Copper(II) sulfide

Copper(II) sulfide is a chemical compound of copper and sulfur. It occurs in nature as the dark indigo blue mineral covellite. It is a moderate conductor of electricity. A black colloidal precipitate of CuS is formed when hydrogen sulfide, H2S, is bubbled through solutions of Cu(II) salts. It is one of number of binary compounds of copper and sulfur (see copper sulfide). It has attracted interest because of its potential uses in catalysis and photovoltaics

Structure
The structure of CuS is unusual as it often formulated as CuI2CuIIS2 S containing copper in two different oxidation states (+1 and +2) along with sulfide,S2 &minus; and disulfide, S22 &minus;anions. In the crystal one third of the copper atoms have three near sulfur neighbors at the corners of a triangle and the remainder have four arranged tetrahedrally. . Calculations have shown that the mixed valence structure is less stable than one where the copper atoms have fractional oxidation states. Observations of the 63Cu NMR spectrum indicate two different types of copper atom present although the EPR spectrum is consistent with only one.