tetrachloridocuprateII

Tetrachloridocuprate(II) is an inorganic chemical compound with the chemical formula [CuCl4]2-. It is an anionic complex where a central copper(II) ion is coordinated to four chloride ligands. The geometry of this complex is typically square planar, although tetrahedral distortions can occur. In aqueous solutions, the tetrachloridocuprate(II) ion is often found in equilibrium with other copper chloride complexes, such as the tetrachlorocuprate(II) ion, [CuCl3(H2O)]-, and dichlorocuprate(II), [CuCl2].

The compound is typically formed when copper(II) salts are dissolved in concentrated hydrochloric acid. The high concentration of chloride ions favors the formation of the tetrachloridocuprate(II) complex over aqua complexes. This complex is responsible for the characteristic deep green or blue-green color observed in solutions of copper(II) in concentrated chloride media. The color arises from d-d electronic transitions within the copper(II) ion, influenced by the ligand field provided by the chloride ions.

Tetrachloridocuprate(II) salts, such as potassium tetrachloridocuprate(II) (K2[CuCl4]), are known. These salts are often soluble in water and alcohols. The stability of the tetrachloridocuprate(II) ion is dependent on the concentration of chloride ions. In dilute solutions, it tends to dissociate or convert to less chlorinated copper complexes. The compound has found some limited use in analytical chemistry and as a precursor in the synthesis of other copper-containing materials.