THE REACTION OF TETRAMETHYLSILANE WITH BORON TRIBROMIDE

Main Group Metal Chemistry Vol. 24, No. 01, 2001

THE REACTION OF TETRAMETHYLSILANE WITH BORON TRIBROMIDE

Jaroslaw Lewkowski*

and Michel Vaultier

Department of Organic Chemistry, University of Lodz, Narutowicza 68, 90-136 Lodz, Poland ~ Synthese et Eiectrosynthese Organique, U M R 6510 associe au C N R S , Universite Rennes 1,

F-35042 Rennes cedex, France

A b s t r a c t . T h e r e a c t i o n of t e t r a m e t h y l s i l a n e with boron t r i b r o m i d e in d e u t e r o c h l o r o f o r m in a m b i e n t temperature or at 4 0 ° C led to bromotrimethylsilane (3) and to d i b r o m o m e t h y l b o r a n e (4). Identity of products was c o n f i r m e d by N M R s p e c t r o s c o p y . Analogical reaction carried out in 1 , 3 - d i c h l o r o p r o p a n e a l l o w e d to separate products of the reaction and to obtain them in 6 8 % and 5 9 % yields respectively.

Key words: Tetramethylsilane, boron tribromide, bromine replacement, d i b r o m o m e t h y l b o r a n e

T e t r a m e t h y l s i l a n e is known as a stable compound and for this reason this reagent is c o m m o n l y used as an internal r e f e r e n c e in N M R spectroscopy. However, there are s o m e e x a m p l e s of its reaction catalysed by aluminium chloride1 , 2 to give chlorotrimethylsilane.

T h e a n a l o g u e of tetramethylsilane - tetramethylstannane reacts more easily with h a l o g e n a t i n g agents. S o m e papers have been published, which described various aspects of its reaction with boron t r i b r o m i d e , which g a v e dibromomethylborane.3"5 Aryltrimethylstannanes w e r e claimed to react with boron trichloride to

yield dichloromethylborane.6'7 T h e synthesis of d i b r o m o m e t h y l b o r a n e f r o m silyl c o m p o u n d w a s reported

only once from boron tribromide and tris-(trimethylsilanyl)amine.8

To our best knowledge, there are no examples for the reaction between tetramethylsilane and boron trihalide. L i t e r a t u r e r e p o r t s s o m e s u c c e s s f u l a t t e m p t s of t h e r e a c t i o n b e t w e e n a r y l t r i m e t h y l s i l a n e s9 , 1 or

vinyltrialkylsilanes" and boron trihalides to give aryl- or vinylhaloboranes respectively.

In this paper, we would like to report the first example of the reaction between tetramethylsilane and boron tribromide providing bromotrimethylsilane (4) and d i b r o m o m e t h y l b o r a n e (3) in fair yields. T h e reaction is a possible n e w method for synthesis of dibromomethylborane.

T h e reaction between tetramethylsilane (1) and boron t r i b r o m i d e (2) was carried out directly in the N M R tube in d e u t e r o c h l o r o f o r m at room temperature for several days. A f t e r a o n e day of storage, N M R analysis showed the formation of two new c o m p o u n d s and, after 5 days, the reaction was complete. ' H N M R signals appeared at δΗ= 0 . 5 8 and - 2 . 8 ppm, l 3C N M R - at 5C=4.13 and ( - 0 . 6 2 ) ppm. " B N M R and 2 9Si N M R

gave resonances at δΒ= 6 2 . 9 5 ppm and at 5Si=27.2 ppm respectively.

T h e s e data allowed to characterize products f o r m e d . A c c o r d i n g to Ralph and L a n d u c c i1 2 as well as to an

N M R data compilation1 4, bromotrimethylsilane 3 gives 'H N M R signal at δΗ= 0 . 5 8 ppm, 2 9Si N M R signal at

5si=26.5 ppm, 1 C N M R shift value is q u o t e d " '1 3 to occur at 5c=4.6 ppm.

Our N M R m e a s u r e m e n t s of post-reaction mixture showed 5H=0.58 ppm, 5Si=27.2 p p m and 5C= 4 . 1 3 p p m , so

v a l u e s so c l o s e to p u b l i s h e d o b s e r v a t i o n s that they s h o w u n d o u b t e d l y that o n e o f t w o p r o d u c t s is bromotrimethylsilane 3.

T h e second c o m p o u n d , w h i c h in our opinion is d i b r o m o m e t h y l b o r a n e 4, g a v e a ' H N M R signal at δΗ= -2.9

ppm, l jC N M R signal at 8C= -0.62 ppm and a " B N M R resonance occurred at δΒ= 62.95 p p m .

B \ , B r f CI (CH2)3CI B rs , B r f ®

ρ + M e — ^ i - M e — — ρ + M e — ^ i ~ B r

Br M e M e M e

1 2 3 4

S c h e m e 1

A d c o m p i l a t i o n1 5 as well as Nöth et at quoted a nB N M R chemical shift δΒ= 62.5 ppm, w h i c h fits perfectly

with our observation. S o m e disagreement with literature data appeared in the case of the 'H N M R resonance, w h i c h a c c o r d i n g to N ö t h4 a p p e a r s at δΗ= - 1 . 4 2 ppm in CCI4. O u r m e a s u r e m e n t s w e r e p e r f o r m e d in

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J. Lewkowski and M. Vaultier

The Reaction ofTetramethylsilane with Boron Tri bromide

d e u t e r o c h l o r o f o r m and this might be a reason for the difference observed. As for N M R , we found no data in the literature for carbon chemical shift of dibromomethylborane.

