Phosphines, gold, reactions with thiols

These are relevant to both the oral absorption of gold and entry into cells. We compare auranofin with EtaPAuCl since reactions with thiols could lead to the same products if the EtaP-Au bond stays intact. EtaPAuCl could also be a product of auranofin reactions with HCl media in the stomach, although NMR investigations (21,22) suggest that slow deacetylation of the sugar is the major reaction under such conditions. We have also studied the bis(phosphine) species (Et3P)2AuCl. Not only is this orally-active (23), but curiously also appears as an intermediate via EtaP transfer reactions both in some model systems and in red cells. 

Again, the precise roles of coordination-compound chemical sensitizers, in most cases, are not understood. In fact, their effects may have little to do with their own coordination chemistry. Many simple salts of gold and other noble metals are effective sensitizers. They also may be added to solutions during silver halide precipitation to produce doped emulsions that have special properties. A variety of compounds that can act as ligands to metal ions are also effective alone as chemical sensitizers, the result of complicated oxidation-reduction, ion replacement and adsorption reactions on the silver halide grain surface. These include polyamines, phosphines and thioether- or thiol-containing compounds. The chemistry of these materials with the silver halide surface is discussed in the reference literature. 

---