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An experimental investigation of the reactions of alkyl-tin compounds with boron compounds.

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An experimental investigation of the reactions of alkyl-tin compounds with boron compounds.

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Content AN EXPERIMENTAL INVESTIGATION OF THE
REACTIONS OF ALKYL-TIN COMPOUNDS
WITH BORON COMPOUNDS
by
JOHN RUSSEL SPIELMAN
A Thesis Presented to the
FACULTY OF THE GRADUATE SCHOOL
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
MASTER OF SCIENCE
(Chemistry)
June 1958
UMI Number: EP41619
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....................... -.....JOHN-O-JGOOKE........
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Date..... J.una.,... 19.5.8. ............................
Faculty Committee
airman
c
A C K N O W L E D G M E N T
The author wishes to express appreciation to
his research director, Dr. Anton B. Burg, for
helpful advice on the experimental work and con
structive criticism of th is manuscript.
The generous financial support by the Office
of Naval Research is also gratefully acknowledged.
TABLE OP CONTENTS
C H A P T E R
I. IN T R O D U C T IO N ....
I I . E X P E R IM E N T A L M E T H O D S
Apparatus ....
Reagents ........................
Analysis .......................
I I I . T H E R E A C T IO N S O P S O D IU M T R IM E T H Y L T IN W IT H
B O R O N L E W IS A C ID S ...... ...................................
Reaction of Sodium Trimethyltin with
Trimethylboron in Liquid Ammonia . . . . .
Reactions of Sodium Trimethyltin in Diethyl
Ether . . ......................................................................................
Reaction with Boron Trifluoride ..............................
An Attempt to Prepare (C H ) SnB(CH ) . . .
3 3 3 2
Interpretation of the Boron Chemistry of
Sodium Trimethyltin . . . . . . . . . . . .
.
I IV. T H E R E A C T IO N S O P H E X A M E T H Y L D IS T A N N A N E . . . .
I
Methylation of Boron Trifluoride . . . . . .
Acid Catalyzed Rearrangement of Hexamethyl-
distannane .......................................................................................
V. SUM MARY....................................' ..................................................................
B IB L IO G R A PH Y ....................... ..................................................................................
LIST OF TABLES
T A B L E
I. The Catalytic Disproportionation of Hexamethyl
distannane at 1 0 0 ° C. .......................
C H A P T E R I
IN T R O D U C T IO N
The chemistry of carbon-boron compounds is well
known, but attempts to produce compounds containing boron
bonded to other Group IV elements have been few and largely
unsuccessful. T w o such attempts w ill be reviewed.
Smith and Kraus^ attempted the reaction
3( C6 H 5)3GeNa d- BC13 — » [( CgH g) gGe] 3B - V - 3NaCl
in diethyl ether. They obtained a product which analysis
showed had the correct B to G e ra tio for C (C H ) GeD_B, but
6 5 3 5
i t could not be purified.
o
Gibbins trie d the reaction of potassium dibutyl-
boron, KB(n-C^Hg)g, with bromosilane. The main products
which he could identify were silane, potassium bromide and
tributylboron. Also, he obtained a red gum m y m aterial for j
which he reports the hydridi.ec*; hydrogen, to silicon, to I
boron ratio 1.56:2,00:3.25. H e suggested the structure: |
I
|
(1) P. B. Smith and C. A. Kraus, J. A m . Chem. Soc., 74. !
1418 (1952). !
(2) Sidney Gore Gibbins, Ph. D. D issertation, University!
of Washington, 1955, p. 11. j
However, his resu lts are inconclusive and no evidence for 1
I
the structure was given. j
5
i
N o record was found in,the lite ra tu re of an attempt *
i
to synthesize a tin-boron compound and study its properties.]
•2 h
Sodium trim ethyltin, which was discovered by Kraus, offers ]
' i t
s
a possible route to such a compound. I t acts as an electron]
i
donor in liquid ammonia as shown in the following examples: ]
( C H ) _ S n V H+ — > ( CH_) _SnH
3 5 3 5
- i
(C H ) Sn • + • RBr — > (CH,).,SnR + Br~ I
5 3 3 0 j
(C H3 )3 Sn“+ [RgSnNH^ — * R3 SnSn(CHg)3 + N H g. \
Compounds are known in which R stands for methyl, ethyl, j
S
n-propyl, or phenyl groups, and many others are possible.
