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

Abstract

Complex formation equilibria between Ag(I) and thiourea or N-alkyl-substituted thioureas have been investigated in n-propanol by potentiometry at 10 °C intervals from 5 to 50 °C. Stepwise formation of tris-coordinated AgL n ( n = 1–3) complexes has been found for the majority of the ligands. Δ H and Δ S values for the complex formation reactions have been evaluated from the dependence of ln β 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 Δ G on temperature (Δ 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 °C.