Homogeneous and Heterogeneous α-Diimine Ni(II) Catalysts with Asymmetric Fluorine-Containing Diphenylmethyl Substituents for the Polymerization of Ethylene.

To improve the thermal stabilities and polymerization activities of α-diimine nickel catalysts, two asymmetric nickel complexes, Cat1 and Cat2, bearing large steric hindrance fluorine-containing diphenylmethyl substituents were designed, synthesized and used for ethylene polymerization. These two homogeneous catalysts exhibited good thermal stability, especially Cat2, which exhibited an activity of 2.04 × 106 gPE/molNi h at 80 °C. To control the polymer particle morphology and avoid the fouled reactor, these α-diimine catalysts were covalently bonded to modified silica supports, and two supported α-diimine catalysts, S-Cat1 and S-Cat2, were prepared for ethylene polymerization. The particle morphology of the polyethylene was substantially improved. Additionally, the melting point of the polyethylene was increased to approximately 110–120 °C. The molecular weight of the polymer prepared with the supported catalyst was nearly twice that of the polymer catalyzed by the corresponding homogeneous catalyst, and the molecular weight of the polyethylene prepared by S-Cat2 reached 1790 kg/mol. The substituents on the ligands affected the properties of the α-diimine nickel catalysts and the microstructure of the resulting polyethylene. [ABSTRACT FROM AUTHOR]