Synthesis and structure of the first pentacoordinate thiasiliranides

Pentacoordinate thiasiliranides, K+, 18-crown-6, [{C6H4-2-C(CF3)2O}SiPh{CH(CH2-t-Bu)S-}]− were synthesized by deprotonation of the corresponding α-mercaptoalkylsilanes, {C6H4-2-C(CF3)2O}SiPh{CH(CH2-t-Bu)SH} with KH in the presence of 18-crown-6. X-ray crystallographic analysis of cis-thiasiliranide showed an exceptionally small SiCS angle (87°) as a result of significant intramolecular Si–S interaction. Hydrolysis of the pentacoordinate thiasiliranides gave 2,2-dimethylbutanethiol, while the reaction with HCl afforded the α-mercaptoalkylsilanes.