Synthesis of Highly Branched Polyethylene Using “Sandwich” (8‑p‑Tolyl naphthyl α‑diimine)nickel(II) Catalysts

Nickel­(II) α-diimine dibromide complexes incorporating 8-p-tolylnaphthylimino groups have been prepared and used for ethylene polymerization by activation with modified methylalumoxane (MMAO). These catalysts possess increased axial bulk relative to standard diimine-nickel complexes, resulting in lower rates of chain transfer relative to chain propagation rates and thus higher polymer molecular weights and narrower PDIs. They yield the most highly branched PE produced by Ni catalysts seen to date. The easy synthesis of 8-aryl-1-naphthylamines provides ready access to a new class of α-diimine-based nickel catalysts in which the 8-substituent is ideally positioned to provide steric bulk at the axial sites.