Cuprate

{{Short description|Metallic compound with anionic copper complexes}} {{for|cuprate superconductors|Cuprate superconductor}}

{{Use American English|date=January 2019}} {{Use mdy dates|date=January 2019}}

'''Cuprates''' are a class of compounds that contain copper (Cu) atom(s) in an anion. The term 'cuprate' itself originates from 'cuprum', the Latin word for copper. Cuprates appear mainly in three contexts: anionic organocopper species; inorganic, anionic coordination complexes; and complex oxides.{{cn|date=January 2024}}

Organic cuprates typically have a {{chem2|[CuR2]−}} formula, corresponding to a copper(I) oxidation state, where at least one of the R groups can be any organic group. These compounds are frequently used in organic synthesis as weak nucleophiles that preferentially attack π bonds.{{cn|date=January 2024}} An example of an organic cuprate is dimethylcuprate(I) anion {{chem2|[Cu(CH3)2]-}}.

Inorganic cuprate complexes have a wide variety of formulas. An inorganic cuprate example is the tetrachloridocuprate(II) or tetrachlorocuprate(II) ({{chem2|[CuCl4](2-)|auto=1}}) anion, a copper(II) atom coordinated to four chloride ions.

Cuprate oxide salts are layered materials with general formula {{chem2|XYCu_{''m''}O_{''n''}|}}, and some are non-stoichiometric. Many of these compounds are known for their superconducting properties.{{cn|date=January 2024}}

==Oxide cuprates== thumb|Potassium cuprate Many stable or metastable alkali metal cuprates(III) are known, all salts of the polyanion {{chem2|[CuO2−]_{''n''}|}}. They are strong oxidants, oxidizing water.<ref name="cjc" /> They are typically produced through extremely large oxygen activities. Alkali metals larger than sodium produce dark-blue salts,<ref name=BHandbk/><ref name="TA">{{cite journal |last1=Costa |first1=Giorgio A. |last2=Kaiser |first2=Elena |title=Structural and thermal properties of the alkaline cuprate KCuO₂ |journal=Thermochimica Acta |date=1995 |volume=269-270 |pages=591–598 |doi=10.1016/0040-6031(95)02575-8 |url=https://www.sciencedirect.com/science/article/abs/pii/0040603195025758 |access-date=20 January 2023|url-access=subscription }}</ref> but sodium cuprate(III) is red-brown.<ref name="cjc">{{cite journal |last1=Magee |first1=J. S. |last2=Wood |first2=R. H. |title=Studies of Sodium Cuprate(III) Stability |journal=Canadian Journal of Chemistry |date=1965 |volume=43 |issue=5 |pages=1234–1237 |doi=10.1139/v65-164 |doi-access=}}</ref>

One of the simplest oxide-based cuprates is potassium cuprate(III) {{chem2|KCuO2}}.<ref name=BHandbk>{{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=2|page=1015}}</ref> Even so, {{chem2|KCuO2}} is a non-stoichiometric compound, so the more exact formula is {{chem2|KCuO_{''x''}|}} 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" />

One of the most studied inorganic cuprates is {{chem2|YBa2Cu3O7|auto=1}}, also known as YBCO. This oxide cuprate has been the subject of extensive research due to its ability to conduct electricity without resistance at relatively high temperatures. It is the parent of a family of cuprate superconductors.{{cn|date=January 2024}}

==Coordination complexes== Copper forms many anionic coordination complexes with negatively charged ligands such as cyanide, hydroxide, and halides, as well as alkyls and aryls (see {{slink||Organic cuprates}}). ===Copper(I)=== 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 {{chem2|[CuCl2]−}} and trigonal planar {{chem2|[CuCl3](2−)}}.<ref>{{cite journal |doi=10.1039/c003948a |title=Cu(I)/(II) based catalytic ionic liquids, their metallo-laminate solid state structures and catalytic activities in oxidative methanol carbonylation |year=2010 |last1=Stricker |first1=Marion |last2=Linder |first2=Thomas |last3=Oelkers |first3=Benjamin |last4=Sundermeyer |first4=Jörg |journal=Green Chemistry |volume=12 |issue=9 |page=1589}}</ref> Cyanide gives analogous complexes but also the trianionic tetracyanocuprate(I), {{chem2|[Cu(CN)4](3−)}}.<ref>{{Cite journal |doi=10.1139/v99-181 |title=A multinuclear magnetic resonance study of crystalline tripotassium tetracyanocuprate |year=1999 |last1=Kroeker |first1=Scott |last2=Wasylishen |first2=Roderick E. |journal=Canadian Journal of Chemistry |volume=77 |issue=11 |pages=1962–1972}}</ref> Dicyanocuprate(I), {{chem2|[Cu(CN)2]−}}, exists in both molecular or polymeric motifs, depending on the countercation.<ref>{{cite journal |doi=10.1021/ic000399s |title=Crystal Structures and Vibrational Spectroscopy of [NBu₄][Cu(CN)X] (X = Br, I) and [NBu₄][Cu₃(CN)4]·CH₃CN |year=2000 |last1=Bowmaker |first1=Graham A. |last2=Hartl |first2=Hans |last3=Urban |first3=Victoria |journal=Inorganic Chemistry |volume=39 |issue=20 |pages=4548–4554}}</ref>

