Novel C1 symmetric zirconocenes containing substituted fluorenyl moieties for the polymerization of olefins

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[η5-1-indenyl(1-methylethylidene)-[2,7-bis-(2,4,6-trimethylphenyl)-η5-9-fluorenyl]zirconium (11), dichloro[η5-1-indenyl(1-methylethylidene)-[2,7-bis-(2,6-dimethylphenyl)-η5-9-fluorenyl]zirconium (12), and dichloro[η5-1-indenyl(1-methylethylidene)-[2,7-bis-(2-methylphenyl)-η5-9-fluorenyl] zirconium (13) were highly active for the polymerization of both ethylene and propylene when activated with excess methylaluminoxane (MAO). Dichloro[η5-1-indenyl(1-methylethylidene)-[2,7-dibenzyl-η5-9-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.