Substitution Kinetics of Palladium Pincer Complexes

Abstract: The substitution reaction of complexes, (PCNR)PdCl, where R = (methyl) (1), (ethyl) (2) and(propyl) (3), with iodide where studied in 1-10 mM LiCl in methanol. The substitution was followed under pseudo first order conditions with an excess of incoming and leaving ligand. The high reactivity of complex 1 was attributed to the low steric bulkiness of the methyl substituent. The order of reactivity of the complexes followed 1 > 2 ≈ 3. The large negative values reported for entropy of activation for the complexes confirmed an associative substitution mode. The substitution reaction proceeds via the solvolytic pathway.