Stereospecific Styrene Polymerization by Methylalumoxane-Activated Ti (IV) N -Trimethylsilylamido Complexes Bearing the N -Biphenyl or N -(6-(2-(Diethylboryl)phenyl)-Pyrid-2-yl) Motif

摘要

Cp'TiCl_2 (N -(6-(2-(diethylboryl)phenyl)pyrid-2-yl)SiMe_3), [Cp' = C_5H_5 (3), C_5 (CH_3)_5 (4)], and the aminoborane-free half-titanocene analogs with the general formula: Cp'TiCl_2 (N-(biphenyl-3-yl)SiMe_3); [Cp' = C_5H_5 (7), C_5 (CH_3)_5 (8)] are synthesized and used in the polymerization of styrene. All the pre-catalysts are active in styrene polymerization, >90% syndiotactic poly(styrene) (st -PS) is produced, exceeding that of their ansa -homologues (C_5 (CH_3)_5) TiCl_2 (6-(2-(diethylboryl)phenyl)pyrid-2-ylamido)(dimethylsilyl) (9) and (C_5 (CH_3)_5)TiCl_2 (3-biphen-3-ylamido)(dimethylsilyl) (10) both in activity and molecular weight. Pre-catalyst 8 allows for the synthesis of high-molecular-weight st -PS with activities up to 5000 kg_(st-PS) mol_(cat)~(-1) h~(-1). Implications of the 2-(diethylboryl)phenyl)pyrid-2-yl group on polymerization activity and molecular weight are discussed.