Gold complexes with thiolates

D., Yang, C.-T, Ranford, J.D., Vittal, J.J. and Lee, P.F. (2003) Synthesis, characterization, and biological activities of 2-phenylpyridine gold(lll) complexes with thiolate ligands. Dalton Transactions, (17), 3376. 

Figure 1.71 Gold(lll) complexes with thiolate or selenolate ligands.

Cyclometallated gold(III) dihalide complexes also act as useful precursors for the synthesis of gold(III) complexes with thiolate and other sulfur donor ligands. The cyclometallated ligand stabilises the gold(III) centre towards reduction, which is important due to the reducing potential of sulfur-based ligands. 

Like the gold(I) thiolates discussed earlier, the position of the equilibrium depends upon the affinity of the thiols for gold(I) with the established sequence being AtgSH >TgSH > GSH >TmSH. This sequence corresponds to increasing pKsn [12] or by decreasing P NMR chemical shifts for the EtsPAuSR complex in aqueous solution [55]. 

Figure 22 Some thiolate gold(I) complexes with several secondary interactions.

The aim of this chapter is to review the chemistry of chalcogenolates in the last 10 years. The more recent reviews in this field included chalcogenolates of the s-block elements,13,14 early transition metal thiolates,15 metal complexes with selenolate and tellurolate ligands,16 copper(I), lithium and magnesium thiolates,17 functionalized thiolate complexes,18 19 pentafluorobenzenethiolate platinum group compounds,20 tellurium derivatives,21 luminescent gold compounds,22 and complexes with lanthanide or actinide.23... 

Apart from thiolate ligands, S, Se or -containing fulvalene derivatives have been employed as electron donors in the synthesis of gold complexes. The combination of tetrathiafulvalene, TTF, with the gold complex bis(pyrazine-2,3-diselenolate)aurate... 

These thiolate exchange reactions are thought to lead to incorporation of gold(I) to thiolate functions in proteins and enzymes, and thence to interfere with the inflammatory process. Thiols such as 2,3-dimercaptopropanol (BAL), iV-acetylcysteine and penicillamine have also been used in the treatment of gold toxicity. Protein-bound gold is mobilized by complexation to the added thiol and can then be excreted.250,273... 

Fig. 8 Gold(I) complexes 4a-g with thiolate ligand bearing donor-acceptor functionalities...

A series of dinuclear gold(I) thiolate complexes with crown ether pendants has been successfrdly employed to switch on and off the Au-Au interactions (shown in equation (8)), and, hence, the photoemission induced by ion-binding, which provides a new strategy for the design of chemosensors and luminescence signaling. ... 

Cys-34 also binds Au, Ag, Hg, Cd, and, to a lesser extent, Cu. Major interests in the unusual chemistry at this site include understanding the nature of bound pharmaceuticals, such as the antiarthritic auranohn, or other gold(l)-containing thiolates (Shaw, 1989). Other pharmaceutical interests involve reactions with non-metal-containing antibiotics and the recently identified complexation with nitric acid (Stamler et al., 1992). 

Neither Au(I) nor Au(III) aqua ions, [Au(H20)2] and [Au(H20)4] +, have been characterized in solution or the solid state. The diaqua Au(I) ion is unstable to disproportionation, and stabilization of Au(I) requires TT-acceptor ligands. The dicyano complex K[Au(CN)2], with the characteristic linear two-coordination found in the majority of Au(I) complexes, is very stable and was used with some success to treat tuberculosis at the beginning of the century. Toxic side effects were reduced with thiolate complexes such as aurothiomalate (10), and the French physician Forestier, in 1929, introduced gold(I) thiolates for the treatment of rheumatoid arthritis in the mistaken belief that the two diseases were related 51). 

---