Complex formation equilibria between Ag(I) amd thioureas in n-propanol

Complex formation equilibria between Ag(I) and thiourea or N-alkyl-substituted thioureas have been investigated in n-propanol by potentiometry at 10 degrees C intervals from 5 to 50 degrees C. Stepwise formation of tris-coordinated AgLn (n = 1-3) complexes has been found for the majority of the ligands. Delta H and Delta S values for the complex formation reactions have been evaluated from the dependence of ln beta(n) on temperature. The alkyl-substituents affect the ligand affinities in different ways in relation with the coordination level n. The reactions are exothermic with few exceptions. Enthalpy favoured complex formation with negative dependence of Delta G on temperature (Delta S>0) have been found. The enthalpy and entropy changes for the stepwise complex formation equilibria are correlated by two linear compensative relationships with the same isoequilibrium temperature 50-51 degrees C.