Niobium, titanium, zirconium and hafnium complexes incorporating germanium bridged ansa ligands. X-Ray crystal structures of [Zr{Me2Ge(η5-C5Me4)2}Cl2] and [M{Me2Ge(η5-C5Me4)(η5-C5H4)}Cl2] (M=Zr, Hf)

Both the symmetric and asymmetric ansa-ligand precursors Me2Ge(C5Me4H)2 (1) and Me2Ge(C5Me4H)(C5H4R) (R=H (3), Me (4)) and their lithium derivatives Li2{Me2Ge(C5Me4)2} (5) and Li2{Me2Ge(C5Me4)(C5H3R)} (R=H (6), Me (7)) have been prepared. The ansa-niobocene imido complex [Nb(NBut){Me2Ge(η5-C5Me4)(η5-C5H4)}Cl] (8) was synthesized by the reaction of [Nb(NBut)Cl3(py)2] with the appropriate lithiated ansa-precursor. The Group 4 metal complexes containing germanium bridged ansa-ligands [M{Me2Ge(η5-C5Me4)2}Cl2] (M=Ti (9), Zr (10), Hf (11)), [M{Me2Ge(η5-C5Me4)(η5-C5H4)}Cl2] (M=Ti (12), Zr (13), Hf (14)), and [M{Me2Ge(η5-C5Me4)(η5-C5H3Me)}Cl2] (M=Ti (15), Zr (16), Hf (17)) were prepared by the reaction of MCl4 and the corresponding lithiated ansa-derivative. The molecular structures of 10, 13 and 14 were determined by single-crystal X-ray diffraction studies. Preliminary results for the catalytic activity of the Group 4 ansa-metallocene complexes in the polymerization of ethylene and propylene are reported.