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

Permethylated cyclopentadienyl dinuclear constrained geometry titanium catalyst, [μ-(C6H4)2-2,2′]{(η5-C5Me3)[1-Me2Si(η1-N-tBu)](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(η5-2-PhC5Me3)(η1-N-tBu)TiCl2 (PhTi1) and Me2Si(η5-C5Me4)(η1-N-tBu)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.