Comparative Study on Catalytic Systems for the Alternating and Nonalternating CO/Ethene Copolymerization

Drent et al. [Chem. Commun. 2002, 9, 964] have recently shown that a neutral (P−O)Pd(II) catalyst based on o-alkoxy derivatives of diphenylphosphinobenzene sulfonic acid (1a) can perform nonalternating CO/C2H4 copolymerization in which the resulting polyketone can have one or more subsequent ethylene units. We have analyzed this catalyst by comparing it to a cationic palladium catalyst, [(P−P)Pd(II)+] (1c), (P−P) = dppp = Ph2P−(CH2)3−PPh2, that affords polyketones with strictly alternating CO and C2H4 units. We have also investigated a derivative (1b) of 1a in which the o-methoxy substituents were replaced by a o-isopropyl group in order to investigate whether increasing the steric bulk enhances the degree of nonalternation.