Synthesis of branched polyethylene waxes using benzocycloalkyl pyridine-imine Ni(II) catalysts with dibenzosuberyl group

Our previous works revealed that dibenzosuberyl groups can suppress chain transfer reactions in many late-transition metal-catalyzed ethylene polymerization systems. In this study, we synthesized three benzocycloalkyl or naphthyl pyridine-imine Ni(II) complexes with a single o-aryl dibenzosuberyl substituent. The generated Ni(II) complexes exhibited moderate activities (3.6–7.6 × 105 g·mol−1·h–1) and yielded branched (44–69/1000 C) polyethylene waxes with appropriate molecular weights (3.0–9.1 kg/mol) in ethylene polymerization. Moreover, compared to the planar naphthyl Ni(II) complex, the more stereospecific benzocyclohexyl Ni(II) complex produced 2 times higher molecular weight polyethylene. Most importantly, the single o-aryl dibenzosuberyl substituent can significantly suppress chain transfer during polymerization and increase the molecular weight of the polyethylene produced in this pyridine-imine Ni(II) system with respect to the dibenzhydryl substituent. The resulting branched polyethylene waxes with suitable molecular weights can be used as additives in the plastic processing, coating and dyeing industries.