Exhaustively Trichlorosilylated C_1 and C_2 Building Blocks: Beyond the Mueller-Rochow Direct Process

摘要

The Cl~(–)-induced heterolysis of the Si–Si bond in Si_(2)Cl_(6) generates an [SiCl_(3)]~(−) ion as reactive intermediate. When carried out in the presence of CCl_(4) or Cl_(2)C═CCl_(2) (CH_(2)Cl_(2) solutions, room temperature or below), the reaction furnishes the monocarbanion [C(SiCl_(3))_(3)]~(−) ([A ]~(−); 92%) or the vicinal dianion [(Cl_(3)Si)_(2)C–C(SiCl_(3))_(2)]~(2–) ([B ]~(2–); 85%) in excellent yields. Starting from [B ]~(2–), the tetrasilylethane (Cl_(3)Si)_(2)(H)C–C(H)(SiCl_(3))_(2) (H_(2)B ) and the tetrasilylethene (Cl_(3)Si)_(2)C═C(SiCl_(3))_(2) (B ; 96%) are readily available through protonation (CF_(3)SO_(3)H) or oxidation (CuCl_(2)), respectively. Equimolar mixtures of H_(2)B /[B ]~(2–) or B /[B ]~(2–) 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_(2) furnishes the disilylethyne Cl_(3)SiC≡CSiCl_(3) (C ; 80%); in the presence of [HMe_(3)N]Cl, the trisilylethene (Cl_(3)Si)_(2)C═C(H)SiCl_(3) (D ; 72%) is obtained. Alkyne C undergoes a [4+2]-cycloaddition reaction with 2,3-dimethyl-1,3-butadiene (CH_(2)Cl_(2), 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 (CH_(2)Cl_(2), 180 °C, 4 d). All closed-shell products were characterized by ~(1)H, ~(13)C{~(1)H}, and ~(29)Si NMR spectroscopy; an EPR spectrum of [n Bu_(4)N][B ~(• )] was recorded. The molecular structures of [n Bu_(4)N][A ], [n Bu_(4)N]_(2)[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 ]~(2–), C , and D are postulated.