A biphenylene-bridged dinuclear constrained geometry titanium complex for ethylene and ethylene/1-octene polymerizations

Abstract

Permethylated cyclopentadienyl dinuclear constrained geometry titanium catalyst, [mu-(C6H4)(2)-2,2']{(eta(5)-C5Me3)[1-Me2Si(eta(1)-N-Bu-t)](TiCl2)}(2) (BPTi2) linked by a biphenylene bridge was synthesized and tested in ethylene and ethylene/1-octene polymerizations upon activation by TIBA (triisobutylaluminum)/[Ph3C][B(C6F5)(4)]. When compared with the corresponding highly active, mononuclear analogs, Me2Si(eta(5)-2-PhC5Me3)(eta(1)-N-Bu-t)TiCl2 (PhTi1) and Me2Si(eta(5)-C5Me4)(eta(1)-N-Bu-t)TiCl2 (MeTi1), BPTi2 exhibits significantly increased molecular weight of polymer (>two-fold), as well as high level of activity and 1-octene incorporations in ethylene and ethylene/1-octene polymerizations. Although the lower activity was observed at high 1-octene feeds, the combined effects of rigidity and electronic conjugation induced by the biphenylene bridge might be responsible for the observed polymerization properties of BPTi2. (C) 2011 Elsevier B.V. All rights reserved.