Commercial polyketone materials are
generally produced
by palladium-catalyzed
terpolymerization of ethylene and α-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
(T
m) 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 α-olefin
resources.