(ETA-5-PENTAMETHYLCYCLOPENTADIENYL)TRIMETHYL-TITANIUM AS A FOR THE SYNDIOSPECIFIC POLYMERIZATION OF STYRENE

An equimolar mixture of Cp*Ti(CH3)3 (2) and Ph3C+[B(C6F5)4] (1) forms a highly active and syndioselective catalyst for the polymerization of styrene, producing 96% syndiotactic polystyrene (PS) at an activity of 0.91 x 10(7) g PS(mol Ti)-1 (mol styrene)-1 h-1. Both activity and syndioselectivity can be increased using tri-isobutylaluminum (TIBA) to scavenge the system. ESR measurements indicate that the polymerization proceeds via titanium(IV) intermediates. Catalysts derived from 2/methylaluminoxane (MAO) as well as Cp*TiCl3/MAO also function as syndioselective styrene polymerization catalysts, but are less active than the 'cationic' system derived from 1 and 2.