:Potassium tetraperoxochromate(V)
{{short description|Chemical compound}}
{{Chembox
| verifiedrevid = 431908114
| ImageFile = Potassium tetraperoxochrom.jpg
| ImageSize =
| IUPACName = Potassium tetraperoxochromate(V)
| OtherNames = {{ubl|Potassium perchromate|Potassium peroxochromate}}
|Section1={{Chembox Identifiers
| ChemSpiderID = 106513
| PubChem = 139134081
| CASNo_Ref = {{cascite|correct|??}}
| CASNo = 12331-76-9
| StdInChI=1S/Cr.3K.4O2/c;;;;4*1-2/q+5;3*+1;4*-2
| StdInChIKey = JSURYJVAXIVWCV-UHFFFAOYSA-N
| SMILES = [O-][O-].[O-][O-].[O-][O-].[O-][O-].[K+].[K+].[K+].[Cr+5]
}}
|Section2={{Chembox Properties
| Formula = {{chem2|K3[Cr(O2)4]}}
| MolarMass = 297.286 g/mol
| Appearance = black
| Density =
| MeltingPtC = 70
| MeltingPt_notes= (decomposes)
| BoilingPt =
| Solubility = Poorly soluble (0 °C)
Reacts (45 °C) }}
|Section7={{Chembox Hazards
| MainHazards =
| FlashPt =
| AutoignitionPt = }}
}}
Potassium peroxochromate, potassium tetraperoxochromate(V), or simply potassium perchromate, is an inorganic compound having the chemical formula {{chem2|K3[Cr(O2)4]|auto=1}}. It is a red-brown paramagnetic solid. It is the potassium salt of tetraperoxochromate(V), one of the few examples of chromium in the +5 oxidation state and one of the rare examples of a complex stabilized only by peroxide ligands.{{cite journal | first = V. S. | last = Sergienko | title = Structural chemistry of peroxo compounds of group VI transition metals: I. Peroxo complexes of chromium | journal = Crystallography Reports | year = 2007 | pages = 639–646 | doi = 10.1134/S1063774507040116 | volume = 52 | issue = 4 |bibcode = 2007CryRp..52..639S | s2cid = 95018505}} This compound is used as a source of singlet oxygen.{{cite journal |author1=John W. Peters |author2=Paul J. Bekowies |author3=Arthur M. Winer |author4=James N. Pitts Jr. |title=Potassium perchromate as a source of singlet oxygen |journal=Journal of the American Chemical Society |date=1975 |volume=97 |issue=12 |pages=3299–3306 |doi=10.1021/ja00845a003 |publisher=ACS Publications |language=English}}
Preparation
Potassium peroxochromate is prepared by treating potassium chromate with hydrogen peroxide at 0 °C:
:{{chem2|2 CrO4(2-) + 8 H2O2 → 2 [Cr(O2)4](2-) + 8 H2O}}
The intermediate tetraperoxochromate(VI) is reduced by hydrogen peroxide, forming tetraperoxochromate(V):{{cite web | url = http://deposit.ddb.de/cgi-bin/dokserv?idn=969592612&dok_var=d1&dok_ext=pdf&fi... | title = Preparation, Structure and Vibrational Spectroscopy of Tetraperoxo Complexes of CrV+, VV+, NbV+ and TaV+ | first = Gentiana | last = Haxhillazi | access-date = 2009-03-07 | archive-url = https://web.archive.org/web/20110718225714/http://deposit.ddb.de/cgi-bin/dokserv?idn=969592612&dok_var=d1&dok_ext=pdf&fi... | archive-date = 2011-07-18 | url-status = dead}}{{cite journal | first = E. H. | last = Riesenfeld |author2=Wohlers, H.E. |author3=Kutsch, W.A. | title = Höhere Oxydationsproducte des Chroms | journal = Berichte der Deutschen Chemischen Gesellschaft| year = 1905 | pages = 1885–1898 | doi = 10.1002/cber.190503802113 | volume = 38| issue = 2 | url = https://zenodo.org/record/1426142}}
:{{chem2|2 [Cr(O2)4](2-) + 2 OH- + H2O2 → 2 [Cr(O2)4](3-) + 2 H2O + O2}}
Thus, the overall reaction is:
:{{chem2|2 CrO4(2-) + 9 H2O2 + 2 OH- → 2 [Cr(O2)4](3-) + 10 H2O + O2}}
The compound decomposes spontaneously at higher temperatures.