Tris (Dimethylamino) sulfoniumcyclopentadienide [TAS]~+ [C_5H_5]~- and TRis (dimethylamino)-sulfoniumpyrrolide [TAS]~+ [C_4H_4N)~-: Two Isostructural Salts with 'Naked' Anions A~- and the 'Inverse' Sandwich-Cations [{Me_2N)_3S}_2A]~+ (A=C_5H_5~-, C_4

摘要

The cleavage of Si—C bonds by Bu_4NF or similar organic fluorides serves to remove Me_3Si protective groups with subsequent formation of C—H bonds. Intermediates in these reactions are highly reactive carbanions. which, under the reaction conditionschosen, can abstract protons from neighboring molecules. Particularly suitable for the cleavage of Si—element bonds is "TAS-fluoride" (tris(dimethylamino)sulfonium difluorotri-methy(silicate) [(Me_2N)_3S]~- [Me_3SiF_2]~- (1), which is readily availablein HF-free form: the chemical behavior of the fluoro-silicate ion corresponds to that of a "naked" fluoride ion. From the reaction of TAS-fluoride (I) with C_5H)5SiMe_3 (2) in CH_3CN at -40 deg C. the TAS salt 3 can be isolated in high yield as a reddish solid [Eq. (a)].