Origin of ligand effects on reactivities of pincer-Pd catalyzed hydrocarboxylation of allenes and alkenes with formate salts a computational study  

      The origin of ligand effects on pincer-Pd catalyzed hydrocarboxylation of allenes and alkenes was investigated using density functional theory (DFT) calculations. The computations reveal that the CO₂ insertion into allylpalladium and benzylpalladium intermediates is the rate-determining step for both allene and alkene substrates. Distortion/interaction analysis indicates that CO₂ insertion into the benzylpalladium intermediate via a 3-membered transition state has larger distortion energy than that of CO₂ reacting with the allylpalladium intermediate through a 6-membered transition state. The linear relationships between the distortion energy and the activation energy are applicable for a series of PGeP-pincer ligands with different P-bound R substituents.