Ethylenepolymerization by 2-iminopyridylnickel halide complexes: synthesis, characterization and catalytic influence of the benzhydryl group

Abstract

A series of 2-(2-benzhydrylbenzenamino)pyridine ligands (L1–L13) was synthesized and used as bidentate N^N ligands with nickel halides to afford the corresponding nickel dihalide complexes L₂Ni₂Cl₄C1–C13 and L₂NiBr₂D1–D13. All ligands and complexes were characterized by IR and NMR spectroscopy, and by elemental analysis. The molecular structures of the representative complexes C1·2CH₃OH, C5·2H₂O, D4, D7 and D9 were confirmed by single-crystal X-ray diffraction studies. Upon activation with either methylaluminoxane (MAO) or ethylaluminium sesquichloride (Et₃Al₂Cl₃, EASC), these nickel pre-catalysts exhibited high activities (up to the range of 10⁷ g mol⁻¹ (Ni) h⁻¹) towards ethylene polymerization, producing branched polyethylenes with narrow polydispersity.