New nickel(II) diimine complexes bearing phenyl and <i>sec</i>‐phenethyl groups: synthesis, characterization and ethylene polymerization behaviour

Abstract

A series of nickel(II) catalysts containing phenyl and chiral sec ‐phenethyl groups, {[(4‐R 1 ‐2‐R 2 C 6 H 2 NC) 2 Nap]NiBr 2 } (Nap: 1,8‐naphthdiyl, R 1 = Me, R 2 = Ph ( 3a ); R 1 = Me, R 2 = sec ‐phenethyl ( 3b ); R 1 = Cl, R 2 = sec ‐phenethyl ( 3c ); R 1 = Me, R 2 = Me ( 3d ) were synthesized and characterized. All organic compounds were fully characterized by FT‐IR and NMR spectroscopy and elemental analysis. The single crystal for X‐ray crystallography was isolated from 3a in CH 2 Cl 2 / n ‐hexane under air; the crystal structure showed a binuclear complex 3a ′, in which each nickel atom was six‐coordinate. The two nickel atoms together with two bromine atoms form a planar four‐membered ring, with a bromine and H 2 O axial ligands. These complexes, activated by diethylaluminum chloride and chiral nickel pre‐catalysts rac ‐ 3c , exhibited good activities (up to 2.85 × 10 6 g PE (mol Ni h bar) −1 ) for ethylene polymerization, and produced polyethylene products with a high degree of branching (up to 117 branched per 1000 carbons) at high temperature. The type and amount of branches of the polyethylenes obtained were determined by 1 H and 13 C NMR spectroscopy. Copyright © 2014 John Wiley &amp; Sons, Ltd.