Hydroxo-gold species

In spite of the low affinity for binding to oxygen, gold(III) alkoxo, hydroxo and even 0X0 complexes have been obtained [6, 7]. These are valuable models for Au-O(H) species which are likely to be involved in oxidation reactions catalyzed by metal-oxide-supported gold [8]. All these complexes have displayed interesting chemical reactivity and, in some cases, remarkable catalytic activity. 

Estimates of the total gold concentration vary but are typically 10"10-10 107M (in some cases 10 8M), and some have suggested that this is present as dispersed metal. Sillen (36) has considered this point and concluded that the metallic gold would not be stable for long periods in contact with sea water. The dissolved species would be AuC12 , mainly, with gold (III) as hydroxo species Au(OH)4", Au(OH)3C1-. This is... 

Gold(III), like Ptn, displays predominantly square coordination. Although there is little evidence for any persisting 5-coordinate complexes, there is no doubt that, as with Pt11 species, substitution reactions proceed via 5-coordinate intermediates. There is no evidence for a simple aqua ion, [Au(H20)4]3+, but mixed chloro-aqua and chloro-hydroxo complexes are formed by hydrolysis of [AuCI4]" Distorted octahedral coordination occurs rarely, [Au(en)2Cl2]+ being an example. 

---