These reactions would be expected of such an ion. j
i
Som e polyhalides react in a different way. According-
i
1
j
(3) C. A. Kraus and W . V. Sessions, J. A m . Chem . Soc., 47,s
2364 (1925). — j
4
to Kraus, Carbon tetrachloride reacts with sodium t r i
methyltin to give sodium chloride and hexamethyldistannane
in nearly one hundred per cent yield. H e did not determine
5
what happened to the carbon atom. Kraus and Neal suggest
the following series of reactions for chloroform:
3(CH5 )sSn"-t- C H C 15 — » [(GH^SnTgCH SCI-
[(CH3 )3 Sn]3C H — > [(C H 3 )3 Snlg (.C H 3 )3 SnC B =C H Sn(C H 3)
. . . . . . • - i
Only the fin al products could be isolated* However, methy-!
lene chloride reacts as follows: |
!
2NaSn(CH3) 3 -f C H 2 Clg — > [( CH^SnlgCHg -t- 2NaCl j
• !
j
Ethylene dichloride gives ethylene and [(CH3)3Snlg again. j
I t appears, therefore, that a single carbon atom can hold I
' !
no more than two tin atoms and tin atoms on adjacent carbon j
atoms sp lit off hexamethyldistannane. j
6 |
Kraus and Sessions noted that sodium trim ethyltin j
' \
Is unstable at room temperature and at 70° C. decomposed 1
I
\
rapidly into methane, tetram ethyltin, and sodium tin alloy, i
I
In the course of th is work i t has been found that i t started
I
i
i
(4) C. A. Kraus and A. M . Neal, J. A m . Chem. Soc., 52, I
|4426 (1930). — - j
I (5) Ibid. |
| . . . \
! • ' *
j (6 ) Kraus and Sessions, loc. c it. I
4
giving off methane-at ahout -20° C. and decomposed fairly
fast at room temperature giving in addition to the above
mentioned products a small amount (1 0 ^ based on tin) of
hexame thyldi s tannane.
The purpose of this work was to find out whether
(C H ) Sn“ would act as an electron donor toward som e boron
o o
Lewis acids in liquid ammonia and diethyl ether. For exam
ple one might expect the reaction in liquid ammonia:
i
( C H 5) 3 B N H 3 -t~ (C H 3) 3 Sn~ — > (C H 3) gBSii( C H 3) 3~ - V - N H 3 I
3
\
This situation is sim ilar to that for the strong base,
7
Na H B(CH_) , discovered by Burg and Campbell which forms a
2 0 2 |
stable adduct with (C H ) B in liquid ammonia. Na HB(CH„)_ j
o o 2 5 2,;
is a hydride donor in dimethyl ether rather than an electron
donor, but one would expect NaSn(CH,)~ s t i l l to be an
5 5 j j
K
electron donor in diethyl ether unless i t could give up a j
I
C H 3” group. \
Boron triflu o rid e in ether would be expected to \
|
give an adduct, Na^ [(CH,*)_SnBF_] which would lose NaF to
o o o
give (CH^JgSnBFg. O n the other hand, two or more (CH^JgSn
I
jmight add to B F3 with displacement of F” and then s p lit off |
J[(CH_)_Snl as in the carbon tetrachloride reaction. ,
I O w 2 i
A less extensive series of reactions might be j
• l
\
(7) A. B. Burg and G -. W . Campbell, J r ., J. A m . Chem. Soc.,s
74, 3744 (1952).
5
expected if dimethylboron fluoride were added to an ether
solution of NaSn(CH ) . One would expect the (C H ) Sn“
3 3 3 3
to replace the fluoride ion and stop there:
NaSn(CH3 )3 +'(CH3> B F - - - -» NaF - + • (CH'^SnBfCHgJg.
I t was hoped then that (C H ) SnB(CH ) would be stable and
3 3 3 2
vo latile enough to bdvstudied easily in the high vacuum
apparatus.
Since hexamethyldistannane, [(CH^) ^Snj ^, is involved
in this work i t is worth-while to review the work concernirjg
8
i t . This compound was also discovered by Kraus w ho mis
takenly thought from molecular weight determinations at the!
boiling point of benzene that i t contains a high concentra-
Q
tion of (C H } Sn radicals. However, Selwood showed by
3 3
magnetic measurements that i t could.not be more than 2 per
cent dissociated. In liquid am m onia^ i t reacts with sodium:
2Na + [(C H ) S n ~ J —► 2NaSn(CH )
3 3 2 3 3
According to K raus^ the following occurs with sodium amide::
[(C H 3 ) 3 Sn] 2 -f- N aN H g —> ( C H 3 ) gSnN H g + ( C H 3) 'SnNa.
Although the compound (CH,)„SnNH is supposedly vo latile i t
3 3 2
(8 ) C. A. Kraus and W . V. Sessions, J. A m , Chem. Soc., 473
2361 (1925).
