Dithionate

{{Short description|Ion}}

{{Distinguish|dithionite}}

{{Chembox

| ImageFileL1 = Dithionate-2D-dimensions.png

| ImageFileL1_Ref = {{chemboximage|correct|??}}

| ImageSizeL1 = 121

| ImageNameL1 = Skeletal formula of dithionate with assorted dimensions

| ImageFileR1 = Dithionate-3D-balls.png

| ImageFileR1_Ref = {{chemboximage|correct|??}}

| ImageSizeR1 = 121

| ImageNameR1 = Ball and stick model of dithionate

| IUPACName = Dithionate

| SystematicName = Bis(trioxidosulfate)(S—S)(2−){{Cite web|title = Dithionate(2−) (CHEBI:29209)|url = https://www.ebi.ac.uk/chebi/searchId.do?chebiId=29209|work = Chemical Entities of Biological Interest (ChEBI)|location = UK|publisher = European Bioinformatics Institute}}

|Section1={{Chembox Identifiers

| CASNo = 14781-81-8

| PubChem = 3082075

| ChemSpiderID = 2339557

| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}

| ChEBI = 29209

| SMILES = [O-][S+2]([O-])([O-])-[S+2]([O-])([O-])[O-]

| StdInChI = 1S/H2O6S2/c1-7(2,3)8(4,5)6/h(H,1,2,3)(H,4,5,6)/p-2

| StdInChIKey = RMGVZKRVHHSUIM-UHFFFAOYSA-L

}}

|Section2={{Chembox Properties

| Formula = {{chem|S|2|O|6|2−}}

| MolarMass = 160.126 g mol⁻¹

| ConjugateAcid = Dithionic acid

| pKa = 0.5{{cite book|title=Ionisation Constants of Inorganic Acids and Bases in Aqueous Solution|editor-first=D. D.|editor-last=Perrin|edition=2nd|series=IUPAC Chemical Data|issue=29|publisher=Pergamon|location=Oxford|year=1982|publication-date=1984|orig-date=1969|lccn=82-16524|isbn=0-08-029214-3|at=Entry 63}}

}}

}}

The dithionate (or metabisulfate) anion, {{chem|S|2|O|6|2−}}, is a sulfur oxoanion{{RedBookRef|page=130}} 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.

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.{{Greenwood&Earnshaw}} Aqueous solutions of dithionates are quite stable and can be boiled without decomposition.{{Cotton&Wilkinson6th}}

The γ-irradiation of crystalline dithionates produces {{chem|SO|3|•−}} radical ions.Radiation Chemistry of Dithionates G.S. Murthy, R.L. Eager, and K.J. McCallum Can. J. Chem. 49(22),(1971), 3733 The unpaired electron in the {{chem|SO|3|•−}} radical can be detected with electron paramagnetic resonance and barium dithionate has been proposed as the basis for a radiation dosimeter.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}}

The dithionate ion can act as a bidentate ligand.Structures of Some Copper (II) Complexes Containing {{chem|S|2|O|6|2−}} Ion Ishii M. Bulletin of the Yamagata University 5, 1,(2001), 7

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.