SYNTHESIS AND CRYSTAL-STRUCTURE OF THE TRIS(AMIDE) CATIONS [M(N(SIME3)(2))(3)](- EVIDENCE FOR M-SI-C INTERACTIONS() (M = ZR OR HF) )

Reaction of the strong Lewis acid B(C6F5)(3) with [M{N(SiMe3)(2)}(3)Me ] (M = Zr or Hf) gave the compounds [M{N(SiMe3)(2)}(3)][MeB(C6F5)(3)]. Crystallographic analyses of these compounds revealed the formation o f multicentre bonds between the SiCH3 units of the amide ligands and t he otherwise electron-deficient metal centre. The new tris(amide) comp lexes [M{N(Ph)SiMe3}(3)Cl] and [M{N(Ph)SiMe3}(3)Me] (M = Zr or Hf) hav e also been synthesized.