Investigations of the Ligand Electronic Effects on α-Diimine Nickel(II) Catalyzed Ethylene Polymerization

Lihua Guo; Shengyu Dai; Changle Chen

doi:10.3390/polym8020037

Investigations of the Ligand Electronic Effects on α-Diimine Nickel(II) Catalyzed Ethylene Polymerization

Polymers (Basel). 2016 Jan 29;8(2):37. doi: 10.3390/polym8020037.

Authors

Lihua Guo¹, Shengyu Dai², Changle Chen³

Affiliations

¹ School of Chemistry and Chemical Engineering, Qufu Normal University, Qufu 273165, China. guolihua-qfnu@139.com.
² Key Laboratory of Soft Matter Chemistry, Chinese Academy of Sciences, Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei 230026, China. daiyu@mail.ustc.edu.cn.
³ Key Laboratory of Soft Matter Chemistry, Chinese Academy of Sciences, Department of Polymer Science and Engineering, University of Science and Technology of China, Hefei 230026, China. changle@ustc.edu.cn.

Abstract

The synthesis and characterization of a series of dibenzhydryl-based α-diimine Ni(II) complexes bearing a range of electron-donating or -withdrawing groups are described. Polymerization with ethylene is investigated in detail, involving the activator effect, influence of polymerization conditions on catalyst activity, thermal stability, polymer molecular weight and melting point. All of these Ni(II) complexes show great activity (up to 6 × 10⁶ g of PE (mol of Ni)^-1·h^-1), exceptional thermal stability (stable at up to 100 °C) and generate polyethylene with very high molecular weight (M_n up to 1.6 × 10⁶) and very narrow molecular weight distribution. In the dibromo Ni(II) system, the electronic perturbations exhibit little variation on the ethylene polymerization. In the Ni(acac) system, dramatic ligand electronic effects are observed in terms of catalytic activity and polyethylene molecular weight.

Keywords: Nickel; cocatalyst; dibenzhydryl; electronic effect; ethylene polymerization; α-diimine.