3D model (JSmol)
|Molar mass||95.611 g/mol|
|Appearance||black powder or lumps|
|Melting point||above 500 °C (932 °F; 773 K) (decomposes)|
|0.000033 g/100 mL (18 °C)|
Solubility product (Ksp)
|6 x 10−37|
|Solubility||soluble in HNO3, NH4OH, KCN |
insoluble in HCl, H2SO4
Refractive index (nD)
|US health exposure limits (NIOSH):|
|TWA 1 mg/m3 (as Cu)|
|TWA 1 mg/m3 (as Cu)|
IDLH (Immediate danger)
|TWA 100 mg/m3 (as Cu)|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|what is ?)(|
Copper monosulfide 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 a number of binary compounds of copper and sulfur (see copper sulfide for an overview of this subject), and has attracted interest because of its potential uses in catalysis and photovoltaics.
Alternatively, it can be prepared by melting an excess of sulfur with copper(I) sulfide or by precipitation with hydrogen sulfide from a solution of anhydrous copper(II) chloride in anhydrous ethanol.
CuS structure and bonding
Copper sulfide crystallizes in the hexagonal crystal system, and this is the form of the mineral covellite. There is also an amorphous high pressure form  which on the basis of the Raman spectrum has been described as having a distorted covellite structure. An amorphous room temperature semiconducting form produced by the reaction of a Cu(II) ethylenediamine complex with thiourea has been reported, which transforms to the crystalline covellite form at 30 °C.
The crystal structure of covellite has been reported several times, and whilst these studies are in general agreement on assigning the space group P63/mmc there are small discrepancies in bond lengths and angles between them. The structure was described as "extraordinary" by Wells and is quite different from copper(II) oxide, but similar to CuSe (klockmannite). The covellite unit cell contains 6 formula units (12 atoms) in which:
- 4 Cu atoms have tetrahedral coordination (see illustration).
- 2 Cu atoms have trigonal planar coordination (see illustration).
- 2 pairs of S atoms are only 207.1 pm apart  indicating the existence of an S-S bond (a disulfide unit).
- the 2 remaining S atoms form trigonal planar triangles around the copper atoms, and are surrounded by five Cu atoms in a pentagonal bipyramid (see illustration).
- The S atoms at each end of a disulfide unit are tetrahedrally coordinated to 3 tetrahedrally coordinated Cu atoms and the other S atom in the disulfide unit (see illustration).
The formulation of copper sulfide as CuIIS (i.e. containing no sulfur-sulfur bond) is clearly incompatible with the crystal structure, and also at variance with the observed diamagnetism as a Cu(II) compound would have a d9 configuration and be expected to be paramagnetic.
Studies using XPS indicate that all of the copper atoms have an oxidation state of +1. This contradicts a formulation based on the crystal structure and obeying the octet rule that is found in many textbooks (e.g.) describing CuS as containing both CuI and CuII i.e. (Cu+)2Cu2+(S2)2−S2−. An alternative formulation as (Cu+)3(S2−)(S2)− was proposed and supported by calculations. The formulation should not be interpreted as containing radical anion, but rather that there is a delocalized valence "hole". Electron paramagnetic resonance studies on the precipitation of Cu(II) salts indicates that the reduction of Cu(II) to Cu(I) occurs in solution.
the crystal structure of covellite
coordination of copper
coordination of copper
coordination of sulfur
coordination of sulfur-note disulfide unit
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