
o p H*)* ** * LA




H CH 0 C\ r-i C
o d
4 i 0HKH CO 0-

0 02-P LA


>0 H 0 00
a 0 0 0 0




O
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0
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u u o o o
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each group of peaks differing only by one m/e unit, suggested

that the CH bonds in the methyl groups were also being broken

under the conditions at which the spectra were obtained.

This would make any quantitative use of the relative peak

intensities open to doubt as to whether the hydrogen atom

lost had been originally bonded to a carbon, nitrogen or

boron atom.

Preparation of (CH )3IBD3 from (CH ) NBH3 in an acidic D20

solution (11)

Sulfuryl chloride (0.5 ml) was pipetted into a flask

containing deuterium oxide (20 ml) in a dry nitrogen atmos-

phere and stirred magnetically for twenty minutes. Tri-

methylamineborane (15.7 mmoles) was dissolved into 50 ml of

anhydrous diethyl ether in a 200 ml round bottom flask. The

deuterium oxide solution was poured into the ether solution

and immediately the flask was fitted with an adapter for the

vacuum system, attached to the system, and submerged in

liquid N2, and evacuated.

The reaction flask was warmed to room temperature

(240) and stirred magnetically. After six hours, the re-

action mixture was condensed in liquid N2 and, in approxi-

mately a 400 ml volume, there was 95.5 mm of non-condensible

gas. The D20-ether mixture was transferred to a separatory

funnel and the reaction flask washed with a 20 ml portion of

ether which was then added to the reaction mixture. The









layers were separated, keeping the ether layer in the

separatory funnel. Excess anhydrous potassium carbonate was

added to the ether solution and the mixture was set aside

for forty-five minutes. The ether solution was transferred

into a 200 ml round bottom flask, washing the K2003 with two

20 ml portions of anhydrous ether and the wash solutions

added to the ether solution.

The ether was removed by distilling under vacuum from

room temperature into a liquid N2 trap. When liquid ether

was no longer visible, a -780 bath was placed about the

flask and the last of the ether removed into the liquid N2

trap. This was to prevent loss of product by sublimation.

A white solid residue remained. A white product was sub-

limed from this residue to give a 74.2 per cent yield.

The infrared spectrum (Figure 12) of the sublimed

product in CC14 solution agreed with the spectrum of tri-

methylamineborane with the peaks attributed to a BD stretch-

ing vibration shifted to longer wavelengths. There was a

peak in the region of the BH stretching vibration, but it

was less intense than the BD peak. Assuming the absorptivity

coefficient, a, to be the same for both the BD and BH con-

taining compounds, from Beer's law, A = abc, the concentra-

tion of the BH compound was calculated to be 2.7 per cent of

the concentration of the BD compound. No other analyses

were made of this compound.











80






70










o

250







-pI
C,




30 -






20






10 -



2500 2200 2000 1800

Wave number, cm-1
Fig. 12.--Infrared spectrum of (CH3)3NBD3.










Preparation of B2D6 from (CH )3NBD5 and BF (g)

Trimethylamine borane-d3 (4.0 mmoles) was sublimed

into a reaction tube fitted with a stopcock and a side arm

filled with mercury such that if the tube were inverted the

mercury sealed the stopcock from the contents of the tube.

Boron trifluoride gas was entered into the vacuum system

from the storage tank. The gas was purified by distilling

from a CC14-CHC13-CO2(s) trap (-780), through an ethylbromide

slush (-1190), into a liquid N2 bath (-1960), before con-

densing into the reaction tube. The reaction tube was then

warmed to room temperature and set aside for an extended

period of time.

A liquid phase was present in the reaction tube after

the tube warmed to room temperature, but the liquid phase

slowly disappeared.a After eighty to ninety hours at room

temperature, the reaction tube was attached to the vacuum

system, the products condensed in liquid N2)and any non-

condensible gas removed. The reaction tube was then warmed
to -780 and the volatile fraction was removed and condensed

onto excess anhydrous diethylether. Any unreacted BF3(g)
would form the etherate and the B2D6 could be separated from

it. The ether flask was warmed to -780 and a product, B2D6,


aUsually this occurred overnight. Care must be taken
to prevent this liquid phase from holding the mercury next
to the stopcock on solidifying and thus sealing all gaseous
product in the tube.









was distilled from a -780 bath, through a -119 bath, into
a -1960 bath. The distillation was done rapidly to prevent

contamination of the B2D6 with ether vapor. The material
in the -1960 trap was diborane-d6.
The results of the experiments were as follows in
Table 6.
TABLE 6
REACTION OF (CH3)3NBD3 AN D BF3(g)


Compound Mmoles Yield Yield Vapor Pres-
mmoles Per Cent sure at CS2
Slusha
(CH)3NBD3 4.00 1.64 82.0 239.0 mm

BF3(g) 5.71
(CH)3NBD3 2.11 0.90 84.9 238.5 mm

BF3(g) 3.78

aLiterature value is 238.3 mm (6).

The infrared spectrum of the B2D6 was in agreement
with the reported spectrum (43). The resolution of the
spectrum (Figure 13) was poor but it did show a low intensity
at 2500 cm-1 which was due to a BH stretching vibration, and
the intense BD stretching vibrations at 1810-1840 cm1 and

1954 cm-1. A rough estimate of the concentration of BH to
BD from Beer's law gave a ratio for CBH/CBD of 0.15. The
absorptivity of BH and BD were assumed to be equal in this
calculation.






























C)




0 ,

00-






30-





20-







2500 2200 2000 1800

Wave number, cm-1


Fig. 13.--Infrared spectrum of B2D6.









A sample of the diborane-d6 was pyrolyzed and a mass

spectrum run on the products. For the results of this

experiment see Table 2.

Variation in the per cent reaction of (CH,) NBH, and BF (g)

to yield B2H6


Boron trifluoride will displace diborane from tri-

methylamine borane according to the equation (28):

1
(CH 3)NBH3 + BF(g () -(CH ) BF3 + B2H [2]

The extent of this reaction in mercury-sealed bulbs

was studied as a function of time in order to determine the

optimum time for the practical synthesis of diborane at

room temperature. The following variations, listed in Table

7, in the per cent reaction were determined.

The extent of reaction was followed by measuring the

total pressure in the reaction flask as a function of time.

For complete reaction, the total pressure should be one

half of the initial pressure according to equation [2]. The

graphs (Figures 14 and 15) showing the variation in total

pressure with time indicated that after fifty hours the re-

action, for practical purposes, was complete since the addi-

tional amount of diborane produced in the next thirty hours

did not warrant the extra time spent. The plots indicated

little difference in the rate of decrease in total pressure























LPl


^- N Cd- d- N N K1 C C


LR rWc L>\ Nt< r(\






L\ CNJ tO 0 -

CD -d- t 00- 0
V. Dz DC'cO


LD OJ Lr\





D 0o

C- co co


),\ c"- c"- co WN ti Z- 0
t"- ;- tD cO oO .D 0 .O O
OIO
00000 C~lrHO0


( JL OJ O -










(L' Lt\ L-> L0
N 0 0 0
\ C\J C\j nC\j


C'-~





0


O4

0
H
E-


)
0 ) MS
AP40) N
- P-


CO









p
0)





0r

F-e
-p




H
0










0)0
rC








10-N
co









rd
m *






00

0 C
CO








-P a
c0



0)
'
*r


a
H 0





0) d








oi
! C
aw




I P


CO
0)

H


0 \ i CO
,, to 0- 0-
*\ %'- %

qc







O 0
r^ C 0 i-
-s *

r^ O --O


H -)
WD 0



+


rcd




00
o o
O v















































0 0
\O CN
C^\ C\


nuau 'ajnssaja


o -P
.1-4 ca


O m


0) C


00 M
o C oh
-o ~ -i-' 0

r 0 0)


(1) Ot)
-- *C 0


-4 OX




*
U. C 0








0 4
CQ


*,


















3 cl


.0 0

-P




,) an



E- 0 C
S-H
H 00





C c $-





M




r-q b.0
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rx 0 ^
1 -P

?-
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0 0
C0 c\


CO
co










with time whether BF3(g) or (CH3)3NBH3 were in excess, al-

though the sample containing excess BF3(g) had a 10 per

cent greater extent of reaction.

