Cl--induced heterolysis of the Si-Si bond in Si2Cl6 generates an [SiCl3]- ion as reactive intermediate. When carried out in the presence of CCl4 or Cl2C═CCl2 (CH2Cl2 solutions, room temperature or below), the reaction furnishes the monocarbanion [C(SiCl3)3]- ([A]-; 92%) or the vicinal dianion [(Cl3Si)2C-C(SiCl3)2]2- ([B]2-; 85%) in excellent yields. Starting from [B]2-, the tetrasilylethane (Cl3Si)2(H)C-C(H)(SiCl3)2