Gold halide solutions

Reduced intensity curves, gold(III) halide solutions, 39 170... 

Fig. 5. Experimental s-i(s) values (crosses) for gold(III) halide solutions compared with theoretical values (solid lines) calculated for square-planar AuX4 complexes.

Fig. 6. Radial distribution functions, D(r), for the gold(III) halide solutions (solid lines), compared with calculated peaks (dots) for a square-planar AuX,t complex. The 47rr2p0 functions are shown by dotted lines. 

Results from Least-Squares Refinements of X-ray Diffraction Data for Gold(III) Halide Solutions... 

Fig. 5.68. SER spectra of a gold electrode in contact with various halide solutions (0.1 M), electrode potentials as indicated, Xq = 647 nm, Pq = 400 mW, resolution 7 cm ...

These extractants require the presence of stable anionic metal complexes to form the extractable ion pair complexes, so that only metals that produce such species can be extracted with these compounds. The ease of metal extraction follows the mag-nitnde of the formation coefQcient of the anionic complex. Thus, in halide solution, gold (III) > iron (III) > zinc > cobalt > copper > nickel. 

Halides. Gold(III) chloride [13453-07-1] can be prepared directiy from the elements at 200°C (167). It exists as the chlotine-bridged dimer, Au2Clg ia both the soHd and gas phases under an atmospheric pressure of chlorine at temperatures below 254°C. Above this temperature ia a chlorine atmosphere or at lower temperatures ia an iaert atmosphere, it decomposes first to AuCl [10294-29-8] and then to gold. The monochloride is only metastable at room temperature and slowly disproportionates to gold(0) and gold(III) chloride. The disproportionation is much more rapid ia water both for AuCl and the complex chloride, [AuCy, formed by iateraction with metal chlorides ia solution. 

As well as the adsorption of halogen atoms or molecules, the adsorption of halide anions to gold surfaces has been extensively studied and a comprehensive review of the area has been published by Magnussen [168]. The degree of specific adsorption to gold surfaces increases in the order F < Cl < Br < 1 with only weakly specifically adsorbed. The presence of halide anions can also affect the electrodeposition of organic molecules such as pyridine on Au surfaces with chloride and bromide solutions suppressing the formation of ordered N-bonded pyridine layers [169]. 

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... 

The structure of the metal particles dispersed on a silica powder support ( Aerosil 380, 70 A average silica particle diameter) has been studied by Avery and Sanders (47) using electron microscopy in both bright and dark field, to determine the extent to which the metal particles were multiply twinned or of ideal structure. Platinum, palladium, and gold were examined. These catalysts were prepared by impregnation using an aqueous solution of metal halide derivatives, were dried at 100°-150°C, and were hydrogen... 

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