For cuprate superconductors, see Cuprate superconductor.

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.[citation needed]

Organic cuprates typically have a [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.[citation needed] An example of an organic cuprate is dimethylcuprate(I) anion [Cu(CH3)2]-.

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

Cuprate oxide salts are layered materials with general formula XYCu_{m}O_{n}, and some are non-stoichiometric. Many of these compounds are known for their superconducting properties.[citation needed]

Oxide cuprates

Many stable or metastable alkali metal cuprates(III) are known, all salts of the polyanion [CuO2−]_{n}. They are strong oxidants, oxidizing water.[1] They are typically produced through extremely large oxygen activities. Alkali metals larger than sodium produce dark-blue salts,[2][3] but sodium cuprate(III) is red-brown.[1]

One of the simplest oxide-based cuprates is potassium cuprate(III) KCuO2.[2] Even so, KCuO2 is a non-stoichiometric compound, so the more exact formula is 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.[3]

One of the most studied inorganic cuprates is YBa2Cu3O7, 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.[citation needed]

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 § 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 [CuCl2]− and trigonal planar [CuCl3](2−).[4] Cyanide gives analogous complexes but also the trianionic tetracyanocuprate(I), [Cu(CN)4](3−).[5] Dicyanocuprate(I), [Cu(CN)2]−, exists in both molecular or polymeric motifs, depending on the countercation.[6]

Copper(II)

Cuprates containing copper(II) include trichlorocuprate(II), [CuCl3]−, which is dimeric, and square-planar tetrachlorocuprate(II), [CuCl4](2−), and pentachlorocuprate(II), [CuCl5](3−).[7][8] 3-Coordinate chlorocuprate(II) complexes are rare.[9]

Tetrachlorocuprate(II) complexes tend to adopt flattened tetrahedral geometry with orange colors.[10][11][12][13]

Sodium tetrahydroxycuprate(II) (Na2[Cu(OH)4]) is an example of a homoleptic (all ligands being the same) hydroxide complex.[14]

Cu(OH)2 + 2 NaOH → Na2[Cu(OH)4]

Copper(III) and copper(IV)

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

Organic cuprates

Main article: 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 [CuR2]− and [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.[15]

See also

References

  1. ^ Magee, J. S. & Wood, R. H. (1965). "Studies of Sodium Cuprate(III) Stability". Canadian Journal of Chemistry. 43 (5): 1234–1237. doi:10.1139/v65-164
  2. ^ G. Brauer (ed.) (1963). "Potassium Cuprate (III)". Handbook of Preparative Inorganic Chemistry. Vol. 2. 2nd ed. NY: Academic Press. p. 1015.
  3. ^ Costa, Giorgio A. & Kaiser, Elena (1995). "Structural and thermal properties of the alkaline cuprate KCuO2". Thermochimica Acta. 269-270: 591–598. doi:10.1016/0040-6031(95)02575-8. Retrieved 20 January 2023.
  4. ^ Stricker, Marion; Linder, Thomas; Oelkers, Benjamin; Sundermeyer, Jörg (2010). "Cu(I)/(II) based catalytic ionic liquids, their metallo-laminate solid state structures and catalytic activities in oxidative methanol carbonylation". Green Chemistry. 12 (9): 1589. doi:10.1039/c003948a
  5. ^ Kroeker, Scott & Wasylishen, Roderick E. (1999). "A multinuclear magnetic resonance study of crystalline tripotassium tetracyanocuprate". Canadian Journal of Chemistry. 77 (11): 1962–1972. doi:10.1139/v99-181
  6. ^ Bowmaker, Graham A.; Hartl, Hans; Urban, Victoria (2000). "Crystal Structures and Vibrational Spectroscopy of [NBu4][Cu(CN)X] (X = Br, I) and [NBu4][Cu3(CN)4]·CH3CN". Inorganic Chemistry. 39 (20): 4548–4554. doi:10.1021/ic000399s
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  8. ^ Willett, Roger D.; Butcher, Robert E.; Landee, Christopher P.; Twamley, Brendan (2006). "Two Halide Exchange in Copper(II) Halide Dimers: (4,4′-Bipyridinium)Cu2Cl6−x BRX". Polyhedron. 25 (10): 2093–2100. doi:10.1016/j.poly.2006.01.005
  9. ^ Hasselgren, Catrin; Jagner, Susan; Dance, Ian (2002). "Three-Coordinate [CuIIX3]− (X = Cl, Br), Trapped in a Molecular Crystal". Chemistry – A European Journal. 8 (6): 1269–1278. doi:10.1002/1521-3765(20020315)8:6<1269::AID-CHEM1269>3.0.CO;2-9. PMID 11921210
  10. ^ Mahoui, A.; Lapasset, J.; Moret, J.; Saint Grégoire, P. (1996). "Tetraethylammonium Tetramethylammonium Tetrachlorocuprate(II), [(C2H5)4N][(CH3)4N][CuCl4]". Acta Crystallographica Section C. 52 (11): 2674–2676. doi:10.1107/S0108270196009031
  11. ^ Guillermo Mínguez Espallargas; Lee Brammer; Jacco van de Streek; Kenneth Shankland; Alastair J. Florence; Harry Adams (2006). "Reversible Extrusion and Uptake of HCl Molecules by Crystalline Solids Involving Coordination Bond Cleavage and Formation". J. Am. Chem. Soc.. 128 (30): 9584–9585. doi:10.1021/ja0625733. PMID 16866484
  12. ^ Kelley, A.; Nalla, S.; Bond, M. R. (2015). "The square-planar to flattened-tetrahedral CuX42− (X = Cl, Br) structural phase transition in 1,2,6-trimethylpyridinium salts". Acta Crystallogr. B. 71 (Pt 1): 48–60. doi:10.1107/S205252061402664X. PMID 25643715
  13. ^ Egon Wiberg; Nils Wiberg; Arnold Frederick Holleman (2001). Inorganic Chemistry. Academic Press. pp. 1252–1264. ISBN 0-12-352651-5.
  14. ^ Brauer, G. (ed.) (1963). "Sodium Tetrahydroxocuprate(II)". Handbook of Preparative Inorganic Chemistry. Vol. 1. 2nd ed. New York, NY: Academic Press. p. 1015.
  15. ^ Louis S. Hegedus (1999). Transition metals in the synthesis of complex organic molecules. University Science Books. pp. 61–65. ISBN 1-891389-04-1.