α,ω-oligosilyl dianions and their application in the synthesis of homo- and heterocyclosilanes

The reactions of bridged tris(trimethylsilyl)silyl fragments with 2 molar equiv of potassium tert-butoxide allow the generation of alpha,omega-oligosilyl dianions (1a, 2a, 3a, 4a). Depending on the nature of the spacer between the oligosilyl units, these compounds can be used to generate either linear or cyclic derivatives. They are especially attractive for the formation of homo- and heterocyclosilanes, as exemplified by the synthesis of sila-, stanna-, and zirconocena-cyclosilanes. A linear bis(potassiumsilyl)acetylene (4a) was used to bridge two zirconocene units, (Cp2Zr(Cl)Si(SiMe3)(2)CCSi(SiMe3)(2)Zr(Cl)Cp-2) (11).