Oxidation state of gold

Guzman J, Gates BC. 2004. Catalysis by supported gold Correlation between catalytic activity for CO oxidation and oxidation states of gold. J Am Chem Soc 126 2672-2673. 

The complexes of gold are most readily classified according to the oxidation state of gold. This section will give a very brief summary of the oxidation states found for gold, to serve as an introduction to the more detailed treatment which follows. 

There are also a great number of gold complexes in which gold-gold or gold-metal bonds are present, in which the formal oxidation state of gold may be considered to be zero or fractional values close to zero. These complexes will be discussed in Sections 55.21-55.23. 

This section will review an extensive class of compounds containing two or more gold atoms in which the average oxidation state of gold is less than one. Several fine reviews on aspects of... 

Simon, G., Huang, H., Penner-Hahn, J.E. et al. (1999) Oxidation state of gold and arsenic in gold-bearing arsenian pyrite. American Mineralogist, 84, 1071-79. 

Since, very few people seem to be aware of the process of ageing in air, it is probable that some of the published results regarding the oxidation states of gold in dried samples are inaccurate, as well as the catalytic results, especially in oxidation of carbon monoxide (Chapter 6). Furthermore, Au111 can be reduced under the influence of radiation, especially when applied in high vacuum this may occur with electrons as in TEM204,208 and with photons as in XAFS (J.T. Miller, personal communication) and XPS,204 so that special care is needed to characterise unreduced samples. Ease of reduction may also depend on the kind of support, and materials made from an Au1 precursor may also suffer reduction. 

A New Oxidation State of Gold The Preparation and some Properties of... 

At the time of their discovery, Mossbauer spectroscopy offered an additional tool to both confirm the quinquevalent oxidation state of gold in these compounds and support the octahedral form predicted for the AuF anion. The 77. 3 keV Ml... 

The same quantity of electric charge that deposited 0.612 g of silver was passed through a solution of a gold salt, and 0.373 g of gold was deposited. What is the oxidation state of gold in this salt ... 

ESR has application primarily to the rather rare and somewhat unstable M(II) oxidation states of gold and silver, but is an important tool for demonstrating their presence unambiguously. 

Several reports of organo-gold compounds have been published. In these studies, the main concern was to establish the oxidation state of gold atoms and to deduce whether the XPS data are consistent with the proposed molecular structure. Some of the compounds studied are shown below. 

Baxendale, Fielden, and Keene (7) identified a transient lower oxidation state of silver obtained by reaction of Ag+ solutions with hydrated electrons or atomic H. In the present work, similarly, transient—i.e., chemically reactive species of the lower oxidation state of gold were obtained by reducing Au1. Kinetic properties of these species, which might be of zero valency have, moreover, been examined. 

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