Iminopyridyl ligands bearing polyethylene glycol unit for nickel catalyzed ethylene polymerization

Abstract

Influence of polyethylene glycol unit on nickel catalyzed ethylene polymerization have attracted increasing interest. The Lewis basic oxygen atoms on polyethylene glycol group can form interactions with Lewis acidic metal additives. In this contribution, a series of iminopyridyl ligands (L-O1, L-O2 and L-O3) bearing polyethylene glycol units and corresponding nickel complexes (Ni-O1, Ni-O2 and Ni-O3) were designed, synthesized and characterized. By the activation of alkylaluminium cocatalysts, the nickel complexes and their corresponding MgCl2-supported nickel precatalysts (Ni-O1-Mg, Ni-O2-Mg and Ni-O3-Mg) were investigated in catalytic homogeneous and heterogeneous ethylene polymerization, respectively. The molecular weight of products increased with the number of oxygen atoms on polyethylene glycol unit increasing. The introduction of the MgCl2 support resulted in much higher molecular weights and much lower branched densities of polyethylenes than those of products generated in the homogeneous polymerizations. The polymers generated in heterogeneous polymerizations have excellent polymer powder morphology to prevent reactor fouling, facilitating potential industrial applications.