The data implied that at room temperature the re-
action was only 85 per cent complete in eighty to ninety
hours. It could be possible for the reaction mixture to

reach an equilibrium state in which B2H6 was displacing

BF3(g) in the reverse reaction according to the equation:
1
(CH3) NBH + BF3(g) = (CH ) NBF + 2 B2H [3]

An equilibrium such as this could explain the small change
in total pressure after sixty hours. The attainment of an
equilibrium state is supported by the work of Miller and
Onyszchuk (28)2who found in forty-five minutes at 1300-1400.

an average displacement of 23.4 per cent BF3(g) in

(CH3)3NBF3 by B2H6 and an average displacement of 83.3 per
cent B2H6 from (CH3) 3NBH3 by BF3(g). However, Graham and
Stone (17) reported that after heating B2H6 and (CH )3NBF3
for twelve hours at 800 the gas did not show any evidence
of BF3 in the infrared spectrum. They concluded that no
reaction had occurred under these conditions. The implica-
tions appear to be that for the equilibrium to be established,
the temperature must be greater than 800 or the time must be

longer than twelve hours. But the data show that the rate
of displacement depends greatly on temperature. Miller and










Onyszchuk (27) achieved the same per cent displacement in

forty-five minutes at 1300-141O that we obtained in approxi-

mately ninety hours at room temperature (230-250).

The displacement reaction proved to be an impractical

method for preparing diborane. It was used in this work to

prepare deuterated diborane. R. E. Davis (11) had reported

the exchange of boron hydrogens in trimethylamine borane

with acidic D20 to be rapid and quantitative. In this

manner, (CH )3NBD3 could be prepared and then B2D6 displaced

from the adduct by BF3(g). Thus, B2D6 could be prepared

from readily available and inexpensive starting materials

without the use of deuterium gas to deuterate the diborane,

or without the use of a borodeuteride salt.

The displacement reaction did not give diborane of

sufficiently high deuterium content and B2D6 was prepared

afterwards with HTaBD4 as the source of deuterium.

Preparation of B2D6 from NaBD4 and BF3(g) in diglyme (4)

Sodium borodeuteride (1.0 gram) was placed in a 100

ml round bottom reaction flask in the Dri-Lab controlled

atmosphere box.a A stopcock adapter for attaching the flask

to the vacuum system was added to the reaction flask. The

flask was then attached to the vacuum system and was evacua-

ted.

aA static charge on the powdered NTaBD4 prevented a
quantitative transfer of the material from the glassine
weighing paper into the flask.










The diglyme (ethylene glycol dimethyl ether) to be

used as the solvent was refluxed and distilled from sodium

metal, again distilled from LiAlH4, and finally transferred

from LiAlH under vacuum into the reaction flask at -1960C.

Boron trifluoride was condensed into the vacuum

system directly from the storage tank. The BF3 was then

purified by distilling it from a CC14-CHC13-C02 trap (-780)

through an ethyl bromide slush trap (-ll19) into a liquid N2

trap (-1960). The gas was then condensed into the reaction

flask submerged in a liquid N2 bath. A total of 53.14

mmoles of BF3 was condensed into the reaction flask. The

molar ratio of BF (g) : NaBD~ was 2.2:1.

The reaction flask was allowed to warm to room tempera-

ture (220). After thirty minutes, the reaction was cooled

to -780 and the volatile fraction removed into a -1960 trap.

This procedure was repeated twice with reaction times at

220 of thirty minutes and sixty minutes. The total amount

of volatile material removed from the reaction flask was

10.76 mmoles. The material had a vapor pressure of 254.0 mm

at carbon disulfide slush temperature (-111.90). The

literature value (6) for the vapor pressure of B2D6 at this

temperature was 238.5 mm.

To remove any possible BPF impurity in the B2D6, the

gas was condensed onto anhydrous diethyl ether. The gas-

diethyl ether mixture was warmed to -780 and the volatile










portion was transferred into a liquid N2 trap. After thirty

minutes, 10.55 mmoles of volatile material had transferred

from the ether flask. This material had a vapor pressure

of 258.5 mm in a carbon disulfide slush bath, in agreement

with the previously cited literature value.

An infrared spectrum was run on the material before

it was reacted with ether. The spectrum was in agreement

with that reported for B2D6 (45). No spectral evidence was

noted for the impurity which was removed by the diethyl

ether. There was a low intensity peak at 2510 cm-. A

rough estimate using Beer's law showed, that according to
this BH peak, the ratio of CBH : CBD was 0.058 assuming that

the absorptivity for BH and BD are equal. The assumption

was correct for the absorptions in the infrared spectra of

(CH ) NBH5 and (CH3) 3NBD3.
A sample of this B2D6 was pyrolyzed and a mass

spectrum run on the non-condensible products. For the

results of this experiment see Table 2.

Preparation of B2H6 from NaBH4 and BF3(g) in diglyme

This preparation was done in the same manner as the
preparation of B2D6 from NaBDL and BF (g) in diglyme. The
amounts of reagents used were 0.4 g (10.58 mmoles) NaBH4 and

22.25 mmoles BF3(g). The molar ratio of BF3(g) : NaBH,

was 2.1:1.










A product was isolated in 78.7 per cent yield (7.05

mmoles) which had a vapor pressure of 225 mm at carbon di-

sulfide slush temperature. The reported value (6) at this

temperature is 225 mm. An infrared spectrum of this compound

was identical with that reported for B2H6 in the literature

(43).

General procedure for preparation of (CH3)2ND

A solution of n-butyl lithium in n-hexane (1.6 M)

was syringed into a 100 ml round bottom flask under a stream

of nitrogen. An adapter to the vacuum system was inserted

immediately into the flask, the contents were condensed in

a liquid N2 bath, and the flask evacuated. Excess dimethyl-

amine which had been stored over sodium metal was condensed

into the flask containing the hexane solution.

The reaction flask was then warmed to room tempera-

ture and immediately a white precipitate appeared. After

thirty minutes at room temperature, the reaction flask was

cooled to 0 for thirty minutes, and then a volatile fraction

was removed into a liquid N2 trap. The transfer was done

slowly to prevent excessive spattering of the white solid

as the liquid phase was removed. The remaining excess di-

methylamine, n-butane, and n-hexane were removed with the

flask at room temperature. A white solid residue, LiN(CH )2,

remained in the flask, according to the equation:










(CH3)2NH + n-qH9Li LiN(CH3)2 + n-C4H10 [43

A vial equipped with a capillary break-off tip con-

taining deuterium oxide (1 ml) was attached to the vacuum

system, the tip of the vial was broken and the D20 con-

densed onto the amide salt in a liquid N2 bath. The re-

action flask was slowly warmed to room temperature and an

immediate increase in pressure was noted. The white solid

had turned dark brown after fifteen minutes at room

temperature. Part of the flask was cooled to 0 and kept

at this temperature for one hour and forty-five minutes.

All the volatile material in the reaction flask was trans-

ferred into a flask containing excess anhydrous potassium

carbonate in a liquid N2 bath. The K2CO3 flask was warmed

to 00 in an ice bath and kept at this temperature for two

hours. The K2C03 mixture was then cooled to -780 and a

volatile fraction removed into a liquid N2 trap, requiring

approximately forty-five minutes. This material was

deuterated dimethylamine. A possible impurity in this ma-

terial would be monodeuterated n-butane due to incomplete

reaction of the n-butyl lithium and the dimethylamine

according to equation [4].

The results of the experiments are as shown in


Table 8.
























