Transition Metal Thiosulfate Complex on:
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A transition metal thiosulfate complex is a 
coordination complex
A coordination complex consists of a central atom or ion, which is usually metallic and is called the ''coordination centre'', and a surrounding array of bound molecules or ions, that are in turn known as ''ligands'' or complexing agents. Many ...
containing one or more thiosulfate
Thiosulfate ( IUPAC-recommended spelling; sometimes thiosulphate in British English) is an oxyanion of sulfur with the chemical formula . Thiosulfate also refers to the compounds containing this anion, which are the salts of thiosulfuric acid, ...
ligands. Thiosulfate occurs in nature and is used industrially, so its interactions with metal ions are of some practical interest. Three binding modes are common: monodentate (κ1-), ''O'',''S''-bidentate (κ2-),and bridging (μ-). Typically, thiosulfate complexes are prepared from thiosulfate salts. In some cases, they arise by oxidation of polysulfido complexes, or by binding of sulfur trioxide to sulfido ligands.
Applications
Silver-thiosulfate complexes are produced by commonphotographic fixer
Photographic fixer is a mix of chemicals used in the final step in the photographic processing of film or paper. The fixer stabilises the image, removing the unexposed silver halide remaining on the photographic film or photographic paper, leavi ...
s. By dissolving silver halide
A silver halide (or silver salt) is one of the chemical compounds that can form between the Chemical element, element silver (Ag) and one of the halogens. In particular, bromine (Br), chlorine (Cl), iodine (I) and fluorine (F) may each combine wi ...
s the fixer stabilises the image. The dissolution process entails reactions involving the formation of 1:2 and 1:3 complexes (X = halide): Fixation involves these chemical reactions (X = halide
In chemistry, a halide (rarely halogenide) is a binary chemical compound, of which one part is a halogen atom and the other part is an element or radical that is less electronegative (or more electropositive) than the halogen, to make a f ...
, typically ):Karlheinz Keller et al. "Photography" in Ullmann's Encyclopedia of Industrial Chemistry, 2005, Wiley-VCH, Weinheim.
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Sodium aurothiosulfate
Sodium aurothiosulfate, or sanocrysin, is the inorganic compound with the formula . This salt contains an anionic coordination complex of gold(I) bound to two thiosulfate ligands. It is colorless.
History
The compound was first synthesized in 1 ...
dihydrate, , has been widely discussed in the context of the extraction of gold
Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile ...
from its ores. Presently cyanide
Cyanide is a naturally occurring, rapidly acting, toxic chemical that can exist in many different forms.
In chemistry, a cyanide () is a chemical compound that contains a functional group. This group, known as the cyano group, consists of ...
salts are used on a large scale for this purpose with obvious risks.
Naming
In theIUPAC Red Book
Nomenclature of Inorganic Chemistry, IUPAC Recommendations 2005 is the 2005 version of '' Nomenclature of Inorganic Chemistry'' (which is informally called the Red Book). It is a collection of rules for naming inorganic compounds, as recommended by ...
the following terms may be used for thiosulfate as a ligand: trioxido-1κ3''O''-disulfato(''S''—''S'')(2−); trioxidosulfidosulfato(2−); thiosulfato; sulfurothioato. In the naming for thiosulfate salts, the final "o" is replaced by "e".IUPAC Red Book p 329 Thus, sodium aurothiosulfate could be called trisodium di(thiosulfato)aurate(I).
References