A detailed kinetic study was undertaken of the complex-formation reactions of Pd(en)Cl2 and Pd(Me4en)Cl2 (Me4en - N,N,N’,N’-tetramethylethylenediamine) with inosine and inosine 5’-monophosphate as a function of nucleophile and chloride concentrations. Two consecutive reaction steps could be observed for the Me4en complex. The kinetic data clearly demonstrate a changeover from steady-state to pre-equilibrium behavior on changing steric hindrance and the nature of the nucleophile. All complex-formation reactions proceed via the formation of reactive intermediates of the type [Pd(R4en)(Cl)H2O]+ and [Pd(R4en)(Nu)H2O]2+. The results are compared to available data for the corresponding Et4en system and allow a detailed discussion of the steric and nucleophilic control over the kinetics of such complex-formation reactions with representative DNA constituents.