Cuprate
Cuprate loosely refers to a material that can be viewed as containing anionic copper complexes. Examples include tetrachloridocuprate ([CuCl]), the superconductor YBaCuO, and the organocuprates (e.g., dimethylcuprate [Cu(CH)]). The term cuprates derives from the Latin word for copper, "cuprum". The term is mainly used in three contexts: oxide materials, anionic coordination complexes, and anionic organocopper compounds. Oxides. One of the simplest oxide-based cuprates is the copper(III) oxide KCuO. This species can be viewed as the K salt of the polyanion . 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: Coordination complexes. Copper forms many anionic coordination complexes 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 d configuration. Structures range from linear 2-coordinate, trigonal planar, and tetrahedral. Examples include dichloro and trichlorocuprates, i.e., linear [CuCl] and trigonal planar [CuCl]. Cyanide gives analogous complexes but also the trianionic tetracyanocuprate(I), [Cu(CN)]. Dicyanocuprate(I) exists in both molecular or polymeric motifs, depending on the countercation. Copper(II). The chlorocuprates include trichlorocuprate(II) [CuCl], which is dimeric, square-planar  tetrachlorocuprate(II) [CuCl], and pentachlorocuprate(II) [CuCl]. 3-Coordinate chlorocuprate(II) complexes are rare. Tetrachlorocuprate(II) complexes tend to adopt flattened tetrahedral geometry with orange colors. Sodium tetrahydroxycuprate (Na[Cu(OH)]) is an example of a homoleptic (all ligands being the same) hydroxide complex. Copper(III) and copper(IV). Hexafluorocuprate(III) [CuF] and hexafluorocuprate(IV) [CuF] are rare examples of copper(III) and copper(IV) complexes. They are strong oxidizing agents. 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 [CuR] and [CuR], where R is an alkyl or aryl . These reagents find use as nucleophilic alkylating reagents.