Chain‐walking polymerization of ethylene and 1‐octene with ortho‐phenyl‐based α‐diimine Ni (II) catalysts

Abstract

A class of ortho‐phenyl‐substituted Ni (II) α‐diimine complexes with variable electronic nature in the 4‐phenyl position, {[(4‐Me‐2‐(4‐R‐C6H4)C6H3N=C)2Naphth]NiBr2, R = OMe (C1); R = Me (C2); R = H (C3)}, was prepared and characterized. These nickel dibromide complexes were confirmed by X‐ray crystallography analysis and crystallized as a centrosymmetric bromine‐bridged dimer in a distorted tetrahedral geometry at the two Ni (II) centers connected by a four‐membered ring. Because of the conjugation effect and steric hindrance effect of ortho‐phenyl substituent, these Ni‐Et2AlCl systems via controlled chain‐walking ethylene polymerization performed with high catalytic activities of up to 3.10 × 106 g PE (mol Ni h)−1 to yield high molecular weight branched PEs with narrow Mw/Mn values (PDI ≤ 2.39). This Ni (II) system also conducted the chain‐walking polymerization of 1‐octene, resulting in highly branched polyolefins (up to 107 branches/1000C).