So
o
0O
0 42
Cd -i cd
hp-i
>>(




kdr
0 0oH




0 ,

rd



o4
0 Q
0 0
om





N 0










-p


M

0

U,
0
H



E-


Ll\ Lu\





C- --t -




CO r-
* *






















c~ o
* (*
00 0








oj u\ ><
Oj Oj O






H H 8


M
C\j


0
0rd

0 0o
o
*H 0 -p

0 0

o Cd
0o o

o N
0: 0
0 e-




co p





\ o rI



*- 0 0




X p
0 4H- 0
-P 00


c 0 0)

H O *0H
O C I O
0 0

-p-
*H CH *H0
0 (0 -0



d 1 0.



i E-iC )
dHriCt









Gas phase infrared spectra of these different prepa-

rations were identical. The spectra were similar to the

spectrum of undeuterated dimethylamine (34) except for some

shifting of peaks in the 1300 cm-1 to 1000 cm-1 region.

The deuterated amine which had a vapor pressure at 00 great-
11
er than 760mm did have an extra peak at 2150 cm-1. An

attempt to purify this sample by distilling a fraction from

an ethylbromide slush (-1190) into a liquid N2 trap resulted

in an increase in intensity in the infrared spectrum of the

peak at 2150 cm1 in the fraction which transferred into

the liquid N2 trap. The infrared absorption peaks of n-

butane (20) were not detectable in the spectrum. The peak

at 2150 cm-1 could be attributed to a C-D stretching fre-

quency in monodeuterated n-butane. The C-D stretching

frequency in the deuterated methanes varies from 2085 cm1

in CD4 to 2205 cm1 in DCH3 (29). This material was more

volatile than-the amine, which was consistent with the

relative vapor pressures of dimethylamine and n-butane. n-

Butane has a higher vapor pressure than dimethylamine (8).

General method for the preparation of (CH )2HNBH3 from B2H6
and (CH3)2NH

Diborane and an excess of dimethylamine were condensed

into a 50 ml round bottom flask in a liquid nitrogen bath.

A CC14-CHC1 -CO2(s) bath (-780) was then placed about the










flask and it remained at this temperature for an extended

period of time (for the exact reaction times see Table 9).

The excess amine was removed from the flask at 0 into a

liquid N2 trap, and the liquid product remaining in the

flask slowly solidified on storage at room temperature.

Mass spectra of the boranes showed a mass peak of

low intensity corresponding to the mass to charge ratio of

the parent ion, and a high intensity peak at a mass to

charge ratio corresponding to the loss of a hydrogen or

deuterium atom.

The results of the preparations of the variously

deuterated dimethylamineboranes are given in Table 9. For

the method of analysis see page 5. The infrared spectra

are given in Figures 2, 4 and 5.

Each of the variably deuterated dimethylamine

boranes was heated at 100-1020 and the non-condensible re-

action product analyzed in the mass spectrometer for the

percentages of D2, HD, and H2. The results of these elimi-

nation reactions are given in Table 10.

The infrared spectrum of the compounds in carbon

tetrachloride solution, in each case, contained peaks where

the NH, ND, BH, and BD stretching vibrations occur. Beer's

law was used to calculate the relative percentages of each

compound using the CH deformation absorption as the internal

reference. For the results see Table 3.




















pt4 Lr N
0 ON ON ON
o r-O r rd
0 -o rll r*- rlcl rcr
G-o H Hi r-1 rH
1-H *


H
P4
E- erd rd rd rd



o 0o op a aU a C.


p H. -P
0 O O O k PO .N ,-
0 D0 Hrd 0 0 H
o D O a Ot O O O 0 L 0
ZO 4j + 0 *
aN H E I C
0 d o 0
Pq E- C/ -i 0 -4
CZH C -. v *P

E N. 'r ) 0 0 0

C 10 co- 0F-
0 0 4a 0 w



c Erl co C I O G

+m ,M
0cU) 0- W H


H Ur 4 M O0 ri 0 N 0 KH aC A,
% gl O 0O o a U)r .
od
S4-' o- o
lr cd rd
K om oI pi O

Poo COM L)
00 t., 0 C 0 n C
.- 0 OJ O C\ O\ %9 0 N 0






























CO
0



Sco
OR


HO
SH
EH
0 0



M





O H
0
m
F










0
0H
CO


-) *H0
0-
Co

a P












0
a
E-l













rd
0
l-







0






o
0


e- C-
I I *
H- d-


Hl LC\
* *



D 0^
r01 1

cO *
0 0











(2 (0


o o

o4


0 *


C-O uL

o0 0
C -Z


0
*


d-
o

ox


Lr\ C-I 0 0











Inn a P
O t H C'-











CM CM\ CM CM

0 0 0 0
oC or o)
KIN


- I'llJ










Preparation of (CH3)2DNBH3 from (CH3)2ND2C1 and LiBH4

N-Deuterodimethylammonium chloride was prepared by

condensing N-deuterodimethyl amine (7.67 mmoles) into a

tared 50 ml round bottom flask containing deuterium oxide

(1 ml) and thionyl chloride (15 mmoles).a The reaction

flask was warmed to 00. After one and one-half hours, all

volatile material was removed from the flask. The increase

in weight of the reaction flask implied that only 0.86

mmoles of product was formed. The volatile material was

transferred back to the reaction flask.

A gas phase infrared spectrum of the most volatile

materials in the reaction flask was identical to that of

S02(g) (3 ) and mono-deuterated n-butane which was known
to be a contaminant in the (CH3)2ND used. The n-butane
and some of the S02(g) was transferred from the flask at
-780 into a -1960 trap in thirty minutes.

More deuterium oxide (1 ml, making a total of 2 ml)
was distilled into the reaction flask and dimethylamine

(6.3 mmoles) was condensed into the flask. After forty-five
minutes at 00 and thirty minutes at 250, all the volatile
material was removed; the weight gain by the reaction flask
implied 6.48 mmoles dimethylammonium chloride had formed.


aThe hydrogen chloride impurity in the thionyl
chloride was removed by warming the thionyl chloride to -780
and exposing it to a -1960 trap for twenty-five minutes.










The ion should have been almost completely deuterated since

(CH3)2NH2+ is known (38) to exchange rapidly with the solvent

in acidic solution and a large excess of heavy water had

been used. The infrared spectrum in a Nujol mull contained

absorptions in the 1900-2400 cm- region and none greater

than 3000 cm-1, indicating the absence of NH absorption.

The completely deuterated ammonium ion has absorptions at

2214- and 2546 cm1 (30). Therefore, the product should be

primarily the deuterium-containing material.

In the Dri-Lab controlled atmosphere box, lithium

borohydride (approximately 11.5 mmoles) was added to the

flask containing the (CH3)2ND2C1. The flask was attached to

a vacuum system and approximately 25 ml of diethylether

(stored over CaH2) was distilled into the flask. After

forty-five minutes at 0 and fifteen minutes at room tempera-

ture, no evidence for reaction was noted. The reaction

flask was returned to the Dri-Lab and LiBH4 from another

bottle added to the solution. Immediate gas evolution was

noticed. Excess LiBH4 was added and the solution was

magnetically stirred. After one hour when no more gas

evolution was noticed, the reaction mixture was filtered

and the residue washed with approximately 10 ml of ether.

After the ether was removed by vacuum distillation, a liquid

phase containing a white solid remained in the flask.










A small amount of the liquid product was vacuum dis-

tilled from the reaction flask at room temperature into a

-1960 trap. An infrared spectrum of this material showed

absorptions at 3210 cm-1 (NH), 2300-2400 cm-1 (ND,BH), and

at 1750 cm-1 (BD). Since the material distilled so slowly,

it was recrystallized from cold carbon tetrachloride and n-

hexane. The recrystallized product was a solid at room

temperature. It was placed in a vacuum sublimation apparatus,

and the most volatile fraction was removed by pumping on the

sublimator at room temperature and collecting a product in

a -1960 trap. After twenty-five minutes, the cold finger

in the sublimator was cooled to -780 with CO2(s) and the

material was collected for nine hours. The initial material

removed from the sublimator into the -196 trap was a liquid

at room temperature and the compound collected on the cold

finger was a solid at room temperature. The infrared spectra

(Figure 16) of the recrystallized compound and on the

fractions obtained by sublimation were identical and showed

absorptions in the same regions as the material initially

transferred from the reaction flask. The percentages of NH

and BD bond in the compound were calculated from the infrared

spectra using Beer's law. The percentages were calculated

relative to the CH deformation at 1475 cm-1 as the internal

reference. The results were given in Table 11.











