(η5‐Pentamethylcyclopentadienyl)trimethyltitanium as a precursor 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 × 107 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.