Tris(trimethylsilyl)sulfonium and Methylbis(trimethylsilyl)sulfonium Ions:  Preparation, NMR Spectroscopy, and Theoretical Studies¹

Abstract

Tris(trimethylsilyl)sulfonium 1 and methylbis(trimethylsilyl)sulfonium 2 ions were prepared as long-lived species by reacting trimethylsilane and trityl tetrakis(pentafluorophenyl)borate (Ph(3)C(+) TPFPB) in the presence of precursor sulfides and characterized by (1)H, (13)C, and (29)Si NMR spectroscopy at -78 degrees C. Attempted preparation of dimethyl(trimethylsilyl)sulfonium ion under similar conditions failed as a result of the formation of the more stabilized trimethylsulfonium ion. Structures, and (13)C and (29)Si NMR chemical shifts were calculated by density functional theory (DFT)/IGLO methods. The calculated results agree well with the experimental data.