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Copper peroxide
View on Wikipedia| Names | |
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| IUPAC name
Copper(II) peroxide
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| Identifiers | |
3D model (JSmol)
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| ChemSpider | |
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| Properties | |
| CuO2 | |
| Molar mass | 95.945 g/mol |
| Appearance | Dark olive-green solid |
| Related compounds | |
Related compounds
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Copper(IV) oxide |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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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+O−2.[1]
History
[edit]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.[2] The Schweizer's reagent used must not contain excess ammonia.[2]
It was once claimed to result from the very slow reaction of finely divided cupric oxide with cold hydrogen peroxide.[3]
Several molecular copper peroxide complexes have been reported, but these species always feature supporting organic ligands.[4]
References
[edit]- ^ Gutsev, G. L.; Rao, B. K.; Jena, P. (2000). "Systematic Study of Oxo, Peroxo, and Superoxo Isomers of 3d-Metal Dioxides and Their Anions". The Journal of Physical Chemistry A. 104 (51): 11961–11971. Bibcode:2000JPCA..10411961G. doi:10.1021/jp002252s.
- ^ a b The Collected Works of Sir Humphry Davy: Discourses delivered before the Royal society. Elements of agricultural chemistry, pt. I. The Chemical Society (Great Britain). 1894. p. 32.
- ^ Krüss, Gerhard (1884). "Einige Beobachtungen über die höheren Sauerstoffverbindungen des Kupfers" (abstract). Ber. 17 (2): 2593–2597. doi:10.1002/cber.188401702186.
- ^ Elwell, Courtney E.; Gagnon, Nicole L.; Neisen, Benjamin D.; Dhar, Debanjan; Spaeth, Andrew D.; Yee, Gereon M.; Tolman, William B. (2017). "Copper–Oxygen Complexes Revisited: Structures, Spectroscopy, and Reactivity". Chemical Reviews. 117 (3): 2059–2107. doi:10.1021/acs.chemrev.6b00636. PMC 5963733. PMID 28103018.
Copper peroxide
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Definition and nomenclature
Copper peroxide is an inorganic compound nominally represented by the formula CuO₂, consisting of copper in the +2 oxidation state bonded to a peroxide ligand (O₂²⁻). It is commonly referred to as copper(II) peroxide to explicitly indicate the oxidation state of copper.[4] This nomenclature distinguishes it from copper oxides, such as copper(I) oxide (Cu₂O) and copper(II) oxide (CuO), in which oxygen exists as discrete oxide ions (O²⁻) rather than as a peroxide unit, and from potential copper superoxides involving the superoxide anion (O₂⁻).[5] The oxidation state in copper peroxide is formally Cu²⁺ with O₂²⁻, though spectroscopic analyses of related copper-oxygen species sometimes suggest an alternative Cu⁺ O₂⁻ superoxide description depending on coordination and bonding.[6] Actual isolated species referred to as copper peroxides include basic copper peroxide, with the approximate formula CuO·H₂O₂ (or CuO₂·H₂O), which is an adduct of copper(II) hydroxide and hydrogen peroxide rather than a stoichiometric peroxide and thus misnamed as a pure peroxide compound.[7] Another related species is Cu₂O₂, known as dicopper peroxide or copper(I) peroxide, featuring two Cu⁺ ions with a peroxide ligand, but it is often misnamed due to structural ambiguities and instability leading to oxide-like behavior.[8]Hypothetical nature and related compounds
Pure copper peroxide (CuO₂) remains a hypothetical compound, as it has not been isolated in a stable, pure crystalline form owing to its thermodynamic instability and propensity to decompose into copper(II) oxide (CuO) and molecular oxygen (O₂). Although recent advances have enabled the synthesis of CuO₂ in nanoscale forms, such as nanodots for specific applications, these are stabilized by their size and environment rather than representing bulk material, underscoring the challenges in achieving a persistent solid phase. Computational studies on the gaseous CuO₂ molecule support its peroxide-like character, predicting a bent or side-on geometry where the peroxo (O₂²⁻) unit binds to Cu(II). These calculations indicate a peroxo coordination mode, though the overall structure is energetically unfavorable relative to decomposition products.[9] Such modeling highlights the kinetic barriers that prevent isolation under standard conditions. Related to the ideal CuO₂, basic copper peroxide is the most commonly referenced analog, with an approximate formula of CuO·H₂O₂ (or CuO₂·H₂O). This compound forms as a yellow-brown amorphous solid upon reaction of copper(II) salts with hydrogen peroxide under cold, neutral conditions, but it exhibits limited stability, decomposing more rapidly when moist and slowly in dry form to release H₂O₂ or evolve O₂.[7] Anhydrous Cu₂O₂, envisioned as a peroxide-bridged dimer with a rhomboidal Cu₂O₂ core, has been characterized computationally and in transient species but lacks isolation as a discrete bulk compound; instead, it manifests in stabilized molecular complexes. These complexes, such as [Cu(η²-O₂)] with supporting ligands like β-diketiminates or hydrotris(pyrazolyl)borates, demonstrate enhanced stability through coordination, allowing reversible O₂ binding and spectroscopic characterization of the peroxo moiety.| Compound | Formula | Color | Stability |
|---|---|---|---|
| Pure copper peroxide | CuO₂ | N/A (hypothetical) | Thermodynamically unstable; decomposes to CuO + ½O₂ |
| Basic copper peroxide | CuO·H₂O₂ | Yellow-brown, amorphous | Moderately unstable; dry form decomposes slowly, moist form faster |
| Anhydrous copper peroxide | Cu₂O₂ | N/A (dimeric core) | Unstable in isolation; stable in ligand-supported molecular complexes |
