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Cuprate loosely refers to a material that can be viewed as containing
anionic An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conven ...
copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...
complexes. Examples include tetrachloridocuprate ( uCl4sup>2−), the superconductor YBa2Cu3O7, and the organocuprates (e.g., dimethylcuprate u(CH3)2sup>−). The term cuprates derives from the Latin word for copper, ''cuprum''. The term is mainly used in three contexts: oxide materials, anionic
coordination complex A coordination complex consists of a central atom or ion, which is usually metallic and is called the ''coordination centre'', and a surrounding array of bound molecules or ions, that are in turn known as '' ligands'' or complexing agents. ...
es, and anionic
organocopper compound Organocopper compounds is the chemistry of organometallic compounds containing a carbon to copper chemical bond. Organocopper chemistry is the study of organocopper compounds describing their physical properties, synthesis and reactions. They a ...
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Oxides

One of the simplest oxide-based cuprates is the copper(III) oxide KCuO2, also known as "potassium cuprate(III)". This species can be viewed as the K+ salt of the polyanion []''n''. As such the material is classified as a cuprate. This dark blue diamagnetic solid is produced by heating potassium peroxide and copper(II) oxide in an atmosphere of oxygen: :K2O2 + 2 CuO → 2 KCuO2 Sodium cuprate(III) NaCuO2 and potassium cuprate(III) KCuO2 can also be produced by using hypochlorites or
hypobromite The hypobromite ion, also called alkaline bromine water, is BrO−. Bromine is in the +1 oxidation state. The Br–O bond length is 1.82 Å. Hypobromite is the bromine compound analogous to hypochlorites found in common bleaches, and in immune ce ...
s to oxidize copper hydroxide under alkaline and low temperature conditions. :2NaOH + CuSO4 → Cu(OH)2 ↓ :Cu(OH)2 + 2NaOH + NaClO → 2NaCuO2 + NaCl + :2NaOH + CuSO4 → Cu(OH)2 ↓ :Cu(OH)2 + 2KOH + KBrO → 2KCuO2 + KBr + Cuprates(III) are not stable in water, because they can oxidize water. :4 + 2 → 4CuO + ↑ + 4


Coordination complexes

Copper forms many anionic
coordination complex A coordination complex consists of a central atom or ion, which is usually metallic and is called the ''coordination centre'', and a surrounding array of bound molecules or ions, that are in turn known as '' ligands'' or complexing agents. ...
es with negatively charged ligands such as cyanide, hydroxide, halides, as well as alkyls and aryls.


Copper(I)

Cuprates containing copper(I) tend to be colorless, reflecting their d10 configuration. Structures range from linear 2-coordinate, trigonal planar, and tetrahedral. Examples include dichloro and trichlorocuprates, i.e., linear uCl2sup>− and trigonal planar uCl3sup>2−. Cyanide gives analogous complexes but also the trianionic tetracyanocuprate(I), u(CN)4sup>3−. Dicyanocuprate(I) exists in both molecular or polymeric motifs, depending on the countercation.


Copper(II)

The chlorocuprates include trichlorocuprate(II) uCl3sup>−, which is dimeric, square-planar tetrachlorocuprate(II) uCl4sup>2−, and pentachlorocuprate(II) uCl5sup>3−. 3-Coordinate chlorocuprate(II) complexes are rare. Tetrachlorocuprate(II) complexes tend to adopt flattened tetrahedral geometry with orange colors. Sodium tetrahydroxycuprate (Na2 u(OH)4 is an example of a homoleptic (all ligands being the same) hydroxide complex. :Cu(OH)2 + 2 NaOH → Na2Cu(OH)4


Copper(III) and copper(IV)

Hexafluorocuprate(III) uF6sup>3− and hexafluorocuprate(IV) uF6sup>2− are rare examples of copper(III) and copper(IV) complexes. They are strong
oxidizing agent An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or " accepts"/"receives" an electron from a (called the , , or ). In other words, an oxi ...
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Organic cuprates

Cuprates have a role in organic synthesis. They are invariably Cu(I), although Cu(II) or even Cu(III) intermediates are invoked in some mechanisms. Organic cuprates often have the idealized formulas uR2sup>− and uR3sup>2−, where R is an alkyl or aryl. These reagents find use as nucleophilic
alkylating reagent Alkylation is the transfer of an alkyl group from one molecule to another. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion, or a carbene (or their equivalents). Alkylating agents are reagents for effecting al ...
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See also

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Cuprate superconductor Cuprate superconductors are a family of high-temperature superconducting materials made of layers of copper oxides (CuO2) alternating with layers of other metal oxides, which act as charge reservoirs. At ambient pressure, cuprate superconductor ...
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High-temperature superconductivity High-temperature superconductors (abbreviated high-c or HTS) are defined as materials that behave as superconductors at temperatures above , the boiling point of liquid nitrogen. The adjective "high temperature" is only in respect to previou ...
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Gilman reagent A Gilman reagent is a lithium and copper ( diorganocopper) reagent compound, R2CuLi, where R is an alkyl or aryl. These reagents are useful because, unlike related Grignard reagents and organolithium reagents, they react with organic halides to ...


References

{{Copper compounds Copper compounds Anions Oxometallates Transition metal oxyanions