Indole-Based Nickel Catalysts for Ethylene Polymerization and Copolymerization with Norbornene Derivatives

In coordination–insertion olefin polymerization, the advancement of high-performance transition-metal catalysts has been a central driving force in both academic and industrial polyolefin research. In this study, a series of single-component indole-based N,O-nickel catalysts were designed. Through systematic modification of the ligand architecture, we achieved precise control over the steric environment of these catalytic systems, which profoundly influenced ethylene (co)polymerization behaviors. Synergistic optimization of catalyst design and polymerization conditions enabled regulation of polyethylene molecular weights, allowing efficient production of polyethylene wax and high-molecular-weight polyethylene (up to 451.3 kg·mol–1). This catalytic system also exhibited exceptional performance in ethylene-norbornene derivative copolymerization, achieving a comonomer incorporation ratio of 36.3 mol %. Notably, the Ni5 catalyst demonstrated significant tolerance toward polar functional groups, enabling the synthesis of ethylene/polar-norbornene copolymers.