Nickel catalyzed synthesis of branched polyethylene waxes using a hybrid steric strategy

Previous work suggests that the mixing of different substituents may have an unexpected effect on transition metal-catalyzed polymerization of ethylene. In this study, we synthesized a series of pyridine-imine Ni(II) complexes bearing o-diarylmethyl and o-aryl substituents. The hybrid steric Ni(II) complexes exhibited moderate activities (0.80-8.5 x 105 5 g center dot mol-- 1 center dot h- 1 ) and yielded branched (54-79/1000 C) polyethylene waxes with appropriate molecular weights (1.8 to 6.8 kg/mol) in ethylene polymerization. Surprisingly, methoxy and bimethoxy nickel catalysts exhibited very low polymerization activity commonality as well as significant different molecular weight polyethylene variability. The complexation of methoxy with diethylaluminum chloride resulting in simultaneous suppression of chain growth and chain transfer may be responsible for the above phenomenon. In addition, high temperature carbon spectra show that these polyethylene waxes are predominantly methyl branched.