Copper peroxide

Copper peroxide is a hypothetical inorganic compound with the chemical formula CuO2. The 1:2 ratio of copper and oxygen would be consistent with copper in its common +2 oxidation state and a peroxide group. Although samples of this composition have not been isolated, CuO2 has attracted interest from computational perspective. One highly cited analysis concludes that gaseous CuO2 is a superoxide, with copper in a +1 oxidation state: Cu+O2-.

History
Species claimed to be "copper peroxide" have been claimed, e.g., by the reaction of cold solutions of Schweizer's reagent—a source of copper(II)—and hydrogen peroxide.. The Schweizer's reagent used must not contain excess ammonia.

It was once claimed to result from the very slow reaction of finely divided cupric oxide with cold hydrogen peroxide.

Several molecular copper peroxide complexes have been reported, but these species always feature supporting organic ligands.