Abstract: A series of phosphinophenolate neutral nickel catalysts bearing pyridine as spectator ligands(2-P(R1)(R2)-C6H3(R)O)Ni(Me)(Py)(3a, R=H, R1=R2=Ph; 3b, R=t-Bu, R1=R2=Ph; 3c, R=R1=R2=Ph; 3d, R=anthr, R1=R2=Ph; 3e, R=R1=t-Bu, R2=Ph) have been synthesized and characterized by 1H, 13C and 31P NMR. As a kind of single component catalysts, other than 3a they all showed a higher catalitic activty to ethylene polymerization reaction, and a high catalytic activity up to 4460 kg PE/(mol(Ni)·h) was achieved by introducing proper steric effection groups at ortho position of its phenoxy group(3c~3d). Molecular mass of the polymer can be adjusted by varying the substituents as the ortho-position of phenoxy group, and using catalysts 3c~3d with aryl substituents in ethylene polymerization reaction could produced higher molecular mass polymer. Catalyst 3e with a tert-butyl group at its phosphorous atom showed similar activity as that of catalyst 3b and was more readily initiated, producing polymers of lower molecular msses under the same conditions. Moreover, these catalysts were tolerant towards polar groups and able to catalyze copolymerization of ethylene with norbornene or its polar derivative 5-norbornene-2-yl-acetate.

Key words: Neutral nickel catalyst, ethylene polymerization, polar group tolerance, single component catalyst