RESEARCH
N e w Organomefallics, N e w Uses Applications include organic therapy, a n d oxygen removal ACS NATIONAL MEETING Organic Chemistry These n e w organ ometallic com pounds may latch on to long, useful lives: • Vinyllithium, a G r i g η a r d-1 i k e chemical that may help in synthesizing still other orgnnometallics which c a n t be made via conventional Grignard routes. • N e w water soluble organometallic chemicals with possible chemotherapeutic uses. • Silicon substituted boranes; poten tial oxygen scavengers in silicone fluids. Successful preparation of vinyllithium by Dietmar Seyferth and Michael A. Weiner at Massachusetts Institute of Technology followed t h e failure of all past attempts to make the com pound. Seyferth told the symposium on organometallic chemistry, held b y the Division of Organic Chemistry, that past efforts relied on techniques nor mally used to get alkyl- and aryllithium reagents. But now, thanks t o the commercial availability of tetravinyltin, vinyllithium can b e made bv an exchange reac-
synthesis,
chemo-
tion between phenyllithium and vinyltin c o m p o u n d s . Resulting tetraphenyltin precipitates almost quantitatively, while vinyllithium stays in solution. Yields of vi»> iliihium lange from 30 to 7 5 ' < . According t o Seyferth. vinyllithium "nicely c o m p l e m e n t s " vim lmagnesium bromide and chloride, which are Grig nard reagents. Another plus: Prepara tion of vinyl O r i g n a r d s is restricted to special solvents like tet rah ydrofu rani and tetrahydropyran. Such isn't the case with t h e new material, h e says, since the reaction can b e carried out in diethyl e t h e r or in hydrocarbon sol vents. Since organolithium compounds are more reactive than analogous Grignards, Seyferth expects a wide use of vinyllithium in both organic and in organic chemistry. Reactions t h a t may b e especially suitable include synthe sis of physiologically active compounds and preparation of vinyl-metal com pounds not possible via other routes. • New a n d W a t e r Soluble. These compounds c a m e from Seyferth*s and Samuel O. G r i m ' s study of effects that phosphonium has on an adjacent metaUcarbon bond. Reacting metallic and organometallic halides with phosphinemethylenes, says Seyferth, leads to water soluble organic derivatives of
many metals. T h e reaction is general and can he used to evaluate thtese c h e m i c a l s for c h e m o t h e r a p e u t i c activ ity. A typical example calls for reacting triphenylphosphinemethyiene with trimeth> lbromosilane. T h e product is a silicon substituted phosphonium salt with t h e tongue-twisting name of triphenyltrimethylsilylmethyiphosphonhim bromide. T h f metal-onrhon bond in such salts cleaves easily. Appar ently, says Seyferth, the b o n d is stable in acidic* water or alcohol solutions but decomposes to phosphonium cation in neutral or alkaline solutions. Many phosphutiiium ion derivatives (tetraphenylborate, for instance) can be m a d e this w a y . Studying the effects of metals on olefinic bonds is what led to the silicon substituted boranes. Seyferth hydrobora ted (with sodium borohydridc and a l u m i n u m chloride) trimcthylvinylsilane to get a triorganoborane— ( C H : i ) 3 SiC.»H4 ) ;iB—in 65 to 75'',< yields. Us ing triniethylamine borane as the bo ron h y d r i d e source raises t h e yield to around 90 f.i. T h e compound and s o m e analogs react slowly with oxygen to a c c o u n t for t h e oxygen scavenging property. O t h e r research in metal effects on unsaturation d o n e by Seyferth and Norbert Kahlen involves oxymercuration of a n olefin in which a vinyl g r o u p is l i n k e d to a metal group. Reacting trimethylsilane gives a mercury deriv ative wiiich can b e reduced to a n organosilicon alcohol.
TlV"ee^||l^nee«l: -ΡΐφΜ©ss. i n OrganofnetaSlics
42
C&EN
APRIL
2 0,
1959
