Synthesis and reactivity of new mixed dicyclopentadienyl Group 4 metal complexes with the doubly bridged bis(dimethylsilanediyl)-cyclopentadiene-(η5-cyclopentadienyl) ligand

The monocyclopentadienyl titanium complex [Ti{(C5H4)(SiMe2)2(η5-C5H3)} Cl3] 3 and the dichloro mixed dicyclopentadienyl Group 4 metal complexes [M(η5-C5R5){(C5H4)(SiMe2)2(η5-C5H3)} Cl2] (R=H; M=Ti 4, Zr 5, Hf 6; R=Me; M=Ti 7) containing the doubly bridged bis(dimethylsilanediyl)-cyclopentadiene-(η5-cyclopentadienyl) ligand were prepared in high yields by reaction of the monolithium salt Li[(C5H4)(SiMe2)2(C5H3)] 2 with equimolar amounts of TiCl4 or the monocyclopentadienyl complexes [Cp′MCl3], respectively. Reactions of the chloro complexes with various alkylating agents afforded the chloroalkyl [M(η5-C5H5){(C5H4)(SiMe2)2(η5-C5H3)}ClR] (M=Ti; R=Me 8, Et 9; M=Zr, R=Me 10, Et 11, CH2Ph 12; M=Hf, R=CH2Ph 13) and dialkyl [M(η5-C5R5){(C5H4)(SiMe2)2(η5-C5H3)}Me2] (M=Ti; R=H 14, Me 15; M=Zr; R=H 16, compounds. Formation of the heterodinuclear complex [Zr(η5-C5H5)Cl2(η5-C5H3)(SiMe2)2(η5-C5H3)Ti(NMe2)3] 17 with amine elimination was observed by 1H-NMR spectroscopy when complex 5 was reacted with Ti(NMe2)4. The catalytic activity of compounds 3–5 for ethylene polymerization has been studied using MAO as cocatalyst