The discovery of late transition metal Ni and Pd complexes has enabled for the time coordination-insertion copolymerization of ethylene and polar olefins. Unfortunately, their catalytic activity is significantly reduced in the presence of polar monomers, such as acrylic acid or vinyl acetate, compared to in the presence of non-polar monomers. It is proposed that the formation of six-membered chelate complexes is believed to disfavor monomer coordination and polymerization. As a new strategy to avoid coordination inhibition by polar monomers, we designed a new class of mononuclear nickel complexes that have pedant polyethylene glycol (PEG) chains that can coordinate with alkali metal ions. We propose that the alkali cations will provide an alternative binding site for polar functionalities, making it more favorable for the C=C double bond rather than the polar group of functional olefins to bind to the transition metal center. The structures of the heterobimetallic species were confirmed by X-ray crystallography. Our olefin polymerization studies indicate that the addition of alkali ions to the Ni complexes can modify their polymerization activity and tune the molecular weight and branching structures of their polymer product. The heterobimetallic complexes also exhibit the better polar group tolerance compared to their parent mononuclear complexes.

Heterobimetallic catalysts for ethylene homo- and copolymerization

254th National Meeting (2017)

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