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 pink ...

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 An oxide () is a chemical compound that contains at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion of oxygen, an O2– (molecular) ion. with oxygen in the oxidation state of −2. Most of the E ...

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. M ...

es, and anionic organocopper compounds.

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

hypochlorite In chemistry, hypochlorite is an anion with the chemical formula ClO−. It combines with a number of cations to form hypochlorite salts. Common examples include sodium hypochlorite (household bleach) and calcium hypochlorite (a component of ...

s 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 Copper(II) hydroxide is the hydroxide of copper with the chemical formula of Cu(OH)2. It is a pale greenish blue or bluish green solid. Some forms of copper(II) hydroxide are sold as "stabilized" copper(II) hydroxide, although they likely consi ...

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

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 ...

Organic cuprates

Lithium-diphenylcuprate-etherate-dimer-from-xtal-2D-skeletal

Cuprates have a role in

organic synthesis Organic synthesis is a special branch of chemical synthesis and is concerned with the intentional construction of organic compounds. Organic molecules are often more complex than inorganic compounds, and their synthesis has developed into one o ...

. 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 ...

References

{{Copper compounds Copper compounds Anions Oxometallates Transition metal oxyanions