(<i>η</i>⁵‐Pentamethylcyclopentadienyl)trimethyltitanium as a precursor for the syndiospecific polymerization of styrene

Abstract

Abstract An equimolar mixture of Cp*Ti(CH 3 ) 3 (2) and Ph 3 C + [B(C 6 F 5 ) 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 × 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*TiCl 3 /MAO also function as syndioselective styrene polymerization catalysts, but are less active than the ‘cationic’; system derived from 1 and 2.