(9) H. Morris and. P. W . Selwood, J. A m . Chem. Soc., 63,
2509 (1941). ,
(10) C. A. Kraus and A. M . Neal, J. A m . Chem. Soc., 52,
695 (1930).
6
was not isolated! hence the reaction is not verified. Other
1 1
reactions given by Kraus and Sessions are;
[(CH3 ) 3 S n l 2-*- drOg — » UCH3 ) 3S n ] 20
at room temperature without solvent
S >
[(CH3)3Snl2+ S — ♦ [CCH3)3Sn]2S
in benzene at room temperature; and
12 !
in benzene. Kozeschkov gives the reaction of a sim ilar |
compound, [(CgHg)3 Sn3g, with diphenyl mercury at 160° C. j
> ' ' ’ I '
for seven hours: j
[(C2H 5)3Sn^2 + 2(C2H 5)5SnC6H 5 + Hg* j
ii
I t may be seen that the f(0H )_Snl molecule can react under^
3 < 5 j
rather mild conditions and the tin -tin bond is the weak j
i
point which, with the possible exception of the reaction \
s
with sodium amide, breaks symmetrically. j
I
The purpose of this work then was as follows: j
1. To study the electron donor properties of the j
i
trim ethyltin anion toward boron Lewis acids in ammonia and
diethyl ether.
2. To determine whether stable compounds containing-
t
i
|
j
(11) Kraus and Sessions, loc. e it. j
|
(12) K. A. Kozeschkov, A. N. Nesmejanow, and W . P. !
Pusyrewa, Ber., 69, 1639 (1926). !
tin-boron bonds could b © made from the resulting coordina
tion compounds.
3. To investigate the reactions of hexamethyl-
distannane with these acids.
C H A P T E R II
E X P E R IM E N T A L M E T H O D S
Sine© essen tially the sam e experimental technique
was used throughout this work, a chapter w ill be devoted to
describing i t in general and to give the methods of analysss
used. |
|
Apparatus j
J
In addition to the usual laboratory equipment, a
high vacuum line was used to handle not only the v o latile ;
boron compounds but also som e of the tin compounds. The j
liquid ammonia solutions were made up in a large te s t tube |
I
which was fitte d either with a siphon to tran sfer the ;
liquid to a f r itte d glass f i l t e r or with a ground jo in t with
which to seal i t to the vacuum lin e. W hen an ether solution
i
was to be filte re d , the apparatus consisted of a large j
i
lambda tube with a stopcock and ground jo in t so i t could be i
I
I
i
removed from the vacuum line without opening. The reactants
were placed In one leg, and the other leg had a fritte d
|
glass disc. The solution was filte re d by tipping the tube ;
and allowing the solution to run onto the f i l t e r disc. j
|
Reagents !
Starting m aterials were eith er purified commercial j
9
products or prepared according to the methods given in the
standard works on organometallic compoundsHowever, i t
might be worthwhile to discuss the preparation of three com
pounds which involved special techniques.
Dimethylboron fluoride, (CH,,)0 BF, was prepared ac-
o (Z
2
cording to the following sequence given by Burg and Banus:
(CH3 ) 3B-V (CH3 ) 2NH —» (GH3 )gBN(CH3 ) -hCH
(ch3 )2 bn(ch3 )2 4-bf3 — » (ch3 )2 bf-+- (ch3 )2 nbf2
\
The calculated amounts of trimethyl boron and d ime thy 1 amine
!
were sealed into a heavy walled tube and heated to 300° C. ;
5
and 3 atm. pressure. The tetramethylaminoborine was puri- 1
fled by high vacuum d is tilla tio n . Then equi-molar quanti- ]
I
tie s of tetramethylaminoborine and boron triflu o rid e were !
condensed in a large reaction tube, warmed slowly to -78.5°]
o ^
C., and then warmsd rapidly to 0 C. The dimethylboron •
fluoride was then purified by fractio n al condensation until!
3
i t showed a vapor pressure of 93 m m . at -78.5° C. !
1
i
(1) (a) E. Krause and A. von Grosse, "Die Chemie der {
M e tall-organ! schen Verbindungen," Gebrueder Bomtraeger, \
Berlin, 1937, p. 194. !
