Gold complexes thiolates

Bardaji, M., Laguna, A., Perez, M.R. and Jones, P.G. (2002) Unexpected Ring-Opening Reaction to a New Cyanamide-Thiolate Ligand Stabilized as a Dinuclear Gold Complex. Organometallics, 21(9), 1877-1881. 

The earliest use of gold complexes in medicine primarily involved gold thiolates, which being yellow or even gold-colored in solution, led to their designation as chrysotherapy (chrysos is Greek for gold). 

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]. 

Hill, D.T, Sutton, B.M., Isab, A.A., Razi, T, Sadler, P.J., Trooster, J.M. and Calls, G.H.M. (1983) Gold- 197 Mossbauer Studies of Some Gold(I) Thiolates and Their Phosphine Complexes Including Certain Antiarthritic Gold Drugs. Inorganic Chemistry, 22, 2936-2942. 

Scheme 1. The solvent-free controlled thermolysis of gold(I) thiolate complex producing gold nanoparticles stabilized by alkyl groups derived from the precursor.

Scheme 2. Production of size-regulated gold nanoparticles stabilized by primary amines, tertiary amines, sulfides, and thiols formed by the controlled thermolysis of gold(I) thiolate complex in the presence of amine (reprinted from Ref. [11], 2005, with permission from Elsevier).

Gold(I) thiolate complexes have different stoichiometries, the neutral [Au(SR)(PR3)] complexes are very numerous and have been synthesized for a great variety of thiolate and tertiary phosphine ligands. The phosphine is usually PPh3 (otherwise state) and the substituent R in the thiolate moiety can be Me (PMe3),2779 Ph (PR 3 PPh3, TPA),2780-2784 2,4,6-C6H2R23 (R2 = Me,... 

Negishi Y, Nobusada K, Tsukuda T (2005) Glutathione-protected gold clusters revisited bridging the gap between gold(I)-thiolate complexes and thiolate-protected gold nanocrystals. J Am Chem Soc 127 5261-5270... 

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... 

Gold(I) thiolates have important applications in gold coating and in the treatment of rheumatoid arthritis. There has been intensive research on these complexes, and excellent reviews have been published.9-14 The reader is referred to Chapter 62.2 for a review of medicinal applications. 

Similar thiolate exchange reactions have been shown to occur in complex (18), 244,264,273 and displacement of chloride (and phosphine) from [AuCl(PEt3)] was also established (equation 33).264,265 The gold(I) thiolate can displace weakly bonded ligands from gold to give -thiolate derivatives (equation 34).265... 

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. ... 

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). 

Fig. 3. (A) Ring and (B) chain structures for gold(I) thiolate drugs such as aurothiomalate ( Myocrisin )- Wide-angle X-ray scattering measurements have revealed Au-Au contacts of 3.35, 5.8, and 8.1 A, and analysis of the fine structure on the Au Lin X-ray absorption edge gives an average Au-S distance of 2,3 A with a coordination number of two (sulfurs) (54, 52). (C) White blood cells (PMNs) can covert aurothiomalate into [Au(CN)2], an inhibitor of O2 production (the oxidative burst) (62). This could provide a route to Au(III) dicyano complexes.

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