Formula CrO5 | ||
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Chromium(VI) peroxide (CrO5) or chromium oxide peroxide is an unstable compound 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) peroxide is formed. Chromate or dichromate reacts with hydrogen peroxide and an acid to give chromium peroxide and water.
CrO42− + 2 H2O2 + 2 H+ → CrO5 + 3 H2OAfter a few seconds, the chromium(VI) peroxide decomposes to turn green as chromium(III) compounds are formed. To avoid this decomposition, it is possible to stabilize chromium(VI) oxide peroxide in a water-immiscible organic solvent such as diethyl ether, butan-1-ol or amyl acetate by adding a layer of the organic solvent above the chromate/dichromate solution and shaking during the addition of hydrogen peroxide. In this way, the chromium(VI) peroxide (unstable in the aqueous phase in which newly formed) is dissolved in the immiscible organic solvent. In this condition it can be observed over a much longer period.
2 CrO5 + 7 H2O2 + 6 H+ → 2 Cr3+ + 10 H2O + 7 O2This compound contains one oxo ligand and two peroxo ligands, making a total of five oxygen atoms per chromium atom.
Derivatives
The etherate, bipyridyl and pyridyl complexes of this compound have been found to be effective oxidants in organic chemistry. The structure of the pyridyl complex has been determined crystallographically.