THERMODYNAMIC AND SPECTROSCOPIC STUDIES ON SILVER(I) COMPLEX-FORMATION WITH PHOSPHORUS MULTIDENTATE LIGANDS IN DIMETHYL-SULFOXIDE

The thermodynamic parameters of complexation of silver(I) with bis(diphenylphosphino)methane (dppm), 1,2-bis(diphenylphosphino)ethane (dppe), 1,3-bis(diphenylphosphino)propane (dppp), bis(2-(diphenylphosphino)ethyl)phenylphosphine (etp), and tris(2-(diphenylphosphino)ethyl)phosphine (PP3), have been determined by potentiometric and calorimetric techniques in dimethyl sulfoxide (DMSO). The measurements have been conducted at 25 °C and 0.1 M ionic strength (NEt4ClO4). Dppm forms only polynuclear species in solution. Mononuclear complexes, in addition to polynuclear species, are by contrast formed with all other ligands. All complexes are formed in strongly exothermic reactions while the entropy changes are negative. The thermodynamic data indicate that, in the mononuclear complexes with silver(I), the ligands act as chelating agents. Very stable complexes of the type M2L2 are formed by dppm, dppe, and dppp: in these complexes, the diphosphines act as bridging ligands. Structural studies of solutions of silver(I) by means of 31P NMR technique confirm the conclusions drawn from the thermodynamic data about the nature and structure of the complexes formed in solution. Comparisons of the thermodynamic data relative to formation of silver(I) complexes with analogous ligands coordinating via nitrogen show that the silver(I) complexes with phosphorus donor ligands are far more stable than with nitrogen donor ligands. © 1990, American Chemical Society. All rights reserved.