TetrachlorocuprateII

Tetrachlorocuprate(II) is an inorganic complex anion with the chemical formula [CuCl4]2-. It is a coordination complex where a central copper(II) ion is surrounded by four chloride ligands. The copper ion is in the +2 oxidation state. This anion is typically found in salts, such as potassium tetrachlorocuprate(II), K2[CuCl4]. These salts often exhibit characteristic colors, with many tetrachlorocuprate(II) compounds being blue or green.

The structure of the tetrachlorocuprate(II) anion is typically a distorted square planar geometry. This distortion arises from the Jahn-Teller effect, which is common for copper(II) complexes with octahedral or pseudo-octahedral coordination. In the solid state, the coordination environment around the copper ion might be further complicated by interactions with counterions or solvent molecules, leading to a more elongated or compressed octahedral geometry.

Tetrachlorocuprate(II) salts are soluble in water and some polar organic solvents. Solutions containing the tetrachlorocuprate(II) anion are often intensely colored, making them useful in qualitative analysis for the presence of copper. The stability of the anion is dependent on the concentration of chloride ions in solution. In dilute solutions, the chloride ligands can dissociate, leading to the formation of other copper complexes, such as [CuCl3]- or aqua complexes of copper(II). The formation of tetrachlorocuprate(II) is favored in concentrated chloride solutions.