A series of dibenzhydryl-based iminopyridine-N-oxide ligands bearing a range of electron-donating or-withdrawing substituents(OMe,H;and NO_(2))and corresponding nickel pre-catalysts are prepared and characterized.The ...A series of dibenzhydryl-based iminopyridine-N-oxide ligands bearing a range of electron-donating or-withdrawing substituents(OMe,H;and NO_(2))and corresponding nickel pre-catalysts are prepared and characterized.The substituents are installed at different positions on the ligand structure,including 4-position of the pyridine-N-oxide moiety(position X)and 4-position of the aniline moiety(position Y).These nickel pre-catalysts are highly active in ethylene polymerization with the addition of very little amount of aluminum cocatalysts,leading to the formation of polyethylenes with molecular weights of well above one million.Electron-donating substituents make the catalysts sensitive to polymerization temperature.In contrast,the catalysts bearing electron-withdrawing NO_(2) substituents show relatively steady performances at different temperatures.Most importantly,we demonstrate that different substituents and different positions both play important roles in determining the properties of nickel catalysts.This provides an alternative strategy for the future design of high-performance polymerization catalyst.展开更多
基金the National Natural Science Foundation of China(Grant Nos.52025031,21690071,22001004,U19B6001 and U1904212)K.C.Wong Education Foundation。
文摘A series of dibenzhydryl-based iminopyridine-N-oxide ligands bearing a range of electron-donating or-withdrawing substituents(OMe,H;and NO_(2))and corresponding nickel pre-catalysts are prepared and characterized.The substituents are installed at different positions on the ligand structure,including 4-position of the pyridine-N-oxide moiety(position X)and 4-position of the aniline moiety(position Y).These nickel pre-catalysts are highly active in ethylene polymerization with the addition of very little amount of aluminum cocatalysts,leading to the formation of polyethylenes with molecular weights of well above one million.Electron-donating substituents make the catalysts sensitive to polymerization temperature.In contrast,the catalysts bearing electron-withdrawing NO_(2) substituents show relatively steady performances at different temperatures.Most importantly,we demonstrate that different substituents and different positions both play important roles in determining the properties of nickel catalysts.This provides an alternative strategy for the future design of high-performance polymerization catalyst.
