Equilibrium and kinetic data for the interaction of diaqua-(S-methyl-L-cysteine)palladium(II) with biologically relevant ligands

The complex-formation equilibria of [Pd(SMC)(H2O)(2)](+) (SMC = S-methyl-L-cysteine) with inosine, inosine-5'-monophosphate, guanosine-5'-monophosphate, L-glycine and 1,1-cyclobutanedicarboxylate have been studied. The stoichiometry and stability constants of the formed complexes are reported, and the concentration distribution of the various complex species has been evaluated as a function of pH. The kinetics and mechanism of the complex-formation reactions were studied as a function of nucleophile concentration, temperature and pressure. Two consecutive reaction steps, which both depend on the nucleophile concentration, were observed under all conditions. The negative entropies and volumes of activation support the operation of an associative complex-formation mechanism. The results are compared and discussed in reference to data reported for closely related systems in the literature.