Nickel Catalysts for Non‐Alternating CO‐Ethylene Copolymerization

Transition metal‐catalyzed copolymerization of CO and ethylene has a strong inherent propensity to produce the strictly alternating copolymer. In this work, nickel catalysts capable of both homopolymerization of ethylene and alternating copolymerization of CO and ethylene are developed to explore the possibility of non‐alternating copolymerization of CO and ethylene under the assumption that comonomer incorporation in the polymer chain can be adjusted by the concentrations of the comonomers. Both polyketones with slightly more than 50 % ethylene and “polyethylenes” with a small amount of CO incorporation are obtained but only under carefully controlled conditions and in low yields. Nickel catalysts capable of both ethylene homopolymerization and ethylene‐CO alternating copolymerization are designed and developed with the aim of realizing ethylene‐CO non‐alternating copolymerization. The non‐alternating copolymerization is indeed achieved but only within a very narrow window of comonomer concentration ratio. Both polyketones with more than 50 % ethylene and polyethylenes with a small amount of CO incorporation are obtained.