Lewis acid modulation in phosphorus phenol nickel catalyzed ethylene polymerization and copolymerization†

Recently, phosphorus phenol nickel catalysts have attracted widespread attention from the academic community due to their excellent copolymerization performance. Here, a series of phosphorus phenol nickel catalysts containing N atoms, which can be coordinated with a metal salt Lewis acid to increase the steric hindrance of catalysts, were designed and synthesized. Based on the coordination of the N atoms of the ligand with different metal salts, we studied ethylene polymerization and copolymerization with polar monomers. Adding metal salts significantly improves the thermal stability of nickel catalysts and the molecular weight of the prepared polyethylene (up to 4.72 × 10⁵ g mol⁻¹, M_n). These catalysts enable copolymerization of ethylene with a series of polar monomers such as methyl acrylate, tert-butyl acrylate, methyl 10-undecenoate and 10-undecenol. More importantly, this metal salt regulation strategy can significantly increase the molecular weight of the copolymer of ethylene and acrylate (up to 3.28 × 10⁴ g mol⁻¹, M_n).