Influence of ortho ‐Electron‐Donating Units on Phosphino‐Phenolate Nickel‐Catalyzed Ethylene (Co)polymerization

ABSTRACT The impact of electron‐donating groups (EDGs) at the ortho‐ phenoxy position of phosphino‐phenolate nickel catalysts on ethylene polymerization and copolymerization with polar monomers was systematically investigated. Three phosphino‐phenolate catalysts based on EDG ( Ni1 , –OMe; Ni2 , –OH; Ni3 , –CH 2 OH) were designed and synthesized, which are moderately active single‐component catalysts for ethylene polymerization at elevated temperatures (up to 150°C), producing high molecular weight linear polyethylene with a melting point as high as 136.0°C. The reduced electron‐donating ability of EDG decreased the activity and molecular weight. Most importantly, a single crystal of the Ni–Li heterobimetallic complex, based on Ni1 and a lithium Lewis acid unit, was confirmed by X‐ray diffraction analysis. Besides, Ni1 and Ni2 demonstrated superior performance in ethylene/polar monomers copolymerization, achieving 1.9‐mol% polar monomer incorporation, resulting in excellent surface properties of the copolymer. The impact of ortho ‐phenoxy EDGs in phosphino‐phenolate nickel catalysts is explored, revealing their high thermal stability and activity in ethylene polymerization to yield high molecular weight linear polyethylene. Notably, these catalysts exhibit excellent performance in ethylene copolymerization with polar monomers, significantly enhancing copolymer surface properties.