Ethylene and ethylene/1-hexene (co)polymerizations with 2,5-dimethylcyclopentadienyl ansa-titanocene and zirconocene complexes

Cl-bridged 2,5-dimethylcylcopentadienyl ansa-titanocene complexes, [Me(H)C(eta(5)-C5H4)(eta(5)-2,5-Me2C5H2)]TiCl2 (4) and [(CH3CH2CH2)(H)C(eta(5)-C5H4)(eta(5)-2,5-Me2C5H2)]TiCl2 (5) and a dinuclear titanium complex, Me2Si[(eta(5)-2,5-Me2C5H2)Ti{O(2,6-iPr(2)C(6)H(3))} Cl-2] (7) have been prepared. The solid state structure of 4 has been determined by X-ray crystallography. Ethylene polymerization reactivities of 4, 5, 7 and the structurally related ansa-zirconocene complexes, [Me(H)C(eta(5)-C5H4)(eta(5)-2,5-Me2C5H2)]ZrCl2 (1), [(Me)(H)C(eta(5)-2,5-Me2C5H2)(2)]ZrCl2 (2) and [Me2Si(eta(5)-2,5-Me2C5H2)(2)]ZrCl2 (3) are investigated after activation with MAO. Interestingly, the ansa-titanocene complexes 4 and 5 show much higher activity than the ansa-zirconocene complexes 1 and 2, and the molecular weights of the polymers obtained by the titanocene complexes are significantly higher (M-w, similar to 800 000) than those of polymers obtained by the zirconocene complexes (M-w, below 200 000). The Me2Si-bridged complex 3 shows extremely high activity for ethylene polymerization and the activity (290 x 10(6) g/mol h) is 15 times higher than that of [Me2Si(Me4C5)(NtBu)]TiCl2 (CGC) under the same conditions. Ethylene/1-hexene copolymerization reactivities of 3 and 5 have been studied. The complexes are inferior to CGC in terms of comonomer incorporation ability. (c) 2005 Elsevier Ltd. All rights reserved.