Group IV Mixed Sandwich Compounds:Synthesis of Pentamethylcyclopentadienyl-Titanium, -Zirconium and -Hafnium Cycloheptatrienyl and Cyclooctatetraene Complexes

The first complete series of Group IV sandwich complexes Cp*MCHT (M = Ti, Zr, Hf) (Cp* = η5-C5Me5, CHT = η7-C7H7) has been made and characterized. Cp*HfCHT is the first reported sandwich compound of hafnium. The d1, η8-C8H8(COT) complex Cp*MCOT were also synthesised similarly for M = Ti, Zr, but the complexes with M = Hf was not obtained; the failure to obtain Cp*HfCOT is ascribed to kinetic factors. Cp*ZrCOT is the first thermally-stable paramagnetic organozirconium(III) compound isolated in the solid state. The IR, 1H, 13C NMR, ESR and electronic absorption spectra are discussed