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Cuprates are a class of compounds that contain copper (Cu) atom(s) in an anion. They can be broadly categorized into two main types:
1. Inorganic cuprates: These compounds have a general formula of Template:Chem2. Some of them are non-stoichiometric. Many of these compounds are known for their superconducting properties.Template:Cn An example of an inorganic cuprate is the tetrachloridocuprate(II) or tetrachlorocuprate(II) (Template:Chem2), an anionic coordination complex that features a copper atom in an oxidation state of +2, surrounded by four chloride ions.
2. Organic cuprates: These are organocopper compounds, some of which having a general formula of Template:Chem2, where copper is in an oxidation state of +1, where at least one of the R groups can be any organic group. These compounds, characterized by copper bonded to organic groups, are frequently used in organic synthesis due to their reactivity.Template:Cn An example of an organic cuprate is dimethylcuprate(I) anion Template:Chem2.
One of the most studied cuprates is Template:Chem2, a high-temperature superconducting material. This oxide cuprate has been the subject of extensive research due to its ability to conduct electricity without resistance at relatively high temperatures.Template:Cn
The term 'cuprate' originates from 'cuprum', the Latin word for copper. It is primarily used in the context of oxide materials, anionic coordination complexes, and anionic organocopper compounds, reflecting the diverse roles of copper in chemistry. The term is mainly used in three contexts: oxide materials, anionic coordination complexes, and anionic organocopper compounds.Template:Cn
Oxide cupratesEdit
One of the simplest oxide-based cuprates is potassium cuprate(III) Template:Chem2. This species can be viewed as the Template:Chem2 salt of the polyanion Template:Chem2. As such the material is classified as an oxide cuprate. This dark blue diamagnetic solid is produced by heating potassium peroxide and copper(II) oxide in an atmosphere of oxygen:<ref>Template:Cite book</ref>
Other cuprates(III) of alkali metals are known; in addition, the structures of Template:Chem2 (caesium cuprate(III)) have been determined as well.<ref name="zaac2">Template:Cite journal</ref>
Template:Chem2 was discovered first in 1952 by V. K. Wahl and W. Klemm, they synthesized this compound by heating copper(II) oxide and potassium superoxide in an atmosphere of oxygen.<ref name="zaac">Template:Cite journal</ref>
It can also be synthesized by heating potassium superoxide and copper powder:<ref name="TA">Template:Cite journal</ref>
Template:Chem2 reacts with the air fairly slowly. It starts to decompose at Template:Cvt and its color changes from blue to pale green at Template:Cvt. Its melting point is Template:Cvt.<ref name="zaac" /><ref name="TA" />
Template:Chem2 (blue-black) and Template:Chem2 (black) can be prepared by reaction of rubidium oxide and caesium oxide with copper(II) oxide powders, at Template:Cvt and Template:Cvt in oxygen atmosphere, respectively. Either of them reacts with the air fast, unlike Template:Chem2.<ref name="TA" />
In fact, Template:Chem2 is a non-stoichiometric compound, so the more exact formula is Template:Chem2 and x is very close to 2. This causes the formation of defects in the crystal structure, and this leads to the tendency of this compound to be reduced. <ref name="TA" />
Sodium cuprate(III) Template:Chem2 can be produced by using hypochlorites or hypobromites to oxidize copper hydroxide under alkaline and low temperature conditions.<ref name="cjc">Template:Cite journal</ref>
Cuprates(III) are not stable in water, and they can oxidize water as well.<ref name="cjc" />
Sodium cuprate(III) is reddish-brown, but turns black gradually as it decomposes to copper(II) oxide.<ref name="cjc" /> In order to prevent decomposition, it must be prepared at low temperature in the absence of light.Template:Cn
Coordination complexesEdit
Copper forms many anionic coordination complexes with negatively charged ligands such as cyanide, hydroxide, and halides, as well as alkyls and aryls.
Copper(I)Edit
Cuprates containing copper(I) tend to be colorless, reflecting their d10 configuration. Structures range from linear 2-coordinate, trigonal planar, and tetrahedral molecular geometry. Examples include linear Template:Chem2 and trigonal planar Template:Chem2.<ref>Template:Cite journal</ref> Cyanide gives analogous complexes but also the trianionic tetracyanocuprate(I), Template:Chem2.<ref>Template:Cite journal</ref> Dicyanocuprate(I), Template:Chem2, exists in both molecular or polymeric motifs, depending on the countercation.<ref>Template:Cite journal</ref>
Copper(II)Edit
Cuprates containing copper(II) include trichlorocuprate(II), Template:Chem2, which is dimeric, and square-planar tetrachlorocuprate(II), Template:Chem2, and pentachlorocuprate(II), Template:Chem2.<ref name="Greenwood&Earnshaw2nd">Template:Greenwood&Earnshaw2nd</ref><ref>Template:Cite journal</ref> 3-Coordinate chlorocuprate(II) complexes are rare.<ref>Template:Cite journal</ref>
Tetrachlorocuprate(II) complexes tend to adopt flattened tetrahedral geometry with orange colors.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref><ref>Template:Cite journal</ref><ref>Template:Cite book</ref>
Sodium tetrahydroxycuprate(II) (Template:Chem2) is an example of a homoleptic (all ligands being the same) hydroxide complex.<ref>Template:Cite book</ref>
Copper(III) and copper(IV)Edit
Hexafluorocuprate(III) Template:Chem2 and hexafluorocuprate(IV) Template:Chem2 are rare examples of copper(III) and copper(IV) complexes. They are strong oxidizing agents.
Organic cupratesEdit
{{#invoke:Labelled list hatnote|labelledList|Main article|Main articles|Main page|Main pages}} Cuprates have a role in organic synthesis. They are invariably Cu(I), although Cu(II) or even Cu(III) intermediates are invoked in some chemical reactions. Organic cuprates often have the idealized formulas Template:Chem2 and Template:Chem2, both of which contain copper in an oxidation state of +1, where R is an alkyl or aryl. These reagents find use as nucleophilic alkylating reagents.<ref>Template:Cite book</ref>