THERMODYNAMIC AND SPECTROSCOPIC STUDIES ON THE COMPLEXATION OF SILVER(I) BY MIXED PHOSPHORUS-SULFUR COMPOUNDS IN PROPYLENE CARBONATE - CRYSTAL AND MOLECULAR-STRUCTURE OF A SILVER(I)-THIOPHOSPHINE COMPLEX

The thermodynamic parameters for complexation of silver(I) with the mi xed-donor compounds Ph(2)PCH(2)SPh and Ph(2)P(CH2)(2)SR (R = Me, Et or Ph) have been determined by potentiometric and calorimetric technique s in propylene carbonate at 25 degrees C and 0.1 mol dm(-3) ionic stre ngth (NEt(4)ClO(4)). Within the silver(I) concentration range investig ated, Ph(2)PCH(2)SPh forms three successive mononuclear complexes wher eas also polynuclear species are formed by the other thiophosphines. A ll the complexes are strongly enthalpy stabilized, the entropy changes being unfavourable. The ligands behave as either monodentate (through P) or bidentate. depending upon the length of the aliphatic chain bet ween the donor atoms and on the stoichiometry of the species formed. T he influence of R on the stabilities of the complexes is discussed. Th e crystal structure of the 1:1 Ag-Ph(2)P(CH2)(2)SEt complex has been d etermined: monoclinic. space group P2(1)/c, a = 8.924(2), b = 9.620(1) , c = 44.797(6) Angstrom, beta = 93.41(1)degrees and Z = 4. Phosphorus -31 NMR studies have also been performed to obtain additional informat ion on the nature and structure of the species formed. Comparison of t he thermodynamic data for formation of the silver(I) complexes with th e same ligands in dimethyl sulfoxide evidences a different behaviour o f the ligands in the two media: the results are discussed in terms of the different physicochemical properties of the two solvents.