| 摘要 |
Metallocene catalysts useful for the preparation of syndiotactic/atactic block polyolefins have the general formula R''(C4R'mC5C4R'n) XMeQ wherein X is an hetero-atom ligand with one or two lone pair electrons selected from the elements of Group VA or VIA which can be substituted or non-substituted; (C4Rm'C5C4Rn') is a fluorenyl or a symmetrically substituted fluorenyl or cyclopentadienyl ring; R' is hydrogen or hydrocarbyl radical having from 1-20 carbon atoms, a halogen, an alkoxy, and alkoxy alkyl or an alkylamino or alkylsilylo radical, each R' may be the same or different and m and n independently are 0, 1, 2, 3 or 4, with the proviso that the bilateraly symmetry is maintained; R'' is a structural bridge between X and the (C4R'mC5C4R'n) ring to impart stereorigidity; Q is a hydrocarbyl radical having 1-20 carbon atoms or is a halogen; Me is a Group IIIB, IVB, VB, or VIB metal as positioned in the Periodic Table of Elements; and Me can be in any of its theoretically possible oxidation states. Olefin monomers (particularly propylene) polymerised using those catalysts to form syndiotactic/atactic block polymers of high molecular weight and comprising at least 70% of syndiotactic triads.
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