Tris(trimethylsilyl)sulfonium and methylbis(trimethylsilyl)sulfonium ions:Preparation, NMR spectroscopy, and theoretical studies

Tris(trimethylsilyl)sulfonium 1 and methylbis(trimethylsilyl)sulfonium 2 io ns were prepared as long-lived species by reacting trimethylsilane and trit yl tetrakis(pentafluorophenyl)borate (Ph3C+ TPFPB) in the presence of precu rsor sulfides and characterized by H-1, C-13, and Si-29 NMR spectroscopy at -78 degreesC. Attempted preparation of dimethyl(trimethylsilyl)sulfonium i on under similar conditions failed as a result of the formation of the more stabilized trimethylsulfonium ion. Structures, and C-13 and Si-29 NMR chem ical shifts were calculated by density functional theory (DFT)/IGLO methods . The calculated results agree well with the experimental data.