Copper(I) bromide

Copper(I) bromide
Names


Other names Cuprous bromide
Identifiers
CAS Number	7787-70-4^Y
3D model (JSmol)	Interactive image
ChemSpider	22995^Y
ECHA InfoCard	100.029.210
PubChem CID	24593
UNII	R8V209A5G0^Y
CompTox Dashboard (EPA)	DTXSID6052530
InChI InChI=1S/BrH.Cu/h1H;/q;+1/p-1^Y Key: NKNDPYCGAZPOFS-UHFFFAOYSA-M^Y InChI=1/BrH.Cu/h1H;/q;+1/p-1 Key: NKNDPYCGAZPOFS-REWHXWOFAY
SMILES Br[Cu]
Properties
Chemical formula	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)
Solubility in water	insoluble; slightly soluble in cold water
Solubility product (K_sp)	6.27×10⁻⁹^[1]
Solubility	soluble in HCl, HBr, ammonium hydroxide, acetonitrile negligible in acetone, sulfuric acid
Magnetic susceptibility (χ)	−49.0×10⁻⁶ cm³/mol
Refractive index (n_D)	2.116
Dipole moment	1.46 D
Hazards
Flash point	Non-flammable
NIOSH (US health exposure limits):
PEL (Permissible)	TWA 1 mg/m³ (as Cu)^[2]
REL (Recommended)	TWA 1 mg/m³ (as Cu)^[2]
IDLH (Immediate danger)	TWA 100 mg/m³ (as Cu)^[2]
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). Y verify (what is ^YN ?) Infobox references

Chemical compound

Copper(I) bromide is the chemical compound with the formula CuBr. This white 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.

Preparation, basic properties, structure

The compound is white, although samples are often colored due to the presence of copper(II) impurities.^[3] 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.^[4] For example, the reduction of copper(II) bromide with sulfite yields copper(I) bromide and hydrogen bromide:

2 CuBr₂ + H₂O + SO²⁻
₃ → 2 CuBr + SO²⁻
₄ + 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:^[5]

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.^[6] 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:^[4]

ArN⁺
₂ + CuBr → ArBr + N₂ + Cu⁺

The aforementioned complex CuBr(S(CH₃)₂) is widely used to generate organocopper reagents.^[5] Related CuBr complexes are catalysts for atom transfer radical polymerization and copper-catalyzed cross-dehydrogenative couplings (CDC).

References

^ Rumble, John (June 18, 2018). CRC Handbook of Chemistry and Physics (99th ed.). CRC Press. pp. 5–188. ISBN 978-1138561632.
^ ^a ^b ^c 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.
^ ^a ^b This report gives a procedure for generating CuBr: Hartwell, Jonathan L. (1955). "o-Chlorobromobenzene". Organic Syntheses; Collected Volumes, vol. 3, p. 185.
^ ^a ^b Jarowicki, K.; Kocienski, P. J.; Qun, L. "1,2-Metallate Rearrangement: (Z)-4-(2-Propenyl)-3-Octen-1-ol". Organic Syntheses. 79: 11; Collected Volumes, vol. 10, p. 662.
^ Koch, E.-C. (2015). "Spectral Investigation and Color Properties of Copper(I) Halides CuX (X=F, Cl, Br, I) in Pyrotechnic Combustion Flames". Propellants Explos. Pyrotech. 40 (6): 798–802. doi:10.1002/prep.201500231.