Synthesis, characterization and ethylene oligomerization behavior of 2-(chloro-substituted-1H-benzoimidazol-2-yl)-6-(1-aryliminoethyl)pyridylnickel dihalides

A series of 2-(chloro-substituted-1H-benzoimidazol-2-yl)-6-(1-aryliminoethyl)pyridines (L1–L6) was synthesized and fully characterized. They reacted with NiCl2 or (DME)NiBr2 to form the corresponding N^N^N tridentate nickel dichlorides (C1–C6) or dibromides (C7–C12). All nickel complexes were characterized by elemental analysis and infrared spectroscopy, while the X-ray diffraction study reveals the distorted octahedral geometry of representative nickel dichloride complex C3 and nickel dibromide complex C7. All nickel complexes, activated with either Et3Al2Cl3 or Et2AlCl, showed good activities in ethylene oligomerization, and notably remarkably high selectivity of α-olefins was achieved in the presence of Et3Al2Cl3. The chloro-substituted ligands enhanced the activities of complexes in ethylene polymerization.

A series of N^N^N tridentate nickel dihalides (C1–C12) ligated by 2-(chloro-substituted-1H-benzoimidazol-2-yl)-6-(1-aryliminoethyl)pyridines were synthesized and characterized. All nickel complexes, activated with either Et3Al2Cl3 or Et2AlCl, showed good activities in ethylene oligomerization, particularly the remarkable high selectivity of α-olefins was achieved in presence of Et3Al2Cl3. The ligands containing chloro-substituents enhanced activities of the corresponding nickel procatalysts in ethylene polymerization.Figure optionsDownload as PowerPoint slideResearch highlights
► The isomers of both ligands and their nickel complexes were carefully investigated.
► The molecular structures of complexes were confirmed by X-ray crystal diffraction.
► The nickel procatalysts provided extensive models in ethylene oligomerization.
► The current nickel procatalysts showed high activities in ethylene oligomerization.
► The chloro-substituted ligands enhanced catalytic activities of the complexes.