===Copper(II)=== thumb|upright|right|Caesium salt of hexafluorocuprate(IV) Cuprates containing copper(II) include trichlorocuprate(II), {{chem2|[CuCl3]−}}, which is dimeric, and square-planar tetrachlorocuprate(II), {{chem2|[CuCl4](2−)}}, and pentachlorocuprate(II), {{chem2|[CuCl5](3−)}}.<ref name="Greenwood&Earnshaw2nd">{{Greenwood&Earnshaw2nd}}</ref><ref>{{cite journal |doi=10.1016/j.poly.2006.01.005|title=Two Halide Exchange in Copper(II) Halide Dimers: (4,4{{prime}}-Bipyridinium)Cu₂Cl_6−''x'' ''BRX'' |year=2006 |last1=Willett |first1=Roger D. |last2=Butcher |first2=Robert E. |last3=Landee |first3=Christopher P. |last4=Twamley |first4=Brendan |journal=Polyhedron |volume=25 |issue=10 |pages=2093–2100}}</ref> 3-Coordinate chlorocuprate(II) complexes are rare.<ref>{{cite journal |doi=10.1002/1521-3765(20020315)8:6<1269::AID-CHEM1269>3.0.CO;2-9 |title=Three-Coordinate [Cu^IIX₃]⁻ (X = Cl, Br), Trapped in a Molecular Crystal |year=2002 |last1=Hasselgren |first1=Catrin |last2=Jagner |first2=Susan |last3=Dance |first3=Ian |journal=Chemistry – A European Journal |volume=8 |issue=6 |pages=1269–1278| pmid=11921210}}</ref>

Tetrachlorocuprate(II) complexes tend to adopt flattened tetrahedral geometry with orange colors.<ref>{{cite journal |doi=10.1107/S0108270196009031|title=Tetraethylammonium Tetramethylammonium Tetrachlorocuprate(II), [(C₂H₅)₄N][(CH₃)₄N][CuCl₄] |year=1996 |last1=Mahoui |first1=A. |last2=Lapasset |first2=J. |last3=Moret |first3=J. |last4=Saint Grégoire |first4=P. |journal=Acta Crystallographica Section C |volume=52 |issue=11 |pages=2674–2676}}</ref><ref>{{cite journal |title=Reversible Extrusion and Uptake of HCl Molecules by Crystalline Solids Involving Coordination Bond Cleavage and Formation |author1=Guillermo Mínguez Espallargas |author2=Lee Brammer |author3=Jacco van de Streek |author4=Kenneth Shankland |author5=Alastair J. Florence |author6=Harry Adams |journal=J. Am. Chem. Soc.| year=2006 |volume=128 |issue=30 |pages=9584–9585 |doi=10.1021/ja0625733 |pmid=16866484}}</ref><ref>{{cite journal |title=The square-planar to flattened-tetrahedral CuX₄²⁻ (''X'' = Cl, Br) structural phase transition in 1,2,6-trimethylpyridinium salts |first1=A. |last1=Kelley |first2=S. |last2=Nalla |first3=M. R. |last3=Bond |journal=Acta Crystallogr. B |year=2015 |volume=71 |issue=Pt 1 |pages=48–60 |doi=10.1107/S205252061402664X |pmid=25643715}}</ref><ref>{{cite book |url=https://books.google.com/books?id=vEwj1WZKThEC&pg=PA1264 |pages=1252–1264 |title=Inorganic Chemistry |author1=Egon Wiberg |author2=Nils Wiberg |author3=Arnold Frederick Holleman |publisher=Academic Press |year=2001 |isbn=0-12-352651-5}}</ref>

Sodium tetrahydroxycuprate(II) ({{chem2|Na2[Cu(OH)4]}}) is an example of a homoleptic (all ligands being the same) hydroxide complex.<ref>{{cite book|entry=Sodium Tetrahydroxocuprate(II) |title=Handbook of Preparative Inorganic Chemistry |edition=2nd |editor-first=G. |editor-last=Brauer |publisher=Academic Press |date=1963 |location=New York, NY |volume=1 |page=1015}}</ref> :{{chem2|Cu(OH)2 + 2 NaOH → Na2[Cu(OH)4]}}

===Copper(III) and copper(IV)=== Hexafluorocuprate(III) {{chem2|[CuF6](3−)}} and hexafluorocuprate(IV) {{chem2|[CuF6](2−)}} are rare examples of copper(III) and copper(IV) complexes. They are strong oxidizing agents.

==Organic cuprates== [[File:Lithium-diphenylcuprate-etherate-dimer-from-xtal-2D-skeletal.png|thumb|upright|Structure of lithium diphenylcuprate(I) etherate, {{chem2|2Ph2Cu]−Li+*2OEt2}}.<ref>{{cite journal|doi=10.1002/anie.199003001|title=Synthesis and Structure of a Dimeric Lithium Diphenylcuprate:[{Li(OEt₂)}(CuPh₂)]₂ |year=1990 |last1=Lorenzen |first1=Nis Peter |last2=Weiss |first2=Erwin |journal=Angewandte Chemie International Edition in English |volume=29 |issue=3 |pages=300}}</ref>]]

{{main|Organocopper compound}} 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 {{chem2|[CuR2]−}} and {{chem2|[CuR3](2−)}}, 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>{{cite book |url=https://books.google.com/books?id=101pNv3QpEIC&pg=PA61 |pages=61–65 |title=Transition metals in the synthesis of complex organic molecules |author=Louis S. Hegedus |publisher=University Science Books |year=1999 |isbn=1-891389-04-1}}</ref>

==See also== *Cuprate superconductor *High-temperature superconductivity *Gilman reagent ==References== {{reflist|30em}}

{{Copper compounds}}

Category:Copper compounds Category:Anions Category:Transition metal oxyanions Category:Oxometallates