Thermodynamics of complex formation of silver(I) with N-donor ligands in non-aqueous solvents

The results of a potentiometric and calorimetric study on the complexation reactions of neutral N-donor ligands with silver(I) in propylenecarbonate (PC) and dimethylformamide (DMF) are reported. The ligands concerned in DMF are butylamine (n-but), 1,2-diaminoethane (EN), bis(2-aminoethyl)amine (DIEN) and N,N’-bis(2-aminoethyl)ethane-1,2-diamine (TRIEN) whereas in PC results are provided for EN and DIEN, because of side reactions occurring for n-but and TRIEN. The data are compared to those previously reported in dimethylsulfoxide (DMSO), acetonitrile (AN) and water solvent media which present quite different dielectric constants (ε) and donor numbers (Dn). The trend of stabilities of the mononuclear AgL and AgL2 formed is discussed in terms of different cation and amines solvation in the different solvents. TRIEN can form bimetallic species in DMF, but not in DMSO. Given the lower ε value for DMF than for DMSO, Ag2TRIEN formation is evidently more influenced by the lower solvation of Ag(I) ion in DMF, rather than by difference in dielectric constants of these two solvents. In PC in addition to mononuclear complexes of higher stability with respect to the former solvents, also polynuclear Ag2L and Ag3L2 species are found.