' \
(b) G. E. Coates, VOrgano-Metallic Compounds," J. \
Wiley and Sons. Inc., N ew York, N. Y., 1956, pp. 55-72. \
i
(c) J. G. A. Luigten and G. J. M . van der Kerk, j
"Investigations in the Field of Organ©tin Chemistry," Tin
Research In s titu te , Greenford, 1955, pp. 85-94. i
i
(2) A. B. Burg and J. Banus, J. A m . Chem. Soc., 76, 3903 I
1(1954). — [
10
The usual method of preparing hexamethyldistannane
3
which is given by Kraus, involves purification of the pro
duct by washing with water, drying with sodium sulfate, and
d is tillin g under reduced pressure. This process is d i f f i
cult and wasteful because the hexamethyldistannane is
oxidized by the a ir fa irly fa s t. However, i t was found that
i t could be efficie n tly purified by high vacuum d is tilla tio r
since i ts vapor pressure at room temperature is about 1.5
m m . Therefore, the reaction j
2( CHg)gSnCl 2 Na — * ftCHg^Snlg -t 2N aC -l j
J
was performed in liquid ammonia with a slight excess of I
' - ' ' ' I
sodium. The ammonia was sublimed off at -78° C. leaving j
the hexamethyldistannane and sodium chloride. The hexa- |
*
methyldistannane was then fractio n ally condensed in a trap j
at about -20° C. The pure product melted sharply at 23.5°C.;
. ¥ ■ '
j
I t was necessary to prepare sodium trim ethyltin justj
before i t was used. In th is work two routes of preparation
were employed. The f i r s t was to drop tetram ethyltin slowly
into a solution of sodium in liq u id ammonia:
2Ha + (GH_) .Sn H - H H — > NaSri(CH„)_ + N aN H C H ,
3 4 3 3 3 2 4
The insoluble sodium amide was removed by filte rin g the i
i
(3) C. A. Kraus and W . V. Sessions, J. A m . Chem . Soc., !
47, 2364 (1925). j
1 1 1
f
solution into another te s t tube or the lambda tube described
in the section on apparatus. The second method was to
charge a reaction tube with the proper amounts of sodium
and trim ethyltin chloride, and then condense in enough
ammonia to dissolve them and le t the reaction
2Na (CH^SnCl — » NaSn(CH3)3 NaCl
take place. Usually the sodium ehloride did no harm, so i t
I
was not removed. j
I
5
ii
i
Analy sis \
Tin was determined by wet washing with a mixture of
n itr ic acid and sulfuric acid according to the method givenj
!
4 5
by Gilman and King. The solution was evaporated u n til ■
sulfur trioxide fumes came off and then dissolved in warm 6 j
I
normal hydrochloric acid. The tin was reduced to the +2 ;
I
state with granulated aluminium and titra te d with 0.1 normal
•
5 j
iodine solution according to the method given in Scott. j
i
Fluoride was determined photometrically from the j
bleaching of the orange zirconium^o-sulfohydroxy-dimethyl- j
6 *
jfuehsine-di carbqxyla te . I
r *
! t
t
I '
j (4) H. Gilman and W . B. King, J. A m . Chem. Soc., 51, 1213'
(1929). I
! I
j (5) W . W . Scott, ’ 'Standard Methods of Chemical A nalysis,” ■
jN . H. Furman, editor, Vol. I, F ifth edition, D. Van Nostrandj
jCompany, In c., N ew York, N.Y., 1939, pp. 964-966. !
j (6) S. Megregian, Anal. Chem., 26, 1161 (1954). j
CHAPTER I I I
T H E R E A C T IO N S O P S O D IU M T R IM E T H Y L T IN
W IT H B O R O N L E W IS A C ID S
An attempt was made to form a stable adduct of
(C H ),Sn” and any of the Lewis acids trimethylboron,
3 3
dimethylboron fluoride, or boron triflu o rid e . A reaction
was carried out between trimethylboron ammoniate and sodium
trim ethyltin in liquid ammonia to determine whether the
(CHg)gSn" would displace the ammonia from trimethylboron.
This displacement would be expected to occur since (CH_)„Sn‘
3 3 i
J
seems to be a stronger base than ammonia. Sim ilar reactions5
' ‘ ■ ' |
were carried out in diethyl ether between sodium trim ethyl- j
i
tin and eith er dimethylboron fluoride or boron triflu o rid e , i
j’
Reaction of Sodium Trime th y ltin with Trimethylboron in j
Liquid Ammonia
A slight excess of trimethylboron ammoniate (3.90
mmole) was added to a solution of sodium trim ethyltin (2.85
ranole) in liquid ammonia at -35° C. There was no apparent
j
change in the solution. The ammonia was removed at -78° C.,j
t
and the mixture was slowly warmed to about 10° C. During |
i
jthis period a small amount of methane and nearly a ll of the !