49









7 ol








Cdl
o


N
cn





u


0
0
Cd







0



ra
E n




C N
Cd C
cz
0












C0 0
C)
0 S






C-C
cna
C CCC
oZ
4-4~
Na





0 c
0
0 b




0 0 0 0 0
NE


u;ue3~Tsue; ;ua~o aa










TABLE 11

PER CENT BD AND I1N BONDS IN (CH3)2DNBH3 PREPARED
FROM (CH3)2ND2C1 AND LiBH4


Compound: (CH3)2DNBH3 Per Cent Per Cent
BD Nh BD NH

Fraction Absorbency
Sublimed from 0.342 0.201 18.0 20.2
Reaction Flask

Recrystallized
CC14-n-hexane 0.0492 0.0492 14.7 28.0

Recrystallized
First Fraction
from Sublima-
tion 0.0453 0.0414 13.3 23.3

Recrystallized
and Collected
on Cold Finger 0.155 0.167 13.2 27.2










Any dimethylaminoborane impurity should be contained

in the initial fraction sublimed from the reaction flaska

A small impurity of this compound in the spectrum would

cause a low percentage of NE relative to CH in the calcula-

tion, and the absorption at 1750 cm-1 in the spectrum of

dimethylaminoborane would cause a high percentage of BD

relative to CH to be calculated. Another source of error

would be in using the absorptivity ratio of BH:CH in

(CH )2HNBH3 to calculate the per cent BD, the assumption

made here has been shown previously to be a questionable

one. The first fraction sublimed from the recrystallized

compound could also contain an aminoborane impurity. The

percentage of BD and hTH containing compounds show that some

fractionation was accomplished by the method of purification,

but still the recrystallized material before and after

sublimation were essentially the same.

The larger percentage of NH bonds compared to BD

bonds would indicate that hydrogen-deuterium exchange

occurred before the formation of the aminoborane. Thus,

this method of preparation, under the experimental condi-

tions used, did not give a pure product containing deuterium


aDimethylaminoborane has a vapor pressure of 10mm at
230 (39).
See page 17.









only on the nitrogen atom, due to the exchange between ND

and BD bonds prior to the reaction to form the amine

borane.

Hydrolysis of (CH3)2DNBD3 in 0.1 M hydrochloric acid

N-Deuterodimethylamine borane-d3 (0.914 mmoles) was

sublimed into a 50 ml round bottom reaction flask and hydro-

chloric acid (20 ml of 0.1 M) was distilled into the flask.

After nine hours at room temperature, the reaction product

was condensed and the non-condensible gas removed with a

Toepler pump. The amount of non-condensible gas (2.70.

mmoles) corresponded to complete reaction according to the

equation:

(CH )2DNBD + H30 + 2H20 (CH)2NDH+ + B(OH)3

+ 3HD [53

The mass spectrum of the non-condensible gas gave 14 per

cent HD and 86 per cent H2. The 14 per cent HD in the non-

condensible hydrolysis product indicated that the rate of

exchange of BD with the solvent was not so much more rapid

than the rate of solvolysis that all of the deuterium bonded
to boron exchanged before the solvolysis reaction was com-

plete.

R. E. Davis (11) reported only H2 gas produced in the

acid hydrolysis of (CH)3 NBD3 due to the rapid acid catalyzed

exchange of the BD with the solvent. However, the rate of









acid hydrolysis of (CH )2HNBH3 is greater than that of

(CH3) NBH3 (24). Therefore, the BD in (CH 3)NBD3 would

have had more time to exchange before solvolysis than in

(CH )2HNBD .

H. C. Kelly (23) reported that for p-toluidine borane-

d in a 50/50 mixture of dioxane and water with no acid

present, the rate of exchange of BD with solvent was negli-

gible relative to the rate of solvolysis; but that at high

acid concentrations the rate of exchange increased. Kelly

found no primary hydrogen isotope effects in the solvolysis

reaction.

Determination of reaction conditions for the hydrogen
elimination reactions

Dimethylamine borane was heated in sealed glass tubes

for various periods of time and the amount of hydrogen

eliminated measured by transferring the hydrogen into a

calibrated bulb with a Toepler pump. The temperature of

1000 was used for the reactions because it gave a reasonable

rate of hydrogen evolution. In general, the extent of re-

action at low percentages was not very reproducible, since

the small amounts of hydrogen being measured (usually 0.4

mmoles ot 0.03 mmoles in a volume of 105.8 ml) were subject

to experimental error.

The results of the experiments were given in Table

12. These experiments led to the selection of reaction











TABLE 12


REACTION CONDITIONS FOR


H2 ELIMINATION REACTIONS


(CH )pHNBH Time Temperatures Per Cent
mmoles (hour) Reaction


1.54 1 1000 13.5
1.47 1 700 2.32
0.99 10 1000 42.8
2.40 3 1000 15.8
2.20 1 1050 16.4
2.45 0.33 1000 1.02
2.80 0.66 1000 1.54
2.57 0.85 1010 12.8
2.22 0.66 1000 2.1
2.18 0.75 1000 2.5
2.07 + trace 0.75 1000 2.2
(CH )NH
2.45 0.83 1000 2.2


~pp"









times of twenty-four hours in the initial experiment of

heating (CH3)2DNBD3 with (CH3)2HNBH3 and of a time of one

hour in the experiments where just the initial reaction

products were desired in an attempt to ascertain a kinetic

isotope effect.

A trace of free dimethylamine added to one of the

reaction tubes did not significantly affect the extent of

reaction.

Hydrogen elimination on heating dimethylamine boranes

Dimethylamine borane was sublimed from a storage

flask into a reaction tube equipped with a capillary break-

off tip. The amount of compound sublimed into the reaction

tube was determined by weighing the storage bulb before and

after the sublimation. Then a second dimethylamine borane,

containing a different isotopic distribution of hydrogen

atoms on boron and nitrogen was sublimed into the reaction

tube, and the tube sealed off with a torch. In a typical

experiment, approximately one mmole of each compound was

used. The reaction tubes were heated at 100 + 20C for the

desired reaction time. After rapid cooling the non-con-

densible gas was transferred into a bulb by using the

Toepler pump. The gas samples were stored at room tempera-

ture until analysis in the mass spectrometer.

The results of these experiments were given in Table


13.













































,-4
0









Hff







O
SH




0





o





O

01


SON
0 0




*


.













r- ;K





0 OC
S *

















02 0














;CM









rC' cO
*












o









M


A- 0 0


o


'D H
*






L 0r\







A I
*!







00

_- O-






CO






















A L\O 0
I








fI0 0









-O
^-/







P1 L\ 0


ID OJ
(U 0
.















dLr ('
OC






*0 o
*
Lf\O
















*












SOO

0 HO
O C








a
O O
r^







^-^


cO 00

*


-t r
CO CO












I I
I I









COC



-4 r-*


N oP











m 00
N-

p 0 0
O
CO
/-l r- r-{





KN
+




- i
Q 00

OJ


do
a1) -H
0 -P
O
00



















0
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o








































0










0)






















o

5 9


0
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PC0


S
H-1 ON


p








CM


r1f
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u
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E- kD







HO
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CMC










HCM










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00








DO0
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Experiments to eliminate possibility of isotopic inter-
change during the elimination reactions

I. Heating of D2 and H2 in the presence of mercury

vapor.--A bulb was attached to the vacuum system, evacuated,

and submerged in a liquid N2 bath. After condensing mercury

vapor into the bulb for ten hours, approximately equal moles

of hydrogen and deuterium were placed in the bulb. The

bulb was closed and heated at 1000 for twenty-four hours.

The gas was analyzed by the mass spectrometer and shown to

be only hydrogen and deuterium. No exchange of the H2 and

D2 occurred under these conditions. Therefore, it was con-
cluded that the reaction gases did not exchange among

themselves, even in the presence of mercury vapor.

