Tetrathionate
The tetrathionate anion, S
4O2−
6, 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 S2−
2 to SO3. Tetrathionate is one of the polythionates, a family of anions with the formula [Sn(SO3)2]2−. Its IUPAC name is (sulfonatodisulfanyl)sulfonate, the name of its corresponding acid is (sulfodisulfanyl)sulfonic acid. The Chemical Abstracts Service identifies tetrathionate by the CAS Number 15536-54-6.
Tetrathionate is a product of the oxidation of thiosulfate, S
2O2−
3, by iodine, I2:
Tetrathionate's structure can be visualized by following three edges of a cube, as in the diagram below. The structure shown is the configuration of S
4O2−
6 in BaS4O6·2H2O and Na2S4O6·2H2O. Dihedral S–S–S–S angles approaching 90° are common in polysulfides.
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