Synthesis, characterization and ethylene polymerization behaviour of binuclear nickel halides bearing 4,5,9,10-tetra(arylimino)pyrenylidenes

Abstract

Pyrene-4,5,9,10-tetraone was prepared via the oxidation of pyrene, and reacted with various anilines to afford a series of 4,5,9,10-tetra(arylimino)pyrenylidene derivatives (L1–L4). The tetraimino-pyrene compounds L1 and L2 were reacted with two equivalents of (DME)NiBr₂ in CH₂Cl₂ to afford the corresponding dinickel bromide complexes (Ni1 and Ni2). The organic compounds were fully characterized, whilst the bi-metallic complexes were characterized by FT-IR spectra and elemental analysis. The molecular structures of representative organic and nickel compounds were confirmed by single-crystal X-ray diffraction studies. These nickel complexes exhibited high activities towards ethylene polymerization in the presence of either MAO or Me₂AlCl, maintaining a high activity over a prolonged period (longer than previously reported dinickel complex pre-catalysts). The polyethylene obtained was characterized by GPC, DSC and FT-IR spectroscopy and was found to possess branched features.