Novel photoresponsive dinuclear nickel catalysts for ethylene (co)polymerization

Abstract

Compared with the conventional strategies of electronic and/or steric perturbation, catalytic olefin polymerization modulated by light irradiation or metal-metal cooperativity effect is a fascinating challenge that attracts considerable attention in the academic community. In this context, we design a strategy that could employ both effects to influence the polymerization process. Some dinuclear salicylaldimine and α-imino-ketone nickel complexes bearing a stiff-stilbene bridge were prepared, which could transfer between (E)-isomers and (Z)-isomers under ultraviolet irradiation. This isomerization can tune the electronic, steric and metal-metal cooperativity effects of the nickel catalysts. In this way, the catalytic activity, as well as polymer microstructures including molecular weight and branching density can be modulated in ethylene polymerization and copolymerization reactions. This strategy is generally applicable to other olefin polymerization catalytic systems and other types of transition metal mediated catalysis.