W h e n the reaction w a s carried out at 4 0 ° C , it was completed within 36 hours. Products w e r e separated by fractional distillation, but as boiling points of deuterochloroform ( b p = 6 0 . 9 ° C )1 6 and d i b r o m o m e t h y l b o r a n e

( b p = 5 8 - 6 0 ° C )8 are very close, w e obtained a mixture of these t w o c o m p o u n d s . B r o m o t r i m e t h y l s i l a n e w a s

isolated as the last fraction boiling at 79-81°C (lit'6=79°C).

W h e n the reaction w a s carried out in 1,3-dichloropropane, the separation of the products w a s much easier as the solvent boil at higher temperature. Dibromomethylborane was isolated by fractional distillation, collected at 59-61°C in 5 3 % yield. Bromotrimethylsilane was isolated as above in 6 8 % yield.

Y i e l d s are m a y b e not satisfactory, but the reaction provides useful reagents starting f r o m c h e a p starting materials.

Experimental section

D e u t e r o c h l o r o f o r m (Merck), tetramethylsilane (Fluka) and boron tribromide (Aldrich) w e r e used as received. I , 3 - D i c h l o r o p r o p a n e w a s routinely distilled and dried prior to use. All N M R spectra w e r e r e c o r d e d on a Brucker 300 A C spectrometer.

Reaction between tetramethylsilane (1) and boron tribromide (2) in d e u t e r o c h l o r o f o r m

T e t r a m e t h y l s i l a n e (89 mg, 1 m m o l ) was dissolved in deuterochloroform (3 m L ) and then boron t r i b r o m i d e (25 mg, 1 m m o l ) w a s added. T h e reaction w a s stored for 5 days at room temperature or heated at 4 0 ° C for 36 hrs. T h e p r o g r e s s of the reaction w a s m o n i t o r e d by 'H and nB N M R s p e c t r o s c o p y . T h e m i x t u r e w a s

separated by distillation, first fraction was collected at 59-61°C. It was the solution of d i b r o m o m e t h y l b o r a n e 4 and deuterochloroform.

Reaction between tetramethylsilane (1) and boron tribromide (2) in 1,3-dichloropropane

T e t r a m e t h y l s i l a n e (89 mg, 1 m m o l ) was dissolved in 1,3-dichloropropane (3 m L ) and then boron tribromide (25 mg, 1 m m o l ) w a s added. T h e mixture was stirred under nitrogen for 5 days. T h e n , the m i x t u r e w a s s e p a r a t e d by f r a c t i o n a l d i s t i l l a t i o n . T h e first f r a c t i o n w a s c o l l e c t e d at 5 9 - 6 1 ° C and i d e n t i f i e d as d i b r o m o m e t h y l b o r a n e 4. The second fraction, bromotrimethylsilane 3, w a s collected at 79-81°C.

Bromotrimethylsilane 3

Yield 68%. Bp. 79-81°C, lit16 79°C, nD=1.4235, lit16 1.4240.

' H N M R (300 M H z , CDC13): δ 0.52 (CH3). I 3C N M R (75 MHz, CDCI3): δ 4.13 (CH3). 2 9Si N M R (59 M H z ,

CDCI3): δ 27.3.

D i b r o m o m e t h y l b o r a n e 4.

Yield 5 9 % . Bp. 5 9 - 6 1 ° C , lit8 5 8 - 6 0 ° C . 'H N M R (300 M H z , CDC13): δ -2.9 (CH3). I 3C N M R (75 M H z ,

CDCI3): δ -0.62 (CH3). " B N M R (96 MHz, CDCI3): δ 62.95.

A c k n o w l e d g e m e n t . Authors wish to thank Dr. Sourisak Sindbandhit ( C R M P O - Rennes) for his assistance in recording of N M R spectra.

References and notes:

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4. Nöth, Η.; V a h r e n k a m p , Η. J.Organomet.Chem., 1968, 12, 23 5. Gerrard, W.; Mooney, E.F.; Rees, R.G. J.Chem.Soc., 1964, 740 6. Chivers, T.; David, B. J.Organomet.Chem., 1968, 13, 177 7. C h a m b e r s , R.D.; Chivers, T. J.Chem.Soc., 1965, 3933 8. Barlos, K.; Noeth, H. Chem.Ber., 1977, 110, 3460

9. Haubold, W.; Herdtie, J.; Gollinber, W.; Einholz, W. J.Organomet.Chem., 1986, 315, 1 10. Gross, U.M.; Bartels, M.; K a u f m a n n , D. J.Organomet.Chem., 1988, 344, 217

I I . Mikhail, I.; K a u f m a n n , D. J.Organomet.Chem., 1990, 398, 53 12. Ralph, J.; Landucci, L.L. J.Org.Chem., 1983, 48, 3884

13. Breitmeier, E.; Voelter, W. Carbon-13 NMR Spectroscopy, VCH, Weinheim 1989, 293

14. Harsmann, H.

Si NMR Spectroscopic Results in Oxygen-17 and Silicon-29 NMR, NMR Basic

Principles and Progress series (Ed Diehl, P.; Fluck, E.; Kosfeld, R), Springer Verlag 1981, 202

15. Nöth, H.; Wrackmeyer, B. Nuclear Magnetic Resonance Spectroscopy of Boron Compounds, NMR

Basic Principles and Progress series (Ed Diehl, P.; Fluck, E.; K o s f e l d , R), S p r i n g e r Verlag, 1978, 1 3 2 , 3 7 2

16. Aldrich Catalogue of Fine Chemicals 1999-2000, 285, 392

Received: N o v e m b e r 8, 2000 Accepted: November 30, 2000

-A c c e p t e d in publishable format: November 31, 2000

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