Switching a Catalyst System from Ethene Polymerization to Ethene Trimerization with a Hemilabile Ancillary Ligand

A drastic ligand effect was observed in the catalytic ethene conversion by the substituted mono(cyclopentadienyl)titaniumtrichloride/methylalumoxane (MAO) catalysts shown. The catalyst with R=Me produces polyethene, whereas the catalyst with R=Ph selectively trimerizes ethene to 1-hexene. This switch in catalyst performance appears to be the result of a hemilabile behavior of the cyclopentadienyl ligand with the pendant arene group, involving reversible coordination of the arene moiety.