摘要:
The synthesis and polymerization behavior of four new asymmetric ansa-metallocenes containing a 2,7-disubstituted fluorenyl moiety and an indenyl moiety is reported. Three of the four catalysts, dichloro[eta(5)-1-indenyl(1-methylethylidene)-[2,7-bis-(2,4,6-trimethylphenyl)-eta(5)-9-fluorenyl]zirconium (11), dichloro[eta(5)-1-indenyl(I-methylethylidene)-[2,7-bis-(2,6-dimethylphenyl)-eta(5)-9-fluorenyl]zirconium (12), and dichloro[eta(5)-1-indenyl(l-methylethylidene)-[2,7-bis-(2-methylphenyl)-eta(5)-9-fluorenyl] zirconium (13) were highly active for the polymerization of both ethylene and propylene when activated with excess methylaluminoxane (MAO). Dichloro[eta(5)-1-indenyl(1-methylethylidene)-[2,7-dibenzyl-eta(5)-9-fluorenyl]zirconium (14) was poorly active for the polymerization of ethylene and was therefore not evaluated as a propylene catalyst. The activities for propylene polymerizations with catalysts 11 - 13 increased as the size of the substituents around the ligand framework increased, following the trend 11 > 12 > 13. Molecular weights of the polypropylenes decreased as the temperature was increased. The molecular weight data follows the same trend (11 > 12 > 13) as the activity data, wherein the largest substituents gave rise to the highest molecular weights. (C) 2003 Elsevier Science B.V. All rights reserved.