Ethylene and hydrogen effects in propylene polymerization with 2-arylindenyl zirconocenes

Addition of small amounts of ethylene or hydrogen leads to significant prod uctivity increase in propylene polymerization catalyzed by fluxional bis(2- arylindenyl)zirconocenes. To test if this phenomenon is related to the reac tivation of dormant species formed as a result of regioirregular propylene insertions, we have reinvestigated the regioregularity of these catalysts. Approximately 0.1-0.3 mol% of 2,1-misinsertions were found in polymers synt hesized by these catalysts. The presence of these regioirregular insertions could account for the ethylene and hydrogen effects observed but does not rule out formation of other catalyst dormant sites. (C) 2000 Elsevier Scien ce B.V. All rights reserved.