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

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‐C 6 H 4 )C 6 H 3 N=C) 2 Naphth]NiBr 2 , 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‐Et 2 AlCl systems via controlled chain‐walking ethylene polymerization performed with high catalytic activities of up to 3.10 × 10 6 g PE (mol Ni h) −1 to yield high molecular weight branched PEs with narrow M w / M n values (PDI ≤ 2.39). This Ni (II) system also conducted the chain‐walking polymerization of 1‐octene, resulting in highly branched polyolefins (up to 10 7 branches/1000C).