Effect of Cyclopentadienyl and Anionic Ancillary Ligand in Syndiospecific Styrene Polymerization Catalyzed by Nonbridged Half-Titanocenes Containing Aryloxo,Amide,and Anilide Ligands:Cocatalyst Systems

摘要

Styrene polymerizations with a series of nonbridged half-titanocenes of the type CpTiCl_2(L) [L=2,6-~iPr_2C_6H_3,Cp'=Cp (1),l,3-Me_2C_5H_3 (2),l,2,4-Me_3C_5H_2 (3),C_5Me_5 (Cp~*,4);Cp'=Cp~*,L= OPh (5),O-4-MeC_6H_4 (6),0-2,6-Me_2C_6H_3 (7),O-2,6-~tBu_2C_6H_3 (8);Cp'= l,3-Me_2C_5H_3,L - NMeCy (9,Cy =cyclohexyl),N(2,6-Me_2C_6H_3)(SiMe_3) (10);L=Cl,Cp'=Cp (I'),l,3-Me_2C_5H_3 (2'),l,2,4-Me_3C_5H_2 (30,C_5Me_5 (Cp~*,40] have been explored in the presence of MAO cocatalyst under various conditions.The catalytic activities for syndiospecific styrene polymerization with a series of half-titanocenes containing an aryloxo ligand,Cp'TiCl_2(O-2,6-~iPr_2C_6H_3),were higher than those with the trichloro analogues,Cp'TiCl_3,and the activity with a series of Cp~* analogues (4,4',5-8) and l,3-Me_2C_5H_3 analogues (2,2',9,10) were highly dependent upon the anionic donor ligand used.(~tBuC_5H_4)TiCl_2(O-2,6-~iPr_2C_6H_3) (11) exhibited a relatively high catalytic activity for syndiospecific styrene polymerization at 25 deg C when both [PhMe_2NH]B(C_6F_5)_4 and a mixture of Al~iBu_3/Al(n-C_8H_(17))_3 were used as the cocatalyst,and the activity with a series of (l,3-Me_2C_5H_3)TiCl_2(OAr) depended on the aryloxide ligand used.The role of the anionic donor ligand,like the aryloxide ligand,toward both the catalytic activity and the M_w values of polystyrene has thus been observed irrespective of the kind of cocatalyst employed.