II. Heating D2 with (CH )2HHNBH3 and (CH )NBH3 to

determine if exchange occurred.--The amine borane was placed

in a tube with a capillary break-off tip, condensed in

liquid N2 and evacuated. Deuterium (150 mm) was placed in

the tube and the tube glass sealed. The tube was heated at

1000 for one hour and then a sample of the gas removed from

the tube by breaking the tip and allowing the gas to expand

into a bulb. The gas was analyzed in the mass spectrometer

to determine if any HD had been produced. The gaseous

product did not contain any material with a m/e of 3

according to the mass spectral analysis. The solid materials









were dissolved in spectral grade carbon tetrachloride and

the infrared spectra (Figures 17 and 18) determined. The
-1
spectra showed no absorption whatever at 1750-1800 cm ,

where BD absorbs intensely, but were identical to the

spectra of (CH3)2HNBH3 and (CH3)3NBH .

The experiments were repeated heating the deuterium-

amineborane mixtures for twenty-four hours. The infrared

spectra in both cases contained absorptions in the 1700-

1800 cm-1 range. The spectrum (Figure 19) of (CH3)2HNBH3

and D2 after heating had weak absorptions at 1725 and 1850

cm and an intense absorption at 1785 cm which is where
the BD stretching vibration occurs. The spectrum (Figure

20) of (CH3)3NBE3 and D2 after heating had a medium absorp-
tion at 1740-1750 cm1.
An infrared spectrum (Figure 6) was taken of

(CH3)2HNBH3 after thirty-four hours at 1000 and the spectrum
-1
had a medium absorption at 1750 cm This absorption must

be due to some reaction product and not to a BD vibration

since there was no deuterium in the molecule or in contact

with it. The absorption would cause an error in any esti-

mation of the absorption due to BD in this region. There-

fore, any calculations by Beer's law of the BD percentage,

after heating which considered the absorption in the 1750
-1
cm- region would be in error. The calculation would imply

a larger percentage BD than actually existed.










60



4)




\0 P- 0
0C\) 0


>C




co 7
C) 4-4


rc) E
10 Ic
E ~-.-



>) V) C
cz r4+
C~ cz a

o 5 ac)









cr







CH









_ _ _ _ _ _4-)
_0









cz)
4-I
r44
C)~
























OZ0 \0 +C.
quaoO
c c
k

4-4




C'-C





-~v N





















0
0
CN







0
0








O






0

O FO






o




N
C)






0














CO,
0
0
0
Cu\










0
0
OC








0
0
0
c\


a~~e3~rnsueJ~ ~ua~ Ja6
















O
O
O




1-I


0









O(




-O




0
\o E
0l o
O




0



0c >
i- (C








O













C\
(M


aou emsuej3. ;uqo ja









The infrared spectrum of (CH3)3 NBH3 was unaffected

by heating for twenty-four hours at 1000.

The data showed that exchange between dimethyl or

trimethylamine borane and deuterium did not occur in one

hour at 1000 but that exchange did occur after twenty-four

hours at 1000.

The data are summarized in Table 14.

III. Heating of (CH )2DNBH to determine if exchange

occurred between ND and BH within the molecule.--N-deutero-

dimethylamine borane was heated at 1000 for eleven hours in

a sealed glass tube.' The material was handled in the

vacuum system or in the Dri-Lab controlled atmosphere box.

The solid material was dissolved in spectral grade carbon

tetrachloride and an infrared spectrum (Figure 3) obtained.

This spectrum was compared to a spectrum of an unheated

sample of (CH3)2DNBH3 (Figure 2).

Beer's law was used to calculate the concentration

of compound containing NH, ND, BH, and BD using the CH de-

formation peak as the internal reference (see Table 3).

The spectra (Figures 2 and 3) showed an enrichment in the

percentage of deuterium contained in the unreacted material,

and a decrease in the percentage of hydrogen-containing ma-

terial. The concentration of NH containing compounds de-

creased from 22 per cent to 15 per cent, ND increased from





















cnO
CO 0
M )







04


F-P






o



CQ)

0





E-p



0







0





rd
0
0

















*


NI




















0


0


0
H
c)
v>



rc

ff

(\


CM


+ +


c(I


N


v>


UP
z



0


a)
bO
to
0

pq 0
F9 >S


0
0
0























0
0d
r4






LTt






rlX


r-i

0d
o 0



OH

p *aO4*
pQ

rl







4-






r\.
CM







Cj


0


H


COi
CM -


0


z

0
r<\


rC\
X
0
^/


I









78 per cent to 85 per cent, BH decreased from 97 per cent

to 92 per cent and BD increased from 3 per cent to 8 per

cent when the compound was heated. During heating, di-

methylaminoborane was formed, which had an absorption peak

in the same region (1750 cm-1) as the BD absorption. There-

fore, the absorption peak at 1750 cm- in the spectrum of

(CH3)2DNlBH3, after heating, could not be attributed solely

to BD containing compounds, and the calculation of 8 per

cent BD was an over-estimate. Any calculations or quanti-

tative considerations of this 8 per cent BD would be

questionable.

IV. Heating of (CH3)2DNBH3 and (CH )2HNBD to determine

if amine exchange occurred.--Dimethylamine borane-d3 and N-

deuterodimethylamine borane were sublimed into a tube equip-

ped with a capillary break-off tip, and the glass was sealed.

Duplicate tubes were heated at 1000 for twenty-four hours.

The non-condensible product was removed and analyzed

in the mass spectrometer (see Table 15). The solid products

also were analyzed in the mass spectrometer (Figure 21).

The experiment was dpne in duplicate. In neither

case did the mass spectra show a peak at the mass to charge

ratio of 65. The peak at this m/e would occur only if the

completely deuterated compound were present in the solid

material. If amine exchange occurred, then this peak would















--


o
Co











-o



-D
O^


-0


cn





-!
hO



--0 r
0
C) -






;fo
CH ;C


Q)
C.)






C) C
C:










cC
-0
c- Z
r^

c\


S r-i
b .





C vC

C)







O
4- <







cz

C)





C)







I



--
r0


==r6


3
3





--I

_I
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C)





x




C.)
-4

*r-1









be present; otherwise, the highest mass to charge ratio

would be 62, the parent ion peak for (CH3)2HNBD3. There-

fore, amine exchange does not occur under the reaction

conditions.

In the mass spectrum for (CH3)2 HNBD3, the ratio of

the intensities of peak 61:62 was 7.9. The mass spectra,

taken on the solid material after heating, contained a ratio

of the peak intensities of 61:62 of 5.4 and 5.8 for the two

experiments. In the recorded spectra, the peak at m/e of

62 was a shoulder on the peak at m/e of 61. The same base

line was used to get both peak heights. This may not be

the actual height of peak 62, but it may actually be less

intense than measured, which would tend to bring the ratio

of 61:62 more into line with that for the spectrum of

(C 3)2HNBD .











DISCUSSION OF RESULTS


Possibility of hydrogen-deuterium exchange

Every isotope study must be thoroughly checked to
make sure that an exchange process does not vitiate the

conclusions. Exchange between hydrogen and deuterium,

either in the gas phase or when bonded to other atoms with-

in a molecule, could invalidate the experiment. Therefore,

it becomes of primary importance to ascertain if any ex-

change reactions could occur under the experimental

conditions. Even a kinetic isotope effect in the hydrogen

elimination reaction would cause enrichment in the unre-

acted compounds of the less reactive isotope, and thus
affect the measured ratio of H2:HD:D2 from a long term

reaction. Therefore, the critical experiments to determine
the isotope effect were run for only 1 to 2 per cent hydro-
gen elimination to avoid this possibility.

There are five processes by which isotopic inter-
change could occur:

(a) H2+ D2 = 2 HD [6]
(b) (CH3)2HNBH3 + D2 = (CH3)2HNBH2D + HD [7]

(c) (CH3)2DNBH3 = (CH3)2HNBH2D [8]
(d) (CH 3)2HNBH + (CH )2DNBD =- (CH )2DNBH3

+ (CH3)2HNBD3 [9]









(e) Exchange between reactants prior to amineborane
formation. Each of these possibilities was
examined experimentally.

