Synergistic effects of methoxy and Benzhydryl substituents in α-Diimine nickel catalysts for Homo- and copolymerization of 1-Hexene and norbornene

A series of unsymmetrical α-diimine nickel(II) catalysts bearing ortho-bulky dibenzhydryl and electron-donating N-aryl substituents were synthesized, fully characterized, and applied in the homo- and copolymerization of 1-hexene and norbornene. These catalysts exhibited high catalytic activity and remarkable polymerization efficiency upon activation with MAO and B(C₆F₅)₃. In the homopolymerization of 1-hexene, the catalysts demonstrated turnover frequencies up to 78 h⁻¹, yielding highly branched, high-molecular-weight poly(1-hexene) (M_n: 182 kg mol⁻¹). For norbornene polymerization, the highest catalytic activity of 2.61 × 10⁴ g mol⁻¹h⁻¹ and molecular weight of 274 kg mol⁻¹ were achieved. The copolymerization of norbornene and 1-hexene yielded copolymers with tunable 1-hexene incorporation (27.8–33.4 mol%) and high molecular weights (up to 106 kg mol⁻¹), displaying excellent thermal stability (>400 °C). These findings highlight the synergistic effects of steric bulk and electronic modifications in enhancing catalytic performance and polymer properties.