-Chlorinated α‑Diimine Nickel Precatalysts Resulting Polyethylenes with Improved Mechanical Properties and Controlled Crystallinity.

A series of -chlorinated -(6-benzhydryl-2,4-dichlorophenylimino)-'-aryliminoacenaphthylene derivatives as ligands (-, aryl = 2,6-dimethylphenyl (), 2,6-diethylphenyl (), 2,6-diisopropylphenyl (), 2,4,6-trimethylphenyl (), 2,6-diethyl-4-methylphenyl (), 6-benzhydryl-2,4-dichlorophenyl ()) were successfully synthesized and used for their corresponding nickel complexes (-). All organic compounds were comprehensively characterized using NMR, FT-IR, and EA techniques; the nickel complexes had their components determined through FT-IR and EA analysis, and the unambiguous molecular structures of representative nickel complexes were confirmed via single-crystal X-ray diffraction, revealing that and possessed a distorted octahedral geometry around the nickel center. Upon activation with EASC, all nickel complexes demonstrated high catalytic activity (4.7 to 37.9 × 10 g mol h) for ethylene polymerization, with achieving peak performance (12.2 × 10 g mol h) at 50 °C in 30 min. Impressively, the catalytic system demonstrated exceptional thermal stability, maintaining high activity above 9 × 10 g mol h across a broad temperature range (40-70 °C) with minimal fluctuations. Contrary to typical chain-walking behavior observed in α-diimine nickel catalysts, the resultant polyethylene exhibited high crystallinity and minimal long-chain branching despite narrow polydispersity (Đ = 1.8-2.9) and moderate molecular weights (tens of thousands). Systematic modulation of ligand structure and polymerization conditions enabled precise control over crystallinity ( : 6.4 to 62.6%), which was directly correlated with tunable mechanical properties (σ: 1.9-13.1 MPa, ε: 178.8-1030.6%). Representative samples of the resultant polyethylene displayed exceptional tensile strength (13.1 MPa), high elongation at break (1030.6%), and notable elastic recovery (65%), suggesting new types of thermoplastic elastomers.