Copolymerization of Ethylene and Polar Monomers by Using Ni/IzQO Catalysts

The replacement of precious metals in catalysis by earth-abundant metals is currently one of the urgent challenges for chemists. Whereas palladium-catalyzed copolymerization of ethylene and polar monomers is a valuable method for the straightforward synthesis of functionalized polyolefins, the corresponding nickel-based catalysts have suffered from poor thermal tolerance and low molecular weight of the polymers formed. Herein, we report a series of neutral nickel complexes bearing imidazo[1,5-a]quinolin-9-olate-1-ylidene (IzQO) ligands. The Ni/IzQO system can catalyze ethylene polymerization at 50-100°C with reasonable activity in the absence of any cocatalyst, whereas most known nickel-based catalysts are deactivated at this temperature range. The Ni/IzQO catalyst was successfully applied to the copolymerization of ethylene with allyl monomers to obtain the corresponding copolymers with the highest molecular weight reported for a Ni-catalyzed system.