Dithionate

Not to be confused with dithionite.

The dithionate (or metabisulfate) anion, S
₂O²⁻
₆, is a sulfur oxoanion^[3] derived from dithionic acid, H₂S₂O₆. Its chemical formula is sometimes written in a semistructural format, as [O₃SSO₃]²⁻. It is the first member of the polythionates.

Dithionate

Skeletal formula of dithionate with assorted dimensions Ball and stick model of dithionate
Names
IUPAC name Dithionate
Systematic IUPAC name Bis(trioxidosulfate)(S—S)(2−)[1]
Identifiers
CAS Number	14781-81-8
3D model (JSmol)	Interactive image
ChEBI	CHEBI:29209
ChemSpider	2339557 Y
PubChem CID	3082075
CompTox Dashboard (EPA)	DTXSID60163807
InChI InChI=1S/H2O6S2/c1-7(2,3)8(4,5)6/h(H,1,2,3)(H,4,5,6)/p-2 Key: RMGVZKRVHHSUIM-UHFFFAOYSA-L
SMILES [O-][S+2]([O-])([O-])-[S+2]([O-])([O-])[O-]
Properties
Chemical formula	S 2O2− 6
Molar mass	160.126 g mol−1
Acidity (pKa)	0.5[2]
Conjugate acid	Dithionic acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

The sulfur atoms of the dithionate ion are in the +5 oxidation state due to the presence of the S–S bond. Generally, dithionates form stable compounds that are not readily oxidised or reduced. Strong oxidants oxidise them to sulfates and strong reducing agents reduce them to sulfites and dithionites.^[4] Aqueous solutions of dithionates are quite stable and can be boiled without decomposition.^[5]

The γ-irradiation of crystalline dithionates produces SO^•−
₃ radical ions.^[6] The unpaired electron in the SO^•−
₃ radical can be detected with electron paramagnetic resonance and barium dithionate has been proposed as the basis for a radiation dosimeter.^[7]

The dithionate ion can act as a bidentate ligand.^[8]

The structure of the dithionate ion in the solid state is staggered in Na₂S₂O₆·2H₂O, whereas in the anhydrous potassium salt it is nearly eclipsed.^[4]

Compounds

Compounds containing the dithionate ion include:

• sodium dithionate, Na₂S₂O₆
• potassium dithionate, K₂S₂O₆
• barium dithionate, BaS₂O₆

References

1. "Dithionate(2−) (CHEBI:29209)". Chemical Entities of Biological Interest (ChEBI). UK: European Bioinformatics Institute.
2. Perrin, D. D., ed. (1982) [1969]. Ionisation Constants of Inorganic Acids and Bases in Aqueous Solution. IUPAC Chemical Data (2nd ed.). Oxford: Pergamon (published 1984). Entry 63. ISBN 0-08-029214-3. LCCN 82-16524.
3. International Union of Pure and Applied Chemistry (2005). Nomenclature of Inorganic Chemistry (IUPAC Recommendations 2005). Cambridge (UK): RSC–IUPAC. ISBN 0-85404-438-8. p. 130. Electronic version.
4. Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
5. Cotton, F. Albert; Wilkinson, Geoffrey; Murillo, Carlos A.; Bochmann, Manfred (1999), Advanced Inorganic Chemistry (6th ed.), New York: Wiley-Interscience, ISBN 0-471-19957-5
6. Radiation Chemistry of Dithionates G.S. Murthy, R.L. Eager, and K.J. McCallum Can. J. Chem. 49(22),(1971), 3733
7. Barium dithionate as an EPR dosemeter Baran M.P., Bugay O.A., Kolesnik S. P., Maksimenko V. M., Teslenko V. V., Petrenko T. L. Desrosiers M. F. Radiation Protection Dosimetry 2006 120, 202; doi:10.1093/rpd/nci531
8. Structures of Some Copper (II) Complexes Containing S
   ₂O²⁻
   ₆ Ion Ishii M. Bulletin of the Yamagata University 5, 1,(2001), 7

External links

Media related to Dithionate ion at Wikimedia Commons