Editing Copper (section)

===Copper(III) and copper(IV)===
Copper(III) is most often found in oxides. A simple example is potassium [[cuprate]], KCuO<sub>2</sub>, a blue-black solid.<ref>{{cite book|chapter=Potassium Cuprate (III)|title=Handbook of Preparative Inorganic Chemistry|edition=2nd|editor=G. Brauer|publisher=Academic Press|year=1963|location=NY|volume=1|page=1015}}</ref> The most extensively studied copper(III) compounds are the [[cuprate superconductor]]s. [[Yttrium barium copper oxide]] (YBa<sub>2</sub>Cu<sub>3</sub>O<sub>7</sub>) consists of both Cu(II) and Cu(III) centres. Like oxide, [[fluoride]] is a highly [[base (chemistry)|basic]] [[anion]]<ref>{{cite journal|author1=Schwesinger, Reinhard |author2=Link, Reinhard |author3=Wenzl, Peter |author4=Kossek, Sebastian |title=Anhydrous phosphazenium fluorides as sources for extremely reactive fluoride ions in solution|doi=10.1002/chem.200500838|year=2006|journal=Chemistry: A European Journal|volume=12|issue=2|pages=438–45 |pmid=16196062}}</ref> and is known to stabilize metal ions in high oxidation states. Both copper(III) and even copper(IV) fluorides are known, [[Potassium hexafluorocuprate(III)|K<sub>3</sub>CuF<sub>6</sub>]] and [[Caesium hexafluorocuprate(IV)|Cs<sub>2</sub>CuF<sub>6</sub>]], respectively.<ref name="Holleman" />

Some copper proteins form [[oxo complex]]es, which, in extensively studied synthetic analog systems, feature copper(III).<ref>{{Cite journal |last1=Mirica |first1=Liviu M. |last2=Ottenwaelder |first2=Xavier |last3=Stack |first3=T. Daniel P. |date=2004-02-01 |title=Structure and Spectroscopy of Copper−Dioxygen Complexes |url=https://pubs.acs.org/doi/10.1021/cr020632z |journal=Chemical Reviews |language=en |volume=104 |issue=2 |pages=1013–1046 |doi=10.1021/cr020632z |pmid=14871148 |issn=0009-2665}}</ref><ref>{{cite journal |last1=Lewis |first1=E.A. |last2=Tolman |first2=W.B. |date=2004 |title=Reactivity of Dioxygen-Copper Systems |journal=Chemical Reviews |volume=104 |pages=1047–1076 |doi=10.1021/cr020633r |issue=2 |pmid=14871149}}</ref> With [[tetrapeptide]]s, purple-colored copper(III) complexes are stabilized by the deprotonated [[amide]] ligands.<ref>{{cite journal |last1=McDonald |first1=M.R. |last2=Fredericks |first2=F.C. |last3=Margerum |first3=D.W. |date=1997 |title=Characterization of Copper(III)–Tetrapeptide Complexes with Histidine as the Third Residue |journal=Inorganic Chemistry |volume=36 |pages=3119–3124|doi=10.1021/ic9608713|pmid=11669966 |issue=14}}</ref>

Complexes of copper(III) are also found as intermediates in reactions of organocopper compounds, for example in the [[Kharasch–Sosnovsky reaction]].<ref>{{Greenwood&Earnshaw2nd|page=1187}}</ref><ref>{{ cite journal | first1 = A. | last1 = Hickman | first2 = M. | last2 = Sanford | title = High-valent organometallic copper and palladium in catalysis | journal = Nature | volume = 484 | pages = 177–185 | year = 2012 | issue = 7393 | doi = 10.1038/nature11008 | pmid = 22498623 | pmc = 4384170 | bibcode = 2012Natur.484..177H }}</ref><ref>{{ cite journal | title = Well-defined organometallic Copper(III) complexes: Preparation, characterization and reactivity | first1 = He | last1 = Liu | first2 = Qilong | last2 = Shen | journal = [[Coordination Chemistry Reviews|Coord. Chem. Rev.]] | volume = 442 | year = 2021 | page = 213923 | doi = 10.1016/j.ccr.2021.213923}}</ref>