Potassium tetraperoxochromate(V)

Potassium peroxochromate, potassium tetraperoxochromate(V), or simply potassium perchromate, is an inorganic compound having the chemical formula K3[Cr(O2)4]. 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. This compound is used as a source of singlet oxygen.

Preparation
Potassium peroxochromate is prepared by treating potassium chromate with hydrogen peroxide at 0 °C:
 * 2 CrO4(2-) + 8 H2O2 → 2 [Cr(O2)4](2-) + 8 H2O

The intermediate tetraperoxochromate(VI) is reduced by hydrogen peroxide, forming tetraperoxochromate(V):


 * 2 [Cr(O2)4](2-) + 2 OH- + H2O2 → 2 [Cr(O2)4](3-) + 2 H2O + O2

Thus, the overall reaction is:
 * 2 CrO4(2-) + 9 H2O2 + 2 OH- → 2 [Cr(O2)4](3-) + 10 H2O + O2

The compound decomposes spontaneously at higher temperatures.