In Situ Generated Heterometallic Nickel–Zinc Catalysts for Ethylene Polymerization

We have prepared a new series of organometallic nickel complexes ligated by 1-picolyl-4-carboxamidate-1,2,3-triazole donors. Solution metal binding studies by NMR spectroscopy indicated that their reactions with zinc chloride led to the formation of nickel–zinc heterometallics with undefined compositions. These nickel–zinc complexes showed increasing ethylene polymerization activity over the course of 3 h and provided polymers with multimodal distributions. In comparison, the mononickel complexes exhibited constant activity over time and gave narrowly dispersed low molecular weight polyethylene (Mn = ∼103). The addition of zinc sources other than ZnCl2 or other metal salts to the mononickel catalysts did not lead to enhancements in their catalytic performance. Our results suggest that further modifications of the carboxamidatetriazole platform are needed to obtain well-defined heterobimetallic complexes for the controlled synthesis of ethylene-based polymers.