jtin as hexamethyldis tannane were evolved. The hexamethyl- j
jdistannane was id en tified by its melting point (25.5° C .) j
.1 3
2 5
and density (1.55^ g /cc.). W hen the mixture was warmed to
90° C. a larger amount of methane (3.8 mmole) and some more
hexamethyldistannane were evolved. W hen the methane had
ceased to com e off, the to ta l methane amounted to 4.21
mmole and the hexame thyldistannane, 1.30 mmole. This le f t
a solid, non-volatile residue of composition B ) _
• 00 w *L 2
Sn or nearly B(CH^)^. To form methane, a methyl group
probably extracts a hydrogen atom from an ammonia molecule.|
1
refore, the residue would include sodium amide,-possibly!
j
jcombined with som e methylated form of boron. j
i ;
! For further investigation of th is residue, gaseous
|
H C 1 was added in excess; this would be expected to destroy j
the sodium amide and release the methylated boron compound, j j
j
However, the residue yielded trimethylboron (0.38 mmole), j
methane (0.50 mmole), hydrogen (0.59 mmole), trim ethyltin !
jj
chloride (0.15 mmole) and a small amount of a liquid mixture!
which could not be purified. The color changed from brown j
to white during this treatment. F inally, water and hydrogen
i
chloride were added and the mixture heated to 98° C. fo r sijd
I
j
hours. This treatment should have yielded a mixture of |
:CH_B(0H)o and (CH„)oB 0H (composition was now B, _(CH_), _). i
J -. O o l . o j
However, only 0.71 mmole of C H B(O H ) could be recovered. j
o &
Although* the p o ssib ility of* boron-nitrogen bonding is not |
eliminated, these resu lts indicated there must be strong j
jboron-boron bonding in the solid residue.
1 4
Reactions of Sodium Trimethyltin in Diethyl Ether
I t would be d iffic u lt to work with (GH„) B P in llqv
3 2
uid ammonia since i t ammonolyzes easily. Boron triflu o rid e
forms an ammoniate which acts as a proton donor. Hence i t
would be less complicated to try to form an adduct of
NaSn(CH )„ with these acids in a more in e rt solvent such as
\ 3 3
diethyl ether. Sodium trim ethyltin is slig h tly soluble in
ether.
i
|
Reaction with Boron Trifluoride ;
In a typical experiment, 3.7 mmole of NaSn(CH_)_ l
3 3 I
was prepared in liq u id ammonia from tetram ethyltin. The j
solution was filte re d into the lambda tube described in
Chapter II which was then sealed to the vacuum lin e . The !
|
bulk of the ammonia was sublimed away at -78° C., and then I
j
the tube was warmed to -25° C. I t was pumped for two more j j
5
o ^
hours at -25 C. in an attempt to remove the la s t traces of!
ammonia. However, i t was impossible to remove a ll of i t , I
j
so excess BF„ (6.31 mmole) and several m illilite rs of ether!
5 - ■ 1
were condensed in a t -196° C. j
?
Reaction occurred as the mixture warmed to 0° C., ;
\
I 5
giving a white precipitate and a yellow solution. The \
|
solution was filte re d through the f r itte d glass disc in the!
!
other leg of the lambda tube. Evaporation of the ether i
l e f t a yellow-orange solid. Both of these products were j
I
evidently impure since analyses for tin and fluorine gave !
varying resu lts for several different experiments. The tin j
content of the yellow m aterial ranged from 22 to 45 per cent
and the fluorine from 10 to 15 per cent. Since the material
seemed to be polymeric, ether probably accounted for the
variation in composition. One sample had composition of 45
per cent tin and 15 per cent fluorine, implying a tin to
fluorine atomic ratio of 1:2.1. The white solid, which was
soluble in water, contained no tin and ranged in fluorine
j
content from 41 to 62 per cent. I t may, therefore, have j
j
been a mixture of sodium fluoride and boron triflu o rid e
i * i
ammoniate (45.2 and 67.2 per cent respectively). !