The mass spectrum of a mixture of D2 and H2 with

mercury vapor, heated for twenty-four hours at 1000, did
not contain a peak at m/e of 3. Therefore, exchange re-

action [6], even over mercury metal, did not occur.
Dimethylamine borane and trimethylamine borane were

heated with deuterium gas to determine if exchange occurred.
After one hour at 1000, neither (CH3)2HNBH3 or (CH 3)NBH3
had exchanged with the D2 gas. A mass spectrum of the gas

from the reaction tube showed no HD, and the infrared
spectrum of the solid materials showed no BD absorptions

in the 1750-1800 cm-1 region.
However, after twenty-four hours at 1000, both

(CH3)2HNBH3 and (CH3) NBH3 had exchanged to some extent with
the D2 gas, since their infrared spectra showed BD absorp-

tions in both instances.

The reaction products when dimethylamine borane was

heated were hydrogen gas and dimethylaminoborane, according

to the equation:

(CH3)2HNBH heat ) H2 + (CH3)2NBH2 [10]

At 1000, the dimethylaminoborane will disproportionate (7)

according to the equation:


5(CH3)2NBH2 = [(CH3)2N]2BH + (CH3)2NB2H5


[11l]









Noeth (31) has reported that (CH )4N2'2BH3 will give

(CH )2NBH2 and (CH )2HNBH3 when heated, and at 1000 the
principal product was (CH )NBH2 and H2 with some

[(CH3)2N]2BH and (CH3)2NB2H5 being produced. Therefore,
under the experimental conditions, the reaction products

would not be just hydrogen and the aminoborane, but a more

complicated mixture of compounds. Since aminodiborane is

known (6) to exchange with deuterium gas, the argument could

be made that it was this species or possibly the aminoborane
which was exchanging with the deuterium gas and not the

amine borane. But, the BH bonds in trimethylamine borane

exchanged with deuterium gas under the same conditions.

Therefore, it is not unlikely that exchange also occurred

between dimethylamine borane and D2 gas.

Deuterium gas has been reported to exchange also with

diborane (6,12,57) and with the BH bonds in borazine (10).

From the experimental data, it can be concluded that

exchange between deuterium gas and dimethyl or trimethyl-

amine borane did not occur to a measurable extent in one

hour at 1000, but that it did occur in twenty-four hours

at 1000. This result must be considered in the interpreta-
tion of the experimental results.

The intramolecular exchange (equation [8]) did not

occur when (CH3)2DNBH3 was heated. Since the starting

material contained some NH and BD bonds, the change in









relative concentrations in the infrared spectra, on heating,

had to be calculated using Beer's law. The change in NH

containing compound gave the more accurate resultsa and

indicated an enrichment of the deuterium containing compound

in the unreacted material. The enrichment in ND bonds, in

the material remaining after heating, implied that the NH

bonds were lost much more readily. A relative change in the

moles of NH to the moles of ND can be calculated from the

spectral data. If one considered the total moles of di-

methylamineborane, a, to be the sum of the moles of NH and

ND, then before heating there were 0.22a moles of NH and

0.78a moles of ND. Assuming that the reaction was 30 per

cent completeb according to equation [10], then 0.30a total

moles of both NH and ND reacted. After heating, the moles

of NH were (0.15) (1.00a-0.30a) which was 0.105a and the

moles of ND were (0.85) (1.00a-0.30a) which was 0.60a. This

corresponded to a decrease in moles of NH of 0.115a or 52.3

per cent and in moles of ND of 0.18a or 23.1 per cent.

These calculations indicate the following:

(1) A hydrogen atom was eliminated 2.3 times more
readily than a deuterium atom from the nitrogen.

(2) There was an increase in concentration of the

deuterium-containing compound in the unreacted material.


aSee page 16.

This figure should be reasonably accurate considering
the data in Table 12.










(3) Exchange between the ND and BH was not occurring

to any significant extent during the reaction time. Other-

wise, a greater decrease in ND would be expected and less

of a decrease or even an increase in NH would be expected

since there were 3 BH bonds per ND bond available for ex-

change in the original molecule.

The analogous calculation using the BD or BH absorp-

tions would contain too large an error to be meaningful.

Since ND and BH absorb in the same region, the BH absorption

could not be used for the calculation. The BD absorption

could be used, but to do so the following assumptions must

be made:

(1) The absorptivities ratio of BH:CH is the same as

that for BD:CH.

(2) The absorptivities of BH:CH in (CH3)2HNBH3 is the

same as that for BH:CH in (CH3)2NBH2.

The second assumption was checked by heating

(CH3)2HNBH3 for thirty-four hours at 1000 and then subliming
out the most volatile portion of the reaction mixture. The

infrared spectrum gave a ratio of absorptivity of BH:CH of

1.30 compared to that of 1.90 for (CH3)2HNBH3. The lower

value for the absorptivity ratio would cause an under-

estimation of the amount of BH compound actually present if

the value of 1.90 were used in the calculation. But, the








most significant point in this spectrum was an absorption

at 1750 cm-1. This absorption meant that a reaction product

also absorbed in the same region as the BD vibration. Thus,

an over-estimation would be made of the amount of BD con-

taining material in an infrared spectrum after the compound

was heated; the 8 per cent BD calculated from the spectrum

after heating was probably much greater than the actual

amount of BD.

Therefore, the experiment indicated that any intra-

molecular exchange between hydrogen and deuterium on heating

was insignificant.

To determine whether amine exchange occurred between

the amine borane molecules, N-deuterodimethylamine borane

and dimethylamine borane-d3 were heated at 1000 for twenty-

four hours. A mass spectrum of the solid materials did

not contain a peak at m/e 63 which would be present if amine

exchange had occurred to form N-deuterodimethylamine borane-

d3. The mass spectrum did show an intense peak at m/e 61

which had a shoulder at m/e 62. If (CH3)2DNBD3 had been

present a low intensity peak at m/e 63 and a more intense

peak at m/e 62 would have been expected. The intensity of

the peak at m/e 62 did not increase, therefore no amine ex-

change took place. Moreover, its intensity could be fully

accounted for by the presence of unreacted starting material.

Therefore it was concluded on this basis that amine exchange

did not occur.










However, the possibility of exchange between the

gaseous elimination products and the dimethylamine boranes

could account for the absence of the completely deuterated

amine borane. Even if amine exchange occurred to give

(CH5)2 DBDJ a subsequent reaction with H2 could conceivably

have reduced the parent mass peak to an undetectable level,

Thus, the above conclusion is open to some doubt.

The failure to prepare (CH )2DNBH3 and (CH )2HNBD3

in which there was not also an impurity of BD or ND bonds

implied that an exchange reaction was occurring before

adduct formation. The only other method to produce the

impurity would be an intramolecular exchange in the adduct,

but experimental evidence discounted this possibility even

when the adduct was heated.

The compounds were prepared by condensing diborane

and excess dimethylamine together and warming to -780 to

form the adduct. An exchange reaction must have occurred

at a rate comparable to the rate of adduct formations at

this temperature. Dahl and Schaeffer (10) have reported

that N-deuterodiethylamine exchanged with the BH bonds in

borazine at -300 within three minutes. Since the ND bond

in diethylamine exchanges with the BH bond in borazine, it

would be reasonable to expect that a NH bond in a secondary

amine could exchange with a BH bond in diborane. The

infrared analysis of'the dimethylamine boranes, prepared










from the amine and diborane, seemed to indicate that this

exchange did occur to some extent.

The preparation of (CH3)2DNBH3 from (CH )2ND2C1 and

excess LiBH4 contained even more BD bonds according to the

infrared spectrum than were present in the compound pre-

pared from amine and diborane. The infrared spectrum of

(CH3)2DNBH3 implied that 72.8 per cent ND bonds and 13.2

per cent BD bonds were present in the compound. The calcu-

lation was made from Beer's law using the CH deformation at

1475 cm-1 as the internal standard. The comparison of 13.2
per cent BD bonds to 27.2 per cent Na bonds indicated that

an exchange reaction occurred prior to the reaction to pro-

duce the amine borane. Otherwise, the per cent BD bonds

should be equal to the per cent NH bonds if the exchange

occurred after the amine borane was formed. If the exchange

reaction did occur before amine borane formation, as the

data implied, then the unreacted LiBH4 should have contained

some BD bonds.

