Symmetric and Asymmetric Binuclear α-Diimine Nickel(II) Complexes for Ethylene Polymerization

A series of symmetric and asymmetric binuclear α-diimine nickel(II) complexes toward ethylene polymerization were successfully synthesized and characterized by 1HNMR. All the catalysts were typically activated with MAO and displayed good activity at room temperature under 1atm ethylene pressure. The symmetric catalyst containing isopropyl on ligand activated with 500 equiv MAO produced high molecular weight polyethylene with a PDI=1.75, while the symmetric catalyst containing methyl on ligand produced relatively low molecular weight polyethylene with a PDI=1.74. By contrast, the molecular weight, branching density of resultant polymer produced by asymmetric catalyst decrease roughly somewhere between that of polymers prepared by two symmetric catalysts.