Small and varying amounts of hexamethyldistannane I
jj
were found in the reaction mixture when boron triflu o rid e
\
was not added in excess. Hence, i t was supposed that the j j -
j(C H ) Sn3 might be an intermediate in the reaction. A i
3 3 2 i
subsequent experiment showed that B F_ does react with hexa-l
5 \
methyldistannane. The reaction is discussed in d etail in j
Chapter IV. j
A n Attempt to Prepare (C H ) SnB(CH ) j
_ _ _ _ _ ________ __ ________ 3 5 • 3 2
A n analogous experiment was performed with dimethyl -j
boron fluoride in an attempt to prepare ( C H ) SnB(CH ) . i
3 3 3 2 '
To an ether solution of NaSn(CH ) (3.72 mmole) was added I
3 3 j
1.31 millimole of (CH^)gBF. Since the only substances I
wanted were (C H 3)3SnB(CHg)2 and NaF, only the v o latile j
1 6
products were separated. They were (CBLj^Sn (0.14 mmole) -
3 4
and [(CH_)_Snl (0.33 mmole; 0.663 mmole of tin ). The fact
3 3 2
that the number of millimoles of tin recovered as
[(CH )„Sn3 is nearly equal to half that of (C H ) B F is
3 o 2 3 2
fortuitous, since in another experiment in which 0.67 m m ole
V s 1
of (C H jj^ISF was used, 0.32 mmole of [{CH„)^Snlrt was found.
In te rpr e ta t ion of the Boron Chemistry of Sodium Trime thyltin
Although no evidence has been given here for a
j
stable compound containing a tin-boron bond, in the reaction
*
of sodium trim ethyltin and trimethylboron in liquid ammoniaj
* ' • ’ !
an adduct must form as an intermediate because there is no \
\
other logical way to explain the effect of ( C H )_Sn” on j
3 3 j
trimethylboron ammoniate. I f the ammoniate had donated a j
£
proton, as might be expected, i t would form trim ethylstan- j
i
nane which would easily be detected In the volatile pro- j
ducts. Even i f the trimethylstannane had reacted with
something else in the solution, a t least a small amount of
|
i t should have been recovered. Therefore, the course of
I
the reaction must have been as follows: j
j
(1) Sn(CH3)- + (CH3)3BNH3 -* NH3+ ( CH^SnBf CH^’ |
(2) (C H 3)3SnB(CH3)“ H - N H 3-> i[(CH3)3Sn]2 j
(C H ) B + C H + ■ N H “ !
3 2 4 2 j
Since most of the methane was evolved a fte r the hexamethyl
distannane, i t would be reasonable to assume that the
decomposition of the (C H 3)3SnB(CH3)3“ involves some
1 7
intermediate which might be represented stoichiom etricly
as (C H 3)3B“ .
Compounds sim ilar to the (C H ) B residue have been
3 2
reported in the lite ra tu re before. Kraus and Auten^ pre
pared something with:.the formula reported A s (C4H g)gB, by
treating dibutylboron chloride with sodium-potassium alloy
in diethyl ether. They did not study the properties fu r
ther except to note that i t was probably polymeric and on j
evaporating the ether i t disproportionated into trib u ty l- j
boron and polymeric (C^H^B) . I
* 4 9 x <
j
Unfortunately no definite conclusions can be drawn |
j
from the reactions in ether. They do not show any definite
j
stoichiometry probably because not a ll of the ammonia could
i
be removed from the system, and in trying to get rid of the]
1
ammonia some of the sodium trim ethyltin may have decomposed!
!
Furthermore, the products which were obtained could not ef-j
fectively be purified. There is an indication, however, j
j
that one of the main products may be hexame thyldistannane ]
\
in each case. Boron triflu o rid e might be expected to give i
j
]
this product by analogy to carbon tetrachloride and chi or o-:
|
forni, but what becomes of the boron is not apparent. Di
methylboron fluoride might give sodium fluoride and the j
i
i
)
(1) C. A. Kraus and R. W . Auten, J. A m . Chem. Soc., 74, '
3396 (1952). j
expected (CH,)„SnB(CH_)0 which breaks up into hexamethyl-
o O & C >
distannane and the (CH^J^B residue found in the case of
trime thylboron and sodium trim ethyltin in liquid ammonia;
I
however, the stoichiometry © f the reaction does not tend to
support th is idea. At any rate if a tin-boron compound is
formed in eith er of these two reactions, i t is very un
stable .
j
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CHAPTER IV
T H E R E A C T IO N S O P H E X A M E T H Y L D IS T A N N A N E
M e thylatIon of Boron Trifluoride
Since hexamethyldistannane seemed to be involved
in the reactions of sodium trim ethyltin with boron t r i -
fluoride, i t was suspected that hexame thyldistannane might
ji
react with boron triflu o rid e . Hence, 0.154 millimole of j
hexamethyldistannane and 0.535 millimole of boron tr if lu - j
oride were condensed in a tube which was sealed off and !
