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A transition metal thiosulfate complex is a coordination complex containing one or more thiosulfate ligands. Thiosulfate occurs in nature and is used industrially, so its interactions with metal ions are of some practical interest.[1][2] Three binding modes are common: monodentate (κ1-), O,S-bidentate (κ2-),and bridging (μ-).

Illustrative coordination complexes of thiosulfate.

Preparation[edit]

Typically, thiosulfate complexes are prepared from thiosulfate salts by displacement of aquo or chloro ligands.[2] In some cases, they arise by oxidation of polysulfido complexes, or by binding of sulfur trioxide to sulfido ligands.[3][4]

Applications[edit]

Silver-thiosulfate complexes are produced by common photographic fixers. By dissolving silver halides, the fixer stabilises the image. The dissolution process entails reactions involving the formation of 1:2 and 1:3 complexes (X = halide):[5] Fixation involves these chemical reactions (X = halide, typically Br−):[6]

AgX + 2 S2O2−3 → [Ag(S2O3)2]3− + X−
AgX + 3 S2O2−3 → [Ag(S2O3)3]5− + X−

Sodium aurothiosulfate dihydrate, Na3[Au(S2O3)2]·2H2O, has been discussed in the context of the extraction of gold from its ores. Presently cyanide salts are used on a large scale for that purpose with obvious risks.[7]

Naming[edit]

In the IUPAC Red Book the following terms may be used for thiosulfate as a ligand: trioxido-1κ3O-disulfato(S—S)(2−); trioxidosulfidosulfato(2−); thiosulfato; sulfurothioato. In the naming for thiosulfate salts, the final "o" is replaced by "e".[8] Thus, sodium aurothiosulfate could be called trisodium di(thiosulfato)aurate(I).

References[edit]

  1. ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 715. ISBN 978-0-08-037941-8.
  2. ^ a b Carter, Alan; Drew, Michael G.B (1999). "Synthesis and Structure of Some Cobalt(II), Cobalt(III) and One Nickel(II) Monomeric, Monodentate(S) Thiosulfato complexes. Trans and cis Structural Effects in the Cobalt(III) Complexes". Polyhedron. 18 (10): 1445–1453. doi:10.1016/S0277-5387(99)00004-2.
  3. ^ Kubas, G. J.; Ryan, R. R. (1984). "Reduction of Sulfur Dioxide by Cp2MH2 (M = Mo, W) to Cp2M(S2O3) and water. Molecular Structure and Reaction with Acids of an Organometallic Molybdenum-Thiosulfate Complex". Inorganic Chemistry. 23 (20): 3181–3183. doi:10.1021/ic00188a030.
  4. ^ Rakova, O. A.; Sanina, N. A.; Shilov, G. V.; Strelets, V. V.; Borzova, I. B.; Kulikov, A. V.; Aldoshin, S. M. (2001). "[Bu4N]2[Fe2(μ-S2O3)2(NO)4]: Synthesis, Structure, Redox Properties, and EPR Study". Russian Journal of Coordination Chemistry. 27 (9): 657–663. doi:10.1023/A:1017905723120.
  5. ^ Sowerby, A.L.M., ed. (1961). Dictionary of Photography: A Reference Book for Amateur and Professional Photographers. London: Illife Books Ltd. pp. 324–326.
  6. ^ Karlheinz Keller et al. "Photography" in Ullmann's Encyclopedia of Industrial Chemistry, 2005, Wiley-VCH, Weinheim. doi:10.1002/14356007.a20_001
  7. ^ Aylmore MG, Muir DM (2001). "Thiosulfate Leaching of Gold - a Review". Minerals Engineering. 14 (2): 135–174. doi:10.1016/s0892-6875(00)00172-2.
  8. ^ IUPAC Red Book p 329
source: https://en.wikipedia.org/wiki/Transition_metal_thiosulfate_complex

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