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. Heating this compound releases singlet oxygen.

Preparation

Potassium peroxochromate is prepared starting from chromium trioxide (CrO3), excess potassium hydroxide (KOH), and 30% hydrogen peroxide (H2O2):

2 KOH + CrO3 → K2CrO4 + H2O

Hydrogen peroxide is added at temperatures below −5 °C (23 °F; 268 K):

2 K2CrO4 + 8 H2O2 → 2 K2[Cr(O2)4] + 8 H2O

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

2 K2[Cr(O2)4] + 2 KOH → 2 K3[Cr(O2)4] + H2O2

Thus, the overall reaction is:

2 K2CrO4 + 7 H2O2 + 2 KOH → 2 K3[Cr(O2)4] + 8 H2O

The compound decomposes spontaneously at higher temperatures but may be stored in sealed containers for extended periods.