8-Sila-4-stanna-s-tetrahydroindacenes as synthons for Me2Si-bridged zirconocenes: formation from biscyclopentadienyl silanes by reaction with aminostannanes

Alkyl-substituted bis(cyclopentadienyl)dimethylsilanes react with Me2Sn(NEt2)2 and with (Me2N)4Sn to yield correspondingly substituted, meso-configurated RS-8-sila-4-stanna-s-tetrahydroindacene and axially symmetric RR,SS-4-spiro-bis(8-sila-4-stanna-s-tetrahydroindacene) compounds, respectively, which are stereoselectively converted by reaction with ZrCl4 to the corresponding meso- and rac-configurated ansa-zirconocene complexes.