N-deuterodimethylamine borane, prepared from the

amine and diborane, contained 3 per cent BD as compared to

13.2 per cent in the compound prepared from (CH3)2ND2C1 and
LiBH4. These data indicated that the exchange reaction be-

tween CH3)2TND2 and BH-4 occurred to a greater extent be-

fore adduct formation than was observed for the amine

diborane reaction.










Heating mixtures of dimethylamine boranes containing various
distributions of hydrogen isotopes for one hour

In order to determine if the kinetic isotope effect

in the elimination reaction could be attributed to the

nitrogen or boron-bonded hydrogen isotope, mixtures of di-

methylamine boranes were heated at 1000 for one hour. A

reaction time of one hour was used to minimize the reaction

extent so that the observed product compositions could be

related unequivocally to a known isotopic distribution in

the reactants. In each mixture, either the boron or nitro-

gen bond was one hydrogen isotope and the other hydrogen

bonds in that molecule and in the other molecules were the

other hydrogen isotope; for example, one mixture was

(CH )HNBD3 and (CH3)DNBD3. The isotopic distribution was

varied to determine if a NH or a ND bond was eliminated

more readily or whether a BH bond reacted more readily than

a BD bond.

The results in Table 15 show the following: (1) If

one molecule contained a NH bond, and the rest of the

hydrogen in the system was the deuterium isotope, then the

principal product was HD, the ratio of H2:HD:D2 being

0.15:1.00:0.39. (2) If one molecule contained ND bonds,
and the rest being the hydrogen isotope, then the principal

product was H2, the ratio of H2:HD:D2 being 4.75:1.00:0.0.

(3) If one molecule contained BH bonds, and the rest being









the deuterium isotope, then the principal product was HD,

the ratio of H2:HD:D2 being 0.52:1.00:0.67. (4) If one

molecule contained BD bonds, and the rest being the hydrogen

isotope, then the principal product was H2, the ratio of

H2:HD:D2 being 1.32:1.00:0.05.

The data implied that a hydrogen atom was eliminated

more readily than a deuterium atom since in each instance

the primary product was either H2 or HD and not D2, even

in the cases where there was only one NH or BH bond in the

system. The data were consistent with a BD bond being
eliminated more readily than a ND bond. In the experiments
which compare these two bonds, the H2:HD ratio was 4.75:1.00
for the ND case and 1.32:1.00 for the BD case. This implied
that HD was eliminated between a BD bond and a NH bond

approximately 3.6 times faster than between a ND bond and
a BH bond. The HD:D2 ratio of 2.56, when (CH3)2DNBD3 and

(CH3)2pHNBD3 were heated, compared to the HD:D2 ratio of

1.39, when (CH )2DNBD3 and (CH3)2DNBH3 were heated, indi-
cated that HD was eliminated between a BH bond and a ND

bond 1.84 times faster than between a NH bond and a BD bond.
The HD:D2 ratio of 2.56, when (CH3)2DNBD3 and

(CH )2EHNBD were heated, and the H2:HD ratio of 4.75, when

(CH3)2DNBH 3 and (CH )2HL\TBH3 were heated, indicated a large
kinetic isotope effect to be occurring when the hydrogen

isotope bonded to the nitrogen atom was varied. Thus, the








ratio of the rate constants for the nitrogen atom eliminating

Hk N
a hydrogen or deuterium atom experimentally determined,

varied between 2.7 and 4.8. Edwards (13) has predicted a

ratio of the rate constants for the bond breaking process in-

volving NH and ND bonds of 8.5. The average experi-
k \
mental isotope effect for the ) of 3.8 was less than the

predicted ratio of 8.5. This implied that there was con-
siderable, but not complete, loss of the NH stretching
vibration in the activated complex.
The HD:D2 ratio of 1.39, when (CH3)2DNBD3 and

(CH3)2DNBH3 were heated, and the H2:HD ratio of 1.32, when

(CH3)2HNBD3 and (CH3)2HINBH3 were heated, indicated a small
kinetic isotope effect to be present when the hydrogen
isotope bonded to boron was varied. Thus, the ratio of the
rate constants for the boron atom eliminating a hydrogen

or deuterium atom BH, experimentally determined, was
(BD /
1.3 to 1.4. Hawthorne and Lewis (17) calculated the ratio

of B )to be 4.2 for the expected effect of isotopic

substitution on boron from the loss of the BH stretching
vibration at 2300 cm-1. The observed isotope effect was
much less than that predicted, implying that there was only
a small loss of the BH stretching vibration in the activated
complex.









The maximum isotope effect would be obtained when

the bond to hydrogen or to deuterium was essentially com-

pletely cleaved in the activated complex, and the isotope

effect would decrease with increasing bonding in the

activated complex (44). Therefore, the isotope effects

observed should allow some predictions about a possible

configuration of the activated complex in the hydrogen

elimination reaction. The larger effect when ND was substi-

tuted for NH than when BD was substituted for BH predicts

that the NH(ND) bond was more affected in the activated

complex than was the BH(BD) bond. Hawthorne (17) has re-

ported a similar situation in the hydrolysis of pyridine

diphenylborane with water or deuterium oxide in acetonitrile

solution. The reaction was found to be first order in both

pyridine diphenylborane and water, and a primary kinetic

isotope effect was determined. The ratio of the rate

constants( -H of 6.90, when deuterium oxide was substi-
OD
tuted for water, was nearly as large as that predicted for

a complete loss of the OH stretching vibration in the

activated complex of 9.9. The ratio of the rate constants

H- of 1.52 observed on isotopic substitution on boron was
kBD B

much less than the predicted ~- )of 4.2 for complete loss
of the BH stretching vibration in the activated complex.
of the BH stretching vibration in the activated complex.









Hawthorne (17) proposed the transition state (I)

for the BH bond hydrolysis and suggested that this type of

non-linear transition state may be general for hydride

transfer.



O H
H- o '- -B- Py

C6H5 06H I


The similarity between the isotope effect observed

by HawthorneJand that observed here in the hydrogen elimina-

tion reaction of dimethylamine borane, suggests that the

reactions might be occurring through a similar activated

complex. Namely, that the activated complex was not a

linear configuration involving NH and BH bonds but that the

NH bond was stretched more along the bond axis than was the

BH bond, in a manner analogous to that for the OH and BH

bonds in I.

These data must be interpreted in the light of

possible exchange reactions occurring faster than the

elimination reaction. Since hydrogen and deuterium gas did

not exchange when heated for 24 hours at 1000, this possi-

bility could be discounted. If amine exchange between

boranes occurred, there would be no net change in the

systems, so this would not cause any difficulties. Deuterium









gas when heated at 1000 for one hour with dimethylamine

borane did not affect the infrared spectrum of the solid

material. Therefore, it may be concluded that no isotope

exchange reactions occurred during one hour at 1000, and
that the data were not subject to any uncertainties due to
exchange.
The starting materials were not as pure in their

isotopic distribution as would be necessary to determine a
precise kinetic isotope effect in the hydrogen elimination
reaction. The infrared spectra showed the following:

(1) (CH3)2DNBH3 contained 3 per cent BD bonds
relative to the per cent CH bonds.

(2) (CH3)2HNBD3 contained 7 per cent ND bonds
relative to the per cent CH bonds.

(3) (CH3)2DNBH3 contained 13 per cent BD bonds
relative to the per cent CH bonds.a (Prepared from

(CH3)2ND2+ and BH4-).
Compounds (1) and (2) were prepared by condensing
dimethylamine and diborane together and forming the adduct
at -78. Compound (3) was prepared from (CH3)2ND2+ and BH,-.
In each instance some exchange must have occurred before
the reaction producing the amine borane adduct.


aThis compound was not used in any of the hydrogen
elimination experiments.









