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

A series of 2-(2-benzhydrylbenzenamino) pyridine ligands (L1-L13) was synthesized and used as bidentate N boolean AND N ligands with nickel halides to afford the corresponding nickel dihalide complexes L2Ni2Cl4 C1-C13 and L2NiBr2 D1-D13. All ligands and complexes were characterized by IR and NMR spectroscopy, and by elemental analysis. The molecular structures of the representative complexes C1 center dot 2CH(3)OH, C5 center dot 2H(2)O, 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 10(7) g mol(-1) (Ni) h(-1)) towards ethylene polymerization, producing branched polyethylenes with narrow polydispersity.