N-(Pyridin-2-yl)picolinamide tetranickel clusters: Synthesis, structure and ethylene oligomerization

A series of N-(pyridin-2-yl)picolinamide derivatives was synthesized and characterized. Tetranickel complexes were obtained by stoichiometric reaction of NiBr2 and corresponding ligands, and characterized by elemental and spectroscopic analysis. Moreover, the coordination pattern of complex 3a was confirmed by single-crystal X-ray diffraction. In the structure, two ligands linked two nickel atoms to form a unit, and two units were bridged via μ3-OMe and μ2-Br to form a tetranickel cluster. These Ni(II) complexes were investigated in ethylene oligomerization and found to exhibit remarkable catalytic activities upon activation with MAO. Reaction conditions as well as ligand environment significantly affected the catalytic performance of the nickel complexes; the highest activity could be achieved to be 2.7 × 106 g mol−1 Ni h−1.

Graphical abstractNickel complexes of N-(pyridin-2-yl)picolinamide derivatives were synthesized and characterized. X-ray crystallographic analyses revealed that complex 3a as a tetranickel cluster has four nickel atoms coordinated with four bridging ligands via μ3-OMe and μ2-Br bridges. These complexes exhibited good activities in ethylene oligomerization with C4 as the main product.Figure optionsDownload full-size imageDownload as PowerPoint slide