Exhaustively Trichlorosilylated C and C Building Blocks: Beyond the Müller-Rochow Direct Process.

The Cl-induced heterolysis of the Si-Si bond in SiCl generates an [SiCl] ion as reactive intermediate. When carried out in the presence of CCl or ClC═CCl (CHCl solutions, room temperature or below), the reaction furnishes the monocarbanion [C(SiCl)] ([A]; 92%) or the vicinal dianion [(ClSi)C-C(SiCl)] ([B]; 85%) in excellent yields. Starting from [B], the tetrasilylethane (ClSi)(H)C-C(H)(SiCl) (HB) and the tetrasilylethene (ClSi)C═C(SiCl) (B; 96%) are readily available through protonation (CFSOH) or oxidation (CuCl), respectively. Equimolar mixtures of HB/[B] or B/[B] quantitatively produce 2 equiv of the monoanion [HB] or the blue radical anion [B], respectively. Treatment of B with Cl ions in the presence of CuCl furnishes the disilylethyne ClSiC≡CSiCl (C; 80%); in the presence of [HMeN]Cl, the trisilylethene (ClSi)C═C(H)SiCl (D; 72%) is obtained. Alkyne C undergoes a [4+2]-cycloaddition reaction with 2,3-dimethyl-1,3-butadiene (CHCl, 50 °C, 3d) and thus provides access to 1,2-bis(trichlorosilyl)-4,5-dimethylbenzene (E1; 80%) after oxidation with DDQ. The corresponding 1,2-bis(trichlorosilyl)-3,4,5,6-tetraphenylbenzene (E2; 83%) was prepared from C and 2,3,4,5-tetraphenyl-2,4-cyclopentadien-1-one under CO extrusion at elevated temperatures (CHCl, 180 °C, 4 d). All closed-shell products were characterized by H, C{H}, and Si NMR spectroscopy; an EPR spectrum of [ nBuN][B] was recorded. The molecular structures of [ nBuN][A], [ nBuN][B], B, E1, and E2 were further confirmed by single-crystal X-ray diffraction. On the basis of detailed experimental investigations, augmented by quantum-chemical calculations, plausible reaction mechanisms for the formation of [A], [B], C, and D are postulated.