Different fluoride anion sources and (trifluoromethyl)trimethylsilane: molecular structure of tris(dimethylamino)sulfonium bis(trifluoromethyl)trimethylsiliconate, the first isolated pentacoordinate silicon species with five Si–C bonds

(Trifluoromethyl)trimethylsilane, CF3SiMe3 reacts with [(Me2N)3S]+[Me3SiF2]–, Q+F– and Q+[HF2]– (Q+ = Me4N+, [(Me2N)3C]+, [(Me2N)4P]+) at –70 to 50 °C to afford the first hypervalent silicon species, [(CF3)2SiMe3]– with five Si–C bonds (stable in monoglyme up to –10 °C) as the main reactive species whose molecular structure was determined by X-ray crystallography.