The presence of isotopic impurities introduced

during synthesis would account for the D2 produced when

(CH3)2HNBD3 and (CH3)2HIHBH3 were heated and for the H2
produced on heating (CH3)2HNBD3 with (CH3)2DNBD3 and

(CH3)2DNBH3 with (CH )2DNBD3.
The data from the one-hour heating experiments did
not unequivocally distinguish between a unimolecular and

a bimolecular reaction mechanism. But, the analogy to

Hawthorne's work with the hydrolysis of pyridine diphenyl-

borane (17) and the large percentages of HD obtained in

each case does favor a bimolecular reaction. However, the

molecularity of the reaction was resolved by the experiment
in which (CH3)2DNBD3 and (CH3)2HNBH3 were heated.

Heating mixtures of dimethylamine boranes containing various
distributions of hydrogen isotopes for twenty-four hours

Dimethylamine borane and N-deuterodimethylamine

borane-d3, in 1:1 molar ratio, were heated at 1000 for

twenty-four hours and the non-condensible products were
analyzed in a mass spectrometer. If the hydrogen elimina-
tion reaction were unimolecular, then the gaseous product
should contain H2, D2 and perhaps some HD due to incomplete
deuteration. If the reaction were bimolecular, the gaseous
products should be H2, HD and D2 in the ratio of 1:2:1,
respectively, neglecting isotope effects.










The experimentally determined ratio of H2:HD:D2 was

3.8:4.3:1.0. The data implied that the reaction was bi-

molecular and that there was an isotope effect favoring H2

eliminations in the reaction.

Dimethylamine borane-d3 and N-deuterodimethylamine

borane, in a 1:1 molar ratio, were heated for twenty-four

hours at 1000 and the non-condensible reaction products were

analyzed in the mass spectrometer.a If the reaction were
unimolecular the gaseous product should be HD with the D2

and H2 due to incomplete deuteration. If the reaction were

bimolecular, the gaseous products should be H2, HD and D2

in ratio of 1:2:1 neglecting isotope effects.

The gaseous products had a H2:HD:D2 ratio of 3.1:3.6:

1.0. Since the gaseous products of the reaction contained

more H2 and D2 than could be accounted for by incomplete

deuteration, the reaction must have been bimolecular. The

data were in close agreement with the previous results and

indicated that it made no difference whether the deuterium

atoms were all in one molecule or partly on the nitrogen

in one molecule and partly on the boron in the other molecule.

The results in both cases gave the same percentages of H2,

HD and D2 in the gaseous product.

The total deuterium percentage in each of the re-

action systems, (CH3)2HNBH3 (CH )2DNBD3 and (CH,)pDNBH3 -

aFor mass spectral analysis of the solid reaction
products see Figure 21.









(CH3)2HNBD3, was almost the same. From the infrared spectra,
the system (CH )2DNBH3 (CH3)2HNBD3 contained 47.4 per

cent deuterium bonds and from the pyrolysis products of the

diborane-d6, the system (CH3)2HNBH3 (CH )2DNBD3 contained

a minimum of 45.4 per cent deuterium bonds. Therefore, it

was not surprising that under the same conditions, if the

reaction were bimolecular or if an equilibrium reaction

were established, for these two systems to give the same

ratio of H2:HD:D2 in the gaseous elimination products.

However, the interpretation of these results was made

questionable by the possibility that exchange occurred during

the reaction between deuterium and the reactants or other

reaction products. Some exchange did occur between di-

methylamine borane and deuterium gas on heating for twenty-

four hours at 1000, the same conditions as in these experi-

ments. In order for the two experiments to have had the

same ratio of H2:HD:D2 in the gas phase with exchange

occurring between the gases and other compounds in the

system, the reaction mixtures in each experiment must have
reached the same equilibrium.

Equilibrium would have been established according to
the following equations for the boron containing reaction

products (7).

[(CH )2NBH2]2 2(CH)2NBH2 [12]









3(CH3)2NBH2 = [(CH )2N32 BH + (CH3)2NIB2H5 [133

Burg (6) reported that the aminodiborane in the

presence of excess D2 after seventy-four hours at 1000 was
found to be 65 per cent deuterated. In experiments using

D2 gas to deuterate a compound, a large excess of D2 gas

and long reaction times were used to be sure an equilibrium

was established. In the hydrogen elimination reaction of

(CH )2DNBD3 and (CH3)2HNBH3, the per cent reaction was

31.3 per cent. Therefore, of the original 1.59 mmoles of
amine borane, there remained 1.09 mmoles unreacted amine

borane, with 0.50 mmoles of gas and 0.50 mmoles of amino-

borane produced. The 0.50 mmoles of gas contained 0.06
mmoles D2, 0.22 mmoles HD and 0.20 mmoles H2. If an exchange

reaction were occurring between the gaseous hydrogen iso-

topes and the boron-nitrogen compounds, then the ratio of

H2:D2 in the gaseous product should be the same as the ratio

of H2:D2 over any other catalytic system. Essentially the
boron-nitrogen compounds would be serving as a catalyst for
the hydrogen-deuterium exchange reaction, H2 + D2 = 2HD.
Considering the total moles of gas to be A, then the amount
of hydrogen gas available in the (CH3)2HNBH3 (CH3)2DNBD3
system would be 0.26A moles and of deuterium would be
0.24A moles. Using the equilibrium constant,3.48 at 4000K,
calculated by Urey (42) for the deuterium exchange, the

moles of HD were calculated to be 0.20A; and thus, the









concentration at equilibrium of H2 would be 0.08A and of

D2 was 0.06A. The ratio of H2:D2 at equilibrium would

therefore be 1.33. The observed ratio of H2:D2 was 3.53,

implying that the gaseous products were not at equilibrium
for the exchange reaction.

If an exchange reaction were occurring between the
gaseous hydrogen isotopes and the boron-nitrogen compounds,

then a consideration of the difference in zero-point energy

between a BH and a BD bond compared to the difference in H2
and D2 bonds should give an indication of the thermo-
dynamically favored reaction.

For two isotopes in an otherwise identical bond, the
difference between the two zero-points of energy is given
by E = h(--Vi), where V and )/ refer to bonds containing
the lighter and heavier isotopes X and X', respectively.
The difference inVUBH and 1BD calculated from only the
stretching vibrations at 2550 cm-1 (BH) and 1875 cm-1 (BD)

was 1.36 kcal/mole, and the difference in HH and~)DD
calculated from the frequencies for the fundamental vibra-
tion transitions (1) of 4159 cm-1 (HH) and 2990 cm-1 (DD)
was 3.34 kcal/mole. Thus, a comparison of the differences
in zero-point energies indicated that the reaction to pro-
duce D2 would be thermodynamically the most favored and the

gas phase should be enriched in D2. This was contrary to
the observed kinetic isotope effect and the observed ratio










of 41.3 per cent H2:47.7 per cent HD:11.0 per cent D2 in

the gaseous product.

Therefore, it does not appear likely that the ex-

change reaction between H2, HD or D2 and the amine boranes

or aminoboranes had reached equilibrium in twenty-four

hours at 1000. The exchange reaction, thus, has only a

secondary effect on the eliminated gases and the reaction

must be bimolecular as was inferred by the experiments on

heating the dimethylamine boranes for one hour.












CONCLUSION


The reaction of dimethylamine borane to eliminate

hydrogen was bimolecular and a kinetic isotope effect

occurred during the elimination of hydrogen. The data

showed that a hydrogen atom was eliminated faster than a

deuterium atom and that a BD bond reacted more readily than

a ND bond.

The ease and speed of deuterium and hydrogen atoms

exchange limits many of the possible experiments which

might be used to elucidate the behavior of the dimethylamine

borane system on heating, and in studying the kinetic iso-

tope effect in the reactions of the amine boranes. More

work needs to be done to establish the conditions and

possibly the rates of the deuterium-hydrogen exchange re-

action in the BN containing compounds. A case in point

being R. E. Davis' report (11) that the rate of deuterium

exchange in acidic D20 with trimethylamine borane was much

more rapid than the hydrolysis reaction. In this work,

evidence was presented that for N-deuterodimethylamine

borane-d3, the rate of exchange with acidic H20 was approxi-

mately equal or only slightly faster than the rate of

hydrolysis. This inferred a possible order of magnitude for

the rate of the exchange reaction.




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