Synthesis, characterization and NMR studies of some gold(I) and silver(I) complexes with cyanide, thiones and selenones

A series of gold(I) and silver(I) complexes with various thiones and selenones have been prepared and characterized by elemental analysis, infra red (IR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy {lcub} 1H, 13C, 15N, 31P and 107Ag{rcub}. The general formulas of the complexes are; [R ₃PAuTu]Cl, [R₃PAuSeu]Cl, [>C=S-AuCN], [>C=Se-AuCN], [(>C=S)AgNO ₃] and [(>C=S)₂AgNO₃]. The spectral data of all these complexes are consistent with the sulfur or selenium coordination of the ligands (thiones and selenones respectively) to metal ion.; The IR studies of cyanogold(I) complexes of thiones and selenones show that some of these complexes exist as nonionic complexes [LAuCN] while the others exist as ionic species, [Au(L)₂]+[Au(CN)2]− in the solid state. However, in solution all these complexes undergo scrambling reactions exhibiting the equilibrium, 2[LAuCN] [Au(L)₂]+ + [Au(CN)₂] −. Separate resonances, observed for 13C 15N in [LAuCN] and [Au(CN)₂]− in both 13C and 15N NMR provide the evidence for this scrambling process. The equilibrium constants (K_eq) for these reactions were determined by the integration of 13C 15N resonances in 13C NMR.; Ligand exchange reactions of anti-rheumatic gold(I) complexes with some ligands of biological importance, have been studied using 13C, 15N and 31p NMR. It has been observed that gold(I) thiomalate, (AuStm)_n reacts with thiolated nucleosides (6-mercaptopurine {lcub}6-MP{rcub} and its derivatives) forming the complexes of the type, [>C=S-Au-Stm]. It is shown that two geometrical isomers are possible for the complex, [6-MP-Au-Stm]. The reaction of (AuStm)_n with diselenides is a redox reaction resulting in the formation of (Stm)₂. Auranofin undergoes ligand exchange reactions with thiones forming the complexes of the type, [Et₃P-Au-S=C<] + and [>C=S-Au-SATg]. The displaced SATg− is oxidized to its disulfide, (SATg)₂. However, some of the displaced Et₃P is oxidized to Et₃PO while the remaining reacts with thiones to form Et₃P-S=C< species, characterized by δ 31p of 1.0 ppm It is observed that thiourea (Tu) undergoes fastest exchange reactions with auranofin, while imidazolidine-2-thione (Imt) does the slowest among the thiones studied.