Ethylene polymerization 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.