New half-metallocene catalysts generating polyethylene with bimodal molecular weight distribution and syndiotactic polystyrene

Abstract

A new type of half-metallocene catalyst for the polymerization of ethylene and styrene, Cp*M((O)3O9Si7 (c-C5H9)7) (M = Ti (1); Zr (2)), is prepared by the reaction of (HO)3O9Si7 (c-C5H9)7 with Cp*MCl3 in the presence of triethylamine. Complex 1 is stable to heat and air, but its heavier congener 2 is slightly air-sensitive. The catalytic systems 1/MMAO and 2/ MMAO, in which MMAO is modified methyl methylaluminoxane, show good activities in ethylene polymerization, with that of 2/MMAO greater than that of 1/MMAO. Polyethylenes with bimodal molecular weight distributions were obtained. In addition, the catalytic system 1/MMAO shows fairly good activities for the syndiospecific polymerization of styrene.