Thermodynamic and spectroscopic studies on the complexation of silver(I) by 2-(diphenylphosphino)pyridine in dimethyl sulfoxide and propylene carbonate

The thermodynamic parameters for the Ag(I) complexation with the mixed, short-bite PN ligand 2-(diphenylphosphino)pyridine (Ph2Ppy) in dimethyl sulfoxide (dmso) and propylene carbonate (4-methyl-1,3-dioxolan-2-one, pc) have been determined by potentiometric and calorimetric techniques at 298 K and 0.1 mol dm−3 ionic strength (NEt4ClO4). Mononuclear complexes are formed both in dmso (AgLj +, j=1–3) and in pc (AgLj +, j=2, 3) where the ligands act as P donors. In pc, Ag2L2+, Ag2L2 2+ and Ag2L3 2+ dinuclear species are also formed in which the ligands are bridging in behavior. All the complexes are enthalpy stabilized whereas the entropy changes counteract the complex formation. 31P NMR and FT IR studies have also been performed to obtain some additional information on the coordination mode of the species formed. The results are discussed in terms of the steric requirements of the species and of the different physicochemical properties of the two solvents.