New catalyst design for polymerization of norbornene esters by reducing intramolecular interaction

We have used density functional theory to study palladium-based catalysts commonly used for the polymerization of norbornene derivatives with an ester group. Exo–exo, exo–endo, and endo–endo isomers of catalyst complexes were investigated; the endo–endo isomer was the most stable and inactive due to an intramolecular interaction between Pd and O of the carbonyl group. Phosphine groups are effective in minimizing the Pd–O interaction in the endo–endo isomer and P(C6H11)3 was found to be the most efficient reagent. The intramolecular Pd–O interactions were estimated using model complexes, and it was demonstrated that they play a crucial role in stabilizing the endo–endo isomer.