Oxidation of gold

It has been suggested that gold does not have a stable surface oxide (227), and therefore, its surface can be cleaned simply by removing the physically and chemically adsorbed contaminants. However, more recently it has been shown that oxidation of gold by uv and ozone at 25°C gives a 1.7 0.4 — nm thick AU2O2 layer (228), stable to extended exposure to ultra high vacuum (UHV) and water and ethanol rinses. 

The action of alkali on aqueous Au " solutions produces a precipitate, probably of AU2O3.JCH2O, which on dehydration yields brown AU2O3. This is the only confirmed oxide of gold. It decomposes if heated above about 160°C and, when hydrous, is weakly acidic, dissolving in cone alkali and probably forming salts of the [Au(OH)4] ion. 

For example, AuCl immediately decomposes into gold and gold(III) chloride, though some gold(I) halide complexes such as Aul2 are quite stable, while Au(CN)2 is formed by oxidation of gold in the presence of CN ... 

AuCl3(tht) [129], AuX3[S(benzyl)2)2] (X = Cl, Br) [130] and AuC13 (thian-threne). Various dithiocarbamates and dithiolene complexes have been made, some by oxidation of gold(I) complexes (Figure 4.26). 

Perhalogenoaryls are more stable than the unsubstituted phenyls [176] and can be synthesized conveniently by oxidation of gold(I) complexes (demonstrating the stability of the Au-C bond). The initial product of oxidation addition seems to be the frans-isomer, which generally rearranges to the m-form ... 

Some gold(I) derivatives have been obtained with other type of /V-donor ligands as acetonitrile the compound [Au(NCMe)2]+ can be obtained by halide-catalyzed electrolysis of gold metal in MeCN.2412 This cation is very moisture sensitive and thermally labile, but the more stable cation [Au(NCPh)2]+ has been obtained by oxidation of gold with the nitrosyl cation in benzonitrile.2413 From EXAFS spectroscopic studies it has been suggested that the solvated gold(I) cations are tetra-coordinate in pyridine or acetonitrile solutions.2414 Other gold(I) complexes have been... 

An example of the very high sensitivity of the EQCM to mass change at the surface of the crystal is provided in the work of Bruckenstein and Shay (1985) on the electro-oxidation of gold in perchloric acid. 

Zanella R, Giogio S, Shin CH, Henry CR Louis C (2004) Characterization and reactivity in CO oxidation of gold nanoparticles supported on Xi02 prepared by deposition-preparation with NaOH and Urea. J Catal 222 257-267... 

JRuby Bed.—Six hundredweight of batch with about four ounces of oxide of gold. 

The washings and solution from the separated ter-oxide of gold may likewise be operated upon in a similar way, only that it is necessary to remove the nitrio acid before doing so. For this purpose, the liquid is evaporated, and the residue boiled for some time with an excess of hydrochloric acid til] nitrons acid ceases to be evolved. 

The next process is to tone it, that is, to substitute gold or oxide of gold, for the silver, which forms the shadows of the picture. This is done by immersing the print for two or three minutes in the following solution ... 

The acids H[AuCU] and H[AuBr4] are prepared by oxidation of gold in the presence of HC1 or HBr. The oxidant can be concentrated HNQ3, Cl2 or Br2, and many others or... 

Dithiols give several stable square planar gold(III) complexes. Some complexes of biochemical interest are those derived from 2,3-dimercaptopropanol (BAL),230 dimercaptosuc-cinic acid249 and penicillamine.542 These are thought to have structures similar to that of the toluenedithiolate derivative (72).543 They can be prepared by reaction of [AuCLJ- with the dithiol and base or by oxidation of gold in the presence of the dithiol. 

Halogen oxidation of gold(I) complexes can also give products involving reaction of phosphine substituents or give binuclear gold(III) complexes (equations 71 and 72).369,630... 

Thallium(III) compounds usually react to cause oxidation of gold(I), but in certain cases arylgold(I) species have been isolated [Eqs. (11) and (12)] (38, 39). Oxidative addition was prevented in the former due to the inability of X to form the necessary bridges in the intermediate species (J[Pg.45]

Gold-Catalyzed Oxidation of Carbon Monoxide. The oxidation of gold electrodes in alkaline media has been discussed in Chapter 10 and the electrochemical oxidation of CO, in Chapter 11. Because the intermediate involves... 

POSTER TITLE Atmospheric Oxidation of Gold-Bearing Pyrite Concentrates A Kinetics Study... 

First, a direct extension of this thinking leads to the conclusion that high oxidation states are most likely to be achieved in an anion, where, as a consequence of the electron-rich environment, the electronegativity of the high oxidation state is lower than in neutral or cationic species. This thought led to the discovery of the room temperature oxidation of gold and the platinum metals (all except rhodium react) using F2 in aHF made basic with alkali fluorides, described in Ref. 112. 

The room temperature oxidation of gold, ruthenium, osmium, iridium, platinum, or palladium with fluorine in anhydrous hydrogen fluoride... 

OXIDATION OF GOLD, RUTHENIUM, OSMIUM, IRIDIUM, PLATINUM, OR PALLADIUM 8 1 3... 

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