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.