Gold(I) complexes with tertiary phosphine sulfide ligands

Phosphine sulfides and their gold(I) complexes with general formula R3P=S-Au-X (X = Cl-, Br- or CN-) were prepared and characterized by elemental analyses, i.r. and P-31-n.m.r. spectroscopy. A decrease in the i.r. frequency of the P=S bond in the ligands upon complexation, is indicative of 'S' coordination to gold (I). The P-31-n.m.r. spectra revealed that electronegativity of the substituents and angles between them were the two most important factors influencing the P-31-n.m.r. chemical shifts. The phosphorus resonance was observed to be more downfield in alkyl substituted phosphine sulfides as compared to the aryl substituted phosphine sulfides. Ligand scrambling in the Cy3P=S-Au-CN complex in solution, to form [(Cy3P=S)(2)Au](+) and [Au(CN)(2)](-), was investigated by C-13 and N-15-n.m.r. spectroscopy. Equilibrium constants (K-eq) for scrambling of the Cy3P=S-Au-CN complex and for its analogue, Cy3P=Se-Au-CN were measured by integrating the C-13-n.m.r. at 297 K and were found to be 0.147 and 1.81 respectively.