Abstract
The asymmetric ansa-ligand precursors Me2Si(C5Me4H)(C5H4R) [R = CH2CH2PPh2 (1), PPh2 (2)] and their lithium derivatives Li2{Me2Si(C5Me4)(C5H3R)} [R = CH2CH2PPh2 (3), PPh2 (4)] have been prepared. The group 4 metal ansa complexes [M{Me2Si(η5-C5Me4)(η5-C5H3R)}Cl2] [M = Ti, R = CH2CH2PPh2 (5), PPh2 (6); M = Zr, R = CH2CH2PPh2 (7), PPh2 (8); M = Hf, R = CH2CH2PPh2 (9), PPh2 (10)] were obtained by the reaction of [TiCl4(THF)2] or MCl4 (M = Zr or Hf) and the corresponding lithiated ansa derivative. The reaction of complexes 7 and 8 with two equivalents of MgMeCl led to the formation of the alkyl complexes [Zr{Me2Si(η5-C5Me4)(η5-C5H3R)}Me2] [R = CH2CH2PPh2 (11), PPh2 (12)]. Methyl abstraction from 11 and 12 with B(C5F6)3 gave the cationic species [Zr{Me2Si(η5-C5Me4)(η5-C5H3R)}Me]+ [R = CH2CH2PPh2 (13), PPh2 (14)]. The insertion reaction of the isocyanide reagent CNC6H3Me2-2,6 into the Zr−Me bond of complex 12 giving the corresponding η2-iminoacyl compound [Zr{Me2Si(η5-C5Me4)(η5-C5H3PPh2)}{η2-MeC=N(C6H3Me2-2,6)}(Me)] (15) is described. The ansa-niobocene imide [Nb(=NtBu){Me2Si(η5-C5Me4)(η5-C5H3PPh2)}Cl] (16) and the niobocene imide complexes [Nb(=NtBu)(η5-C5H4PPh2)2Cl] (17) were synthesised by the reaction of [Nb(=NtBu)Cl3(py)2] with Li2{Me2Si(C5Me4)(C5H3PPh2)} (4) or two equivalents of Li(C5H4PPh2), respectively. Preliminary results for the catalytic activity of 7 and 8 in the polymerization of ethylene are presented. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)
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