Stannylium borates

Stannylium borates 105[B(C6F5)4] (Scheme 32) [92]. These results indicate that in general the silylation of heavy carbene analogues using silylium ions or stabilized silylium ions is a promising route to the corresponding cationic species [93]. 

Much research has been carried out in many contexts to create anions with low nucleophilicity. In the specific context of low valent silyl cations, the anion families that have proved most successful have been perfluoroaromatics introduced by Lambert and Zhang and carboranes introduced by Reed and coworkers, reported in adjacent publications in 1993. Prior to use of these anions, unsuccessful investigations were reported with anions such as perchlorate, tetrafluoroborate, tetraphenylborate, and hexachloroantimonate. All successful preparations of stannylium cations have used perfluoroaromatic anions, particularly tetrakis(pentafluorophenyl)borate (TPFPB). 

In a subsequent study, Lambert, Herber, and their coworkers reported, by Mdssbauer spectroscopy, that the motion of the tin atom within tris(2,4,6-triisopropylphenyl)stannylium tetrakis (pentalluo-rophenyl)borate is isotropic. ... 

Silyl-substituted stannylium ions have been accessed by reaction of aryl-substituted stannylenes Ar2Sn with silylarenium borates. Stannylenes SnH2 and germylene GeH2 have been stabilized by the combination of an NHC donation to their vacant orbital and coordination via their lone pair to tungsten pentacarbonyl. ... 

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