Interaction of (dien)Pd(II) with cytidine and cytidine 5'-monophosphate. Influence of the phosphate group on the kinetics and mechanism.

The kinetics and the equilibrium of (dien)PdCl+ interaction with cytidine (C) and cytidine 5'-monophosphate (CMP) were studied by spectrophotometry and by stopped-flow methods. In both cases, the mechanism implies a (dien)Pd(H2O)2+ intermediate with a significant contribution of the solvent path at low chloride concentrations. With CMP, the rate is affected due to the addition of a mechanistic path via an intermediate formed between (dien)Pd(II) and the phosphate group of CMP. The kinetic and thermodynamic parameters have been determined and reflect the favorable electrostatic interactions due to the presence of the phosphate group of CMP. Furthermore, these parameters are in agreement with a transient (dien)Pd(II)-phosphate complex of CMP leading to the formation of the thermodynamically favored (dien)Pd(II)-N3 complex as final product.