Cyclic organohydroborate complexes of metallocenes: VIII. Triphenylsiloxy derivatives of Group IV organometallic systems, Cp2M(OSiPh3)X (M=Ti, Zr, Hf; X=Cl, {(μ-H)2BC8H14})

Group IV metallocene triphenylsiloxy chlorides, Cp2MCl(OSiPh3) (1, M=Ti; 2, M=Zr; 3, M=Hf), and cyclic organohydroborates, Cp2M(OSiPh3){(μ-H)2BC8H14} (4, M=Zr; 5, M=Hf), were synthesized and characterized. The new hafnocene chloride derivative 3 was obtained by treating Cp2HfCl2 with triphenylsilanol and piperidine. The 18-electron cyclic organohydroborates 4 and 5 were afforded by reacting 2 and 3 with K[H2BC8H14], the potassium salt of the 9-BBN dimer. Reaction of 1 with K[H2BC8H14] causes reduction of the Ti(IV) center and produces the well-known Ti(III), 17-electron, paramagnetic dimer [Cp2Ti(μ-Cl)2TiCp2] (6). Single-crystal X-ray diffraction structures of 3, 4, 5, and 6 were determined.