Palladium(II)-Assisted Copolymerization of Ethylene and CO: Influence of the Chain End on the Regularity of the Polymer

A theoretical study based on nonlocal density functional theory has been carried out on the Pd(II)-assisted homogeneous catalytic copolymerization of olefin and carbon monoxide, where the catalytic center is modeled by Pd(II) coordinated to PH 2 CH CHPH 2 and the olefin is modeled by C 2 H 4 . The investigation concentrated on the energetics of the chain propagation mechanism in the presence of a copolymer chain end with a carbonyl group coordinated to the metal center. With CO misinsertion ruled out in a previous work, 1 the present investigation rules out ethylene misinsertion into a growing polyketone chain due to the lack of a thermodynamically stable ethylene π-complex and the high barrier (+78 kJ/mol) associated with insertion of ethylene into the Pd−C 2 H 4 COR bond. On the other hand, insertion of CO into a Pd−C 2 H 4 COR bond is favored by a rather stable CO precursor complex (−32 kJ/mol) and by a low activation barrier (+49 kJ/mol).