Chromium(VI) oxide peroxide
{{Chembox
| Verifiedfields = changed
| verifiedrevid = 434965124
| ImageFile = CrO5L.svg
| ImageAlt =
| ImageCaption = Chromium(VI) oxide peroxide coordination complex
| ImageFile1 =
| IUPACName = Chromium(VI) oxide diperoxide
| OtherNames = {{ubl|Chromium(VI) oxide peroxide|Chromium pentoxide}}. chromium oxide peroxide, chromium(VI) oxide diperoxide
|Section1={{Chembox Identifiers
| CASNo_Ref = {{cascite|correct|CAS}}
| CASNo = 35262-77-2
| CASNo_Comment = applies to "CrO5", which exists only as adducts, see image
| ChEBI = 30726
| ChemSpiderID = 21865108
| Gmelin = 101104
| PubChem = 22222816
| SMILES = O0O[Cr]01(=O)OO1
| InChI = 1/Cr.5O/q;;;-2;2*-1/rCrO4.O/c2-1(3,4)5;/q2*-2
| InChIKey = ZWPVWTIRZYDPKW-NIUFNKCUAY }}
|Section2={{Chembox Properties
| Formula = {{chem2|CrO(O2)2}}
| Cr=1|O=5
| Appearance = Dark blue
| Solubility = soluble (decomposes)}}
|Section3={{Chembox Hazards
| MainHazards = May suddenly explode if unstabilized/dry, toxic and create highly carcinogenic chromium fumes.
}}
}}
Chromium(VI) oxide peroxide is a chemical compound with the chemical formula {{chem2|CrO(O2)2}}. The name "chromium(VI) oxide peroxide" is also given to a collection of chromium coordination complexes. They have the formula {{chem2|CrO(O2)2L}} where L is a ligand. These species are dark blue and often labile. They all feature oxo ligand and two peroxo ligands, with the remaining coordination sites occupied by water, hydroxide, diethyl ether, pyridine, or other Lewis bases.{{cite journal |doi=10.1016/S0020-1693(01)00747-2 |title=On the interaction of compounds of chromium(VI) with hydrogen peroxide. A study of chromium(VI) and (V) peroxides in the acid–basic pH range |date=2002 |last1=Gili |first1=Pedro |last2=Mederos |first2=Alfredo |last3=Lorenzo-Luis |first3=Pablo A. |last4=de la Rosa |first4=Eduardo Medina |last5=Muñoz |first5=Alfonso |journal=Inorganica Chimica Acta |volume=331 |pages=16–24}}
Preparation and properties
File:PyCrO5-from-xtal-1964-CM-3D-balls.png)}}. Hydrogen atoms bonded to carbon atoms are omitted. Color code: Cr = gray, C= black, H = white, O= red, N = blue.]]
Chromium(VI) oxide peroxide is formed by the addition of acidified hydrogen peroxide solutions to solutions of metal chromates or dichromates, such as sodium chromate or potassium dichromate. The generally yellow chromates or orange dichromates turn to dark blue as "chromium(VI) oxide peroxide" forms:
:{{chem2|CrO4(2−) + 2 H2O2 + H+ → [CrO(O2)2OH]- + 3 H2O}}
The structure of the pyridine complex has been determined crystallographically.{{cite journal | doi = 10.1038/196570b0 | title = Crystal Structure of Peroxochromates, CrO5⋅C5H5N | year = 1962 | last1 = Stomberg | first1 = Rolf | journal = Nature | volume = 196 | pages = 570–571 | issue=4854| s2cid = 4187294}} Adducts with other N-heterocycles have also been characterized similarly.{{cite journal |doi=10.3891/acta.chem.scand.22-1439 |title=The Crystal Structure of two Modifications of Oxidodiperoxido-2,2'-dipyridylchromium(VI), [CrO(O2)2(C10H8N2)] |date=1968 |last1=Stomberg |first1=Rolf |last2=Ainalem |first2=Ing-Britt |last3=Johansson |first3=Gunnar |last4=Tolboe |first4=O. |last5=Paasivirta |first5=Jaakko |journal=Acta Chemica Scandinavica |volume=22 |pages=1439–1451}}
Aqueous chromium(VI) oxide peroxide decomposes in a few seconds, turning green as chromium(III) compounds are formed.Holleman, Arnold F.; Wiberg, Egon; Wiberg, Nils; (1985). "Chromium" (in German). Lehrbuch der Anorganischen Chemie (91–100 ed.). Walter de Gruyter. pp. 1081–1095. {{ISBN|3-11-007511-3}}."
:{{chem2|2 CrO(O2)2 + 7 H2O2 + 6 H+ → 2 Cr(3+) + 10 H2O + 7 O2}}
Stable adducts of the type {{chem2|CrO(O2)2L}} include those with L = diethyl ether, 1-butanol, ethyl acetate, or amyl acetate. They form by adding a layer of the organic solvent above the chromate/dichromate solution and shaking during the addition of hydrogen peroxide.
{{clear|left}}
The etherate, bis(pyridine) and pyridine complexes of this compound have been found to be effective oxidants in organic chemistry.{{cite journal | doi = 10.1016/S0040-4020(01)87476-7 | title = Chromium(VI) based oxidants-1 Chromium peroxide complexes as versatile, mild, and efficient oxidants in organic synthesis | year = 1986 | last1 = Firouzabadi | first1 = H. | last2 = Iranpoor | first2 = N. | last3 = Kiaeezadeh | first3 = F. | last4 = Toofan | first4 = J. | journal = Tetrahedron | volume = 42 | pages = 719}}
{{chem2|CrO(O2)2}} is sometimes said to have a "butterfly-like" structure due to its arrangement according to valence bond theory.
Gallery
File:Solution of CrO5.jpg|An aqueous solution of "chromium peroxide"
File:CrO5.jpg|A dilute solution of "chromium peroxide"
File:Chromium(VI) oxide peroxide (stabilized in ether phase).jpg|"chromium(VI) oxide peroxide" in ether phase (above) and chromium(III) aqueous solution (below).
See also
- Tetraperoxochromate - an similarly-synthesized analogous chromium(V) peroxide complex
References
{{Reflist}}
External links
- [http://www.axel-schunk.de/experiment/edm0109.html Experimental details and photo] {{in lang|de}}
- {{YouTube |id=MjDgXQb4_DU |title=Losing fingers to chemistry}} (8 November 2012). Professor Martyn Poliakoff of the University of Nottingham demonstrates the synthesis on Periodic Videos.
{{chromium compounds}}