Ethylene polymerization with an alpha-diimine nickel (II) complex covalently supported on SiO2

Abstract

Abstract A new strategy has been developed to prepare silica-supported α- diimine nickel (II) complex for ethylene polymerization. The bis(4-allyl-2,6- diisopropylphenyl-imino)acenaphthene was modified by the introduction of reactive Si-Cl end groups, allowing the immobilization of them via the direct reaction of the Si-Cl groups with hydroxyls on the silica surface. The resultant Si-Cl-modified bis(4-allyl-2,6-diisopropylphenyl-imino)acenaphthene ligand and the SiO2 supported ligand were characterized by NMR and FTIR spectroscopic techniques, respectively. The reaction of the supported ligand with (1,2-dimethoxyethane)NiBr2 ((DME)NiBr2) gives rise to silica-supported Ni(II) precatalyst, which exhibits high catalytic activities for ethylene polymerization in the presence of inexpensive general alkylaluminum compounds. According to high-temperature GPC, the polyethylene had average molecular weights in the range 0.246x106---1.217x106 and molecular weight distributions in the range 3.17-3.51. The resultant polyethylenes were confirmed by 13C-NMR to contain significant amounts not only of methyl but also of ethyl, propyl, butyl, amyl, and longer side chains (longer than six carbons).