Copper(II) fluoride or cupric fluoride is an inorganic compound with the chemical formula CuF<sub>2</sub>. The anhydrous form is a white, ionic, crystalline, hygroscopic salt with a distorted rutile-type crystal structure, similar to other fluorides of chemical formulae MF<sub>2</sub> (where M is a metal). The dihydrate, , is blue in colour.
Copper(II) fluoride is slightly soluble in water, but starts to decompose in hot water, producing basic F<sup>âÂÂ</sup> and Cu(OH)<sup>+</sup> ions.
Copper(II) fluoride has a monoclinic crystal structure and cannot achieve a higher-symmetry structure. It forms rectangular prisms with a parallelogram base. Each copper ion has four neighbouring fluoride ions at 1.93 àseparation and two further away at 2.27 à. This distorted octahedral [4+2] coordination is a consequence of the JahnâÂÂTeller effect in d<sup>9</sup> copper(II), and leads to a distorted rutile structure similar to that of chromium(II) fluoride, , which is a d<sup>4</sup> compound.
Copper(II) fluoride can be synthesized from copper and fluorine at elevated temperatures. At a 53% conversion is achieved.
Cupric fluoride catalyzes the decomposition of nitric oxides in emission control systems.
Copper(II) fluoride can be used to make fluorinated aromatic hydrocarbons by reacting with aromatic hydrocarbons in an oxygen-containing atmosphere at temperatures above 450 ðC (842 ðF). This reaction is simpler than the Sandmeyer reaction, but is only effective in making compounds that can survive at the temperature used. A coupled reaction using oxygen and 2 HF regenerates the copper(II) fluoride, producing water. This method has been proposed as a "greener" method of producing fluoroaromatics since it avoids producing toxic waste products such as ammonium fluoride.
It loses fluorine in the molten stage at temperatures above 950 ðC (1742 ðF).
The complex anions CuF<sub>3</sub><sup>âÂÂ</sup>, CuF<sub>4</sub><sup>2âÂÂ</sup> and CuF<sub>6</sub><sup>4âÂÂ</sup> are formed if CuF<sub>2</sub> is exposed to substances containing fluoride ions F<sup>âÂÂ</sup>.