3
j
brought to about 10° C. A yellow solid slowly deposited j
on the walls of the tube. The reaction seemed complete in
»
*
about a day. 1 The tube was opened into the vacuum line and j
\
0.170 mmole of gas taken off. After fractio n al d is tilla - |
i
tion i t showed a molecular weight of 62.4 and a vapor pres-j
sure of 67.5 m m . at -97.7° C. [
W hen the same reaction was done on a larger scale, !
som e tetram ethyltin was produced, with a correspondingly j
i
I
lower yield of the above gas, but enough of the la tte r was j
obtained to establish the identity as methylboron d iflu - j
oride. A run involving 1.096 mmole hexamethyldistannsine i
i
and 2.699 mm ole boron triflu o rid e yielded 0.756 mmole of 1
|
methylboron difluoride, 0.780 mmole of tetrsunethyltin, and !
1.118 mmole of boron triflu o rid e . The methylboron j
20
difluoride was id en tified by vapor pressure (22.1 m m . at
-110.7 and 72.1 m m . at 97.1° C.; calculated 21.1 m m . and
71.8 m m . respectively)"^ and molecular weight (62.8; calcu
lated 63.8).
Although this reaction is not always quantitative
the stoichiometry approaches the equation
[(CH3 ) 3 S n l 2 + 2BF3 OH3BE2 + (CH3 ) 5 Sns BF4 ,
since in both experiments the amount of methylboron1 d i-
fluoride is nearly half the amount of boron triflu o rid e <
! |
j used up. The (C H ) Sn B P represents only the composi- j
* 3 5 2 4
tion of the residue, but since i t was yellow, i t may very j
likely be a mixture of polymeric dimethyltin (which is j
I
yellow) and (C H )_SnBF.. N o attempt was made to prove what
3 3 4 >
was in this mixture since the primary aim of the experiment
was to find out i f hexamethyldistannane was being produced |
I
in the e a rlie r reaction and then undergoing further re- !
I
action, which evidently is the case. Whether tetramethyl- i
i
tin is produced or not seems to depend on the conditions of
the reaction and possibly the presence or absence of som e !
impurity. j
j
Acid Catalyzed Rearrangement of Hexamethy1distannane |
Neither dimethylboron fluoride nor diborane re- j
\
acted with hexamethyldistannane at room temperature. This |
I
fa c t probably indicates that a very strong Lewis acid is I
required for the tran sfer of a methyl group.
21
However, at 100° C. the tin compound was converted
to tetram ethyltin and a m ethyl-tin polymer in the presence
of eith er dimethylboron fluoride or diborane. These Lewis
i
acid catalysts were recovered unchanged, except for some
pyrolysis,of the diborane. They were necessary for the
conversion, for hexame thyldistannane is unchanged when
heated at 100° C. The experiments are summarized in Table
I. Probably this type of reaction is also occurring in the
case of boron triflu o rid e in competition with the methyl
(
jgroup . transfer reaction, thus accounting for the nonstoichio-
! '
metric production of tetram ethyltin.
TABLE I
TH E C A TA LY TIC DISPROPORTIONATION O F
H E X A M E T H Y L D IST A IW A N E A T 100° G.
\
[ t® 3) 3Sn]2 ( ch3)2bf
B2»6
Time
V o latile
Components
Composition
of Residue
0,113 mmole.
— —
3B h rs. [(CH^) ^Sn] 2 * • 0.111 mmole.
—
0.122 mmole. 0.131 mmole. 36 h rs. [(CH3)3Snl2 : 0.020 mmole.
(C H j.Sn: 0.124 mmole.
3 4
(CH3)2BF: ' 0.131 mmole.
^C V l ,45Sni .00
0,330 mmole. 0.565 mmole. 1 hr.J (CH„).Sn: 0.459 mmole.
3 A
B ^ : 0.491 mmole .*
H„: 0.062 mmole.*
|^3^0-.22Sn1.00
* 13 per cent p y ro ly sis expected fo r B0H A a t T O O C. J
O k i!
K > \
CHAPTER V
S U M M A R Y
A n attempt has been made to demonstrate the elec
tron donor property of (C H ) Sn“ In liq u id ammonia and di-
3 3
ethyl ether toward boron Lewis acids. I t displaces ammonia
■ j
in trimethylboron ammoniate to form an adduct in liquid j
i
ammonia. The adduct decomposes below room temperature to i
i
!
give hexame thyldistannane and a residue which decomposes j
i
further into methane and a solid of empirical composition i
(CH_)0B. This residue is apparently not decomposed by
3 2
hydrochloric acid and water at 98° C.
