New nickel(II) diimine complexes bearing phenyl and sec‐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 N¼C) 2 Nap]NiBr 2 } (Nap: 1,8naphthdiyl, 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) À1 ) 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. . a, 1b, 1c, 2d and 3d are known compounds and characterization data can be seen in the supporting information.New nickel(II) diimine complexes for ethylene polymerization

Synthesis of Highly Branched Polyolefins Using Phenyl Substituted α-Diimine Ni(II) Catalysts

“…Et 2 AlCl and MMAO were donated by Tosoh-Finechem. Pd(II) catalyst [ 30 ], 4 [ 30 ], 5 [ 30 ], L4 [ 27 ], L5 [ 29 ], L6 [ 31 ], C4 [ 27 ], C5 [ 29 ] and C7 [ 32 ] were prepared according to the literature procedures. Other chemicals were commercially obtained and purified with common procedures.…”

“…Recently, we reported that bulky chiral ortho-sec- diphenethyl-substituted [ 25 , 26 ] and ortho- phenyl substituted [ 27 , 28 , 29 ] α-diimine Ni(II) and Pd(II) complexes that exhibited high activities towards ethylene polymerization and produced highly-branched polyethylene upon activation with Et 2 AlCl. In this context, we have become very interested in phenyl-substituted α-diimine ligand Ni(II) precursors for polymerization of ethylene and 1-alkenes at the different conditions.…”

Precision Chain‐Walking Polymerization of trans‐4‐Octene Catalyzed by α‐Diimine Nickel(II) Catalysts Bearing ortho‐sec‐Phenethyl Groups

“…We have previously reported that bulky ortho‐sec‐ phenethyl ‐ substituted and ortho‐ phenyl substituted α‐ diimine nickel and palladium complexes exhibited high activities toward ethylene polymerization and produced highly branched polyethylene upon activation with Et 2 AlCl or MMAO, and also produced branched poly(1‐alkene)s with high molecular weight. We anticipated that bulky α‐ diimine ligands might control chain walking and produce regioregular polymers.…”

Cationic para‐phenyl‐substituted α‐diimine nickel catalyzed ethylene and 4‐methyl‐1‐pentene (co)polymerizations via living/controlled chain‐walking

“…Our group showed recently that fast chain‐walking process in α‐ diimine based nickel system can be efficiently modulated via the introduction of phenyl substituents . Consequently, these phenyl‐substituted complexes catalyzed ethylene, linear 1 ‐, 2 ‐ olefin and 4 ‐ octene polymerizations to afford high molecular weight polymers with different branching structures and demonstrated living behavior at low temperature. In this work, we report the polymerization of 4MP using a series of phenyl‐substituted α‐ diimine nickel catalysts in combination with Et 2 AlCl, and investigated the effects of catalyst structure and polymerization temperature on branching degree and insertion pathways.…”