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) alpha-diimine complexes with variable electronic nature in the 4-phenyl position, {[(4-Me-2-(4-R-C6H4)C6H3N=C)(2)Naphth]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 x 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).