Sodium trim©thyltin reacts with boron triflu o rid e
in ether to give a yellow polymeric solid and a white j
I
sa lt-lik e solid. Since boron triflu o rid e was in excess, j
!
th is evidently was the resu lt of the in itia l formation of !
hexamethyldistannane which subsequently reacted with the
\
boron triflu o rid e to give methylboron difluoride and the i
1
yellow solid. j
i
j
The reaction of sodium trim ethyltin with dimethyl- ]
\
|
boron fluoride failed to yield the compound (C H ) SnB( C H ) . j
3 3 32 j
Evidently i f i t is formed, i t decomposes into hexame thyl- S
!
distannane and some other non-volatile product. s
j
Hexamethyldistannane reacts with boron triflu o rid e j
24
at 10° c. to give a non-volatile yellow solid and eith er
methylboron difluoride or tetram ethyltin. In the presence
(
of dimethylboron fluoride or diborane at 100° C. i t rear
ranges to give tetram ethyltin and a methyltin polymer.
In the lig h t of th is work, therefore, the tin-boron
bond is unstable, not necessarily because the bond is weak,
but because i t can turn to something more stable. Thus at
lower temperatures the tin seems to go into hexamethyl- j
'
distannane rather than losing methyl groups. With boron
triflu o rid e and at higher temperatures, the boron-tin bond j
1
is not only unstable, but methyl groups can move around i
j
forming tetram ethyltin and methyl-tin polymer. j
More work needs to be done with the (CH,,)0B re si duel
O 2 !
Apparently there must be strong boron-boron or boron- ]
nitrogen bonding of som e kind to account for i t s inertness j
toward hydrochloric acid. Its so lu b ility and molecular
i
weight in various solvents might also be tested to give in
formation as to its state of aggregation and structure. |
j
Hexamethyldistannane is probably worthy of further j
•- i
study. The non-volatile products of its reaction with j
boron triflu o rid e should be investigated, as well as its 1
s
reaction with other strong Lewis acids such as boron |
|
trich lo rid e. i
|
I
t
BIBLIOGRAPHY i
j
J
I
1
I
j
i
i
\
I
I
B IB L IO G R A PH Y
A. B O O K S
Coates, G, E. Qrgano-metall1c Compounds. N ew York:
J. Wiley and Sons, In c., 1956.
Krause, E. and von Grosse, A. Die Chemie der m etall-
organis chen Ver bindungen. Berlin: Gebrueder Born-
traeger, 1937.
Luigten, J. G . A. and van der Kerk, G. J. M . Investigations
in the Field of Organotin Chemistry. Greenford: Tin
Research InstTTuteJ 1955.
Scott, W . W . Standard Methods of Chemical Analysis, Editor
N. H. Furman, Vol. I, F ifth Edition. N ew York: D. Van
Nostrand Company, 1939.
B. U N P U B L IS H E D M A T E R IA L
Gibbins, Sidney Gore. ’ ’The Reactions of Silane with Tri-
ethylzincate Anion and Dibutylborate (I) Anion.”
Unpublished Doctor’s D issertation, University of
Washington, 1955.
C. PER IO D IC A LS
Burg, A., B., J. A m . Chem. Soc. , 62:2228, (1940).
Burg, A. B. and Banus, J. J. A m . Chem. Soc. , 76:3905 (1954)
Gilman, H. and King, W . B. J. A m . Chem. Soc., 51:1213
(1929). ~ — --------- - - - - - -
Kozeschkov, K. A-., Nesmejanow, A. N., and Pusyrewa, W . P.
Ber. , 69:1639 (1936).
Kraus, C. A. and Auten, R. W . J. A m . Chem. Soc., 74:3398
(1952). - — ——- -- - - - -
Kraus, ,C . A. and Neal, A. M . _J. A m . Chem. Soc., 52:695 tlf/e
(1930).
Kraus, C. A. and Meal, A. M .
(1930).
Kraus, C. A * and Sessions, W .
47:2364 (1925).
Megregian, S. Anal. Chem. , 2
Morris, H. and Selwood, P. W . J.
(1941).
Smith, P. B. and Kraus, C. A. J.
(1952). “
2 7
J. A m . Chem. Soc. , 52:4426
V. J. A m . Chem. Soc. ,
:1161 (1954).
A m . Chem. Soc. , 63:2509
A m . Chem . Soc. , 74:1418
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Asset Metadata

Creator Spielman, John Russel (author)

Core Title An experimental investigation of the reactions of alkyl-tin compounds with boron compounds.

Contributor Digitized by ProQuest (provenance)

Degree Master of Science

Publisher University of Southern California (original), University of Southern California. Libraries (digital)

Tag chemistry, inorganic,OAI-PMH Harvest

Language English

Advisor Burg, Anton B. (committee chair), Adamson, A.W. (committee member), Brown, Ronald J. (committee member)

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