Synthesis and Structures of Titanium and Zirconium Trisiloxides

The synthesis and structures of zirconium and titanium trisiloxides containing the tridentate ligand [MeSi(RMeSiO)3]3- (rac-l,l-3)-3H (R = Si(SiMe3)2Me) are reported. Reactions of rac-l,l-3 with M(OEt)4, where M = Ti or Zr, gave tridentate complexes of formula [MeSi(RMeSiO)3]MOEt (l,l-4, M = Ti; l,l-5, M = Zr). In striking contrast, treatment of rac-l,l-3 with Zr(NEt)4 afforded the spirocyclic complex {[MeSi(RMeSiO)3]2Zr}H2 (l,l-7). These compounds feature bicyclooctane structures, which are hitherto unknown in the chemistry of metal siloxides.