Copper(I) bromide
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| Copper(I) bromide | |
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-bromide-sample.jpg/200px-Copper(I)-bromide-sample.jpg) |
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| Other names | cuprous bromide |
| Identifiers | |
| CAS number | [7787-70-4] |
| Properties | |
| Molecular formula | CuBr |
| Molar mass | 143.45 g/mol |
| Appearance | green powder |
| Density | 4.71 g/cm3, solid |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references |
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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.
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[edit] Preparation, basic properties, structure
The pure solid is colourless, although samples are often colored due to the presence of copper(II) impurities (see picture).[1] It is commonly prepared by the reduction of cupric salts with sulfite in the presence of bromide:[2]
Alternatively, and analogous to the synthesis of copper(I) chloride, it can be generated by dissolving copper powder in hydrobromic acid:
- 2 HBr + 2 Cu → 2 CuBr + H2
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.
[edit] Applications in organic chemistry
In the Sandmeyer reaction, CuBr is employed to convert anilines into the corresponding aryl bromides:[4]
- 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).
[edit] References
- ^ Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
- ^ Keller, R. N.; Wycoff, H. D. "Copper(I) chloride" Inorganic Syntheses 1946; Volume II, p 1-4.
- ^ 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
- ^ Hartwell, J. L. "o-Chlorobromobenzene" Organic Syntheses, Collected Volume 3, p.185 (1955).http://www.orgsyn.org/orgsyn/pdfs/CV3P0185.pdf
[edit] External links
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