Favorable Propylene-Incorporated Terpolymerization of Ethylene with CO Mediated by Cationic [P,O]-Pd and Ni Complexes

Commercial polyketone materials are generally produced by palladium-catalyzed terpolymerization of ethylene and alpha-olefin with carbon monoxide (CO), and rare examples were reported regarding the incorporation of propylene into an ethylene/CO copolymer chain using a cost-effective nickel catalyst. In this study, we have developed a series of [P,O]-type cationic Pd and Ni complexes supported by a diphosphazane monoxide (PNPO) platform, and the electronic and steric effect on phosphine, amine, and phosphine oxide moieties is systematically investigated for terpolymerization in terms of activity, propylene/CO (C3) incorporation, and molecular weight control. It is observed that the melting temperature (Tm) is proportional to the number of C3 incorporations present in the polymer chain, and the incorporated propylene does not affect the degradation temperature substantially, thus broadening the processing temperature window of the resultant polyketones. Notably, in comparison with dppp-type catalysts, PNPO catalysts exhibited a higher preference for propylene consumption, which is of great importance for making more efficient use of alpha-olefin resources.

Automated summary

In this study, propylene was successfully incorporated into an ethylene/CO copolymer chain using a cost-effective nickel catalyst. The electronic and steric effect of different moieties in the catalyst was systematically investigated for terpolymerization. It was observed that the melting temperature (Tm) of the resulting polyketones was proportional to the amount of propylene incorporated into the polymer chain, without significant impact on the degradation temperature. The PNPO catalysts showed higher preference for propylene consumption compared to dppp-type catalysts, which is important for efficient utilization of alpha-olefin resources.