Copper(I) bromide
Copper(I) bromide is the chemical compound with the formula CuBr. This diamagnetic solid adopts a polymeric structure akin to that for zinc sulfide. The compound is widely used in the synthesis of organic compounds and as a lasing medium in copper bromide lasers.
 | |
 | |
| Names | |
|---|---|
| Other names
Cuprous bromide | |
| Identifiers | |
3D model (JSmol) |
|
| ChemSpider | |
| ECHA InfoCard | 100.029.210 |
PubChem CID |
|
| UNII | |
CompTox Dashboard (EPA) |
|
| |
| |
| Properties | |
| CuBr | |
| Molar mass | 143.45 g/mol |
| Appearance | white powder (see text) |
| Density | 4.71 g/cm3, solid |
| Melting point | 492 °C (918 °F; 765 K) |
| Boiling point | 1,345 °C (2,453 °F; 1,618 K) |
| slightly soluble | |
| Solubility | soluble in HCl, HBr, ammonium hydroxide, acetonitrile negligible in acetone, sulfuric acid |
| -49.0·10−6 cm3/mol | |
Refractive index (nD) |
2.116 |
| 1.46 D | |
| Hazards | |
| Flash point | Non-flammable |
| NIOSH (US health exposure limits): | |
PEL (Permissible) |
TWA 1 mg/m3 (as Cu)[1] |
REL (Recommended) |
TWA 1 mg/m3 (as Cu)[1] |
IDLH (Immediate danger) |
TWA 100 mg/m3 (as Cu)[1] |
| Related compounds | |
Other anions |
Copper(I) chloride Copper(I) iodide |
Other cations |
Silver(I) bromide Copper(II) bromide Mercury(I) bromide |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
  | |
| Infobox references | |
Preparation, basic properties, structure
The compound is white, although samples are often colored due to the presence of copper(II) impurities.[2] The copper(I) ion also oxidizes easily in air. It is commonly prepared by the reduction of cupric salts with sulfite in the presence of bromide.[3] For example, the reduction of copper(II) bromide with sulfite yields copper(I) bromide and hydrogen bromide:
- 2 CuBr2 + H2O + SO32− → 2 CuBr + SO42− + 2 HBr
CuBr is insoluble in most solvents due to its polymeric structure, which features four-coordinated, tetrahedral Cu centers interconnected by bromide ligands (ZnS structure). Upon treatment with Lewis bases, CuBr converts to molecular adducts. For example, with dimethyl sulfide, the colorless complex is formed:[4]
- CuBr + S(CH3)2 → CuBr(S(CH3)2)
In this coordination complex, the copper is two-coordinate, with a linear geometry. Other soft ligands afford related complexes. For example, triphenylphosphine gives CuBr(P(C6H5)3), although this species has a more complex structure. Thermal excitation of copper(I) bromide vapour yields a blue violet emission which is of greater saturation than known copper(I) chloride emission.[5] Copper(I) bromide is hence an advantageous emitter in pyrotechnic flames.
Applications in organic chemistry
In the Sandmeyer reaction, CuBr is employed to convert diazonium salts into the corresponding aryl bromides:[3]
- ArN2+ + CuBr → ArBr + N2 + Cu+
The aforementioned complex CuBr(S(CH3)2) is widely used to generate organocopper reagents.[4] Related CuBr complexes are catalysts for atom transfer radical polymerization and Cu-catalyzed cross-dehydrogenative couplings (CDC).
References
- NIOSH Pocket Guide to Chemical Hazards. "#0150". National Institute for Occupational Safety and Health (NIOSH).
- Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
- This report gives a procedure for generating CuBr: Jonathan L. Hartwell (1955). "o-Chlorobromobenzene". Organic Syntheses.; Collective Volume, 3, p. 185.
- Jarowicki, K.; Kocienski, P. J.; Qun, L. "1,2-Metallate Rearrangement: (Z)-4-(2-Propenyl)-3-Octen-1-ol" Organic Syntheses, Collected Volume 10, p.662 (2004).http://www.orgsyn.org/orgsyn/pdfs/V79P0011.pdf
- E.-C. Koch, Spectral Investigation and Color Properties of Copper(I) Halides CuX (X=F, Cl, Br, I) in Pyrotechnic Combustion Flames, Propellants Explos. Pyrotech. 2015, 40, 798-802.
