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.Figure Methyl ester norbornene complex for endo–endo isomers with P(C₆H₁₁)₃