The asymmetric ansa-ligand precursors (C5Me4H)SiMe2(C5H4R) (R = H (1), Me (2), SiMe3 (3), i Pr (4)) and their lithium derivatives [Me2Si(C5Me4)(C5H3R)]Li2 (R = H (5), Me (6), SiMe3 (7), i Pr (8)) have been prepared. The ansa-niobocene imido complexes [Me2Si(η5-C5Me4)(η5-C5H3R)]Nb(N t Bu)Cl (R = H (9), Me (10), SiMe3 (11), i Pr (12)) were synthesized by the reaction of Nb(N t Bu)Cl3(py)2 with [Me2Si(C5Me4)(C5H3R)]Li2 in THF. The ansa-zirconocene complexes [Me2Si(η5-C5Me4)(η5-C5H3R)]ZrCl2 (R = H (13), Me (14), SiMe3 (15), i Pr (16)) were prepared by the reaction of ZrCl4 and the corresponding lithiated ansa-derivative. The molecular structures of 10, 12, 13, and 14 were determined by single-crystal X-ray diffraction studies. Preliminary results for the catalytic activity of 13−16 in the polymerization of ethylene are reported.

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The asymmetric ansa-ligand precursors Me 2 Si(C 5 Me 4 H)(C 5 H 4 R) [R = CH 2 CH 2 PPh 2 (1), PPh 2 (2)] and their lithium derivatives Li 2 {Me 2 Si(C 5 Me 4 )(C 5 H 3 R)} [R = CH 2 CH 2 PPh 2 (3), PPh 2 (4)] have been prepared. The group 4 metal ansa complexes [M{Me 2 Si(η 5 -C 5 Me 4 )(η 5 -C 5 H 3 R)}Cl 2 ] [M = Ti, R = CH 2 CH 2 PPh 2 (5), PPh 2 (6); M = Zr, R = CH 2 CH 2 PPh 2 (7), PPh 2 (8); M = Hf, R = CH 2 CH 2 PPh 2 (9), PPh 2 (10)] were obtained by the reaction of [TiCl 4 (THF) 2 ] or MCl 4 (M = Zr or Hf) and the corresponding lithiated ansa derivative.