Tetrathionate

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The tetrathionate anion, S₄O₆²⁻, is a sulfur oxoanion derived from the compound tetrathionic acid, H₂S₄O₆. Two of the sulfur atoms present in the ion are in oxidation state 0 and two are in oxidation state +5. Alternatively, the compound can be viewed as the adduct resulting from the binding of the Lewis base S₂²⁻ to SO₃. Tetrathionate is one of the polythionates, a family of anions with the formula [S_n(SO₃)₂]²⁻.

Tetrathionate is a product of the oxidation of thiosulfate, S₂O₃²⁻, by iodine, I₂:

2S₂O₃²⁻ + I₂ → S₄O₆²⁻ + 2I⁻

Structure

Tetrathionate's structure can be visualized as following three edges of a cube, as in the diagram below. The structure shown is the configuration of S₄O₆²⁻ in BaS₄O₆·2H₂O and Na₂S₄O₆·2H₂O. Dihedral S-S-S angles approaching 90° are common in polysulfides.

Compounds

Compounds containing the tetrathionate anion include sodium tetrathionate, Na₂S₄O₆, potassium tetrathionate, K₂S₄O₆, and barium dithionate dihydrate, BaS₄O₆·2H₂O.

References

• Greenwood, N. N.; Earnshaw, A. (1997). Chemistry of the Elements, 2nd Edition, Oxford:Butterworth-Heinemann. ISBN 0-7506-3365-4.