Copper(I) bromide

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Copper(I) bromide
Sample of copper(I) bromide
Structure of CuBr
Identifiers
CAS number 7787-70-4 YesY
PubChem 24593
ChemSpider 22995 YesY
Jmol-3D images Image 1
Properties
Molecular formula CuBr
Molar mass 143.45 g/mol
Appearance green 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 slightly soluble
Solubility soluble in HCl, HBr, ammonium hydroxide
negligible in acetone, sulfuric acid
Refractive index (nD) 2.116
Dipole moment 1.46 D
Hazards
EU Index Not listed
Flash point Non-flammable
Related compounds
Other anions Copper(I) chloride
Copper(I) iodide
Other cations Silver(I) bromide
Copper(II) bromide
Mercury(I) bromide
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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Infobox references

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.

Preparation, basic properties, structure[edit]

The pure solid is colourless, although samples are often colored due to the presence of copper(II) impurities (see picture).[1] 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.[2] 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:[3]

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.

Applications in organic chemistry[edit]

In the Sandmeyer reaction, CuBr is employed to convert diazonium salts into the corresponding aryl bromides:[2]

ArN2+ + CuBr → ArBr + N2 + Cu+

The aforementioned complex CuBr(S(CH3)2) is widely used to generate organocopper reagents.[3] Related CuBr complexes are catalysts for Atom Transfer Radical Polymerization and Cu-catalyzed Cross-Dehydrogenative Couplings (CDC).

References[edit]

  1. ^ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
  2. ^ a b This report gives a procedure for generating CuBr: Jonathan L. Hartwell (1955), "o-Chlorobromobenzene", Org. Synth. ; Coll. Vol. 3: 185 .
  3. ^ a b 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

External links[edit]