Tungsten hexabromide
Chemical compound
From Wikipedia, the free encyclopedia
Tungsten hexabromide, also known as tungsten(VI) bromide, is a chemical compound of tungsten and bromine with the formula WBr6. It is an air-sensitive dark grey powder that decomposes above 200 °C to tungsten(V) bromide and bromine.[1][3]
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| Names | |
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IUPAC name
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| Other names
Hexabromotungsten | |
| Identifiers | |
3D model (JSmol) |
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| ChemSpider | |
PubChem CID |
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CompTox Dashboard (EPA) |
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| Properties | |
| WBr6 | |
| Molar mass | 663.264 g/mol |
| Appearance | Dark grey solid |
| Density | 5.32 g/cm3 |
| Melting point | 232 °C (450 °F; 505 K) (decomposition) |
| Hydrolysis | |
| Solubility | Soluble in ethanol, ether, carbon disulfide, and ammonia[1] |
| Structure[2] | |
| Rhombohedral | |
| R3 | |
a = 6.39 Å, c = 17.53 Å | |
Lattice volume (V) |
620.8 Å3 |
Formula units (Z) |
3 |
| Related compounds | |
Other anions |
Tungsten hexafluoride Tungsten hexachloride |
Related compounds |
Tungsten(V) bromide |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Production and reactions
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Tungsten hexabromide is mainly produced by the reaction of metallic tungsten and bromine at temperatures around 100 °C in a nitrogen atmosphere:[1][2]
- W + 3 Br2 → WBr6
Another method of producing this compound is by the reaction of tungsten hexacarbonyl and bromine at room temperature, releasing carbon monoxide.[4] It can also be produced by the metathesis reaction of boron tribromide and tungsten hexachloride.[5]
WBr6 is reduced with elemental antimony at elevated temperatures, consecutively producing, WBr5, WBr4, W4Br10, W5Br12, then finally WBr2 at 350 °C. This reaction produces antimony tribromide as a side product.[4][6] Any of these bromides can be reverted to the hexabromide by oxidation with bromine at 160 °C.[7]
Tungsten hexabromide is hydrolyzed in water, producing tungsten pentoxide and releasing bromine.[1]
Tungsten(VI) oxytetrabromide is produced by the reaction of tungsten hexabromide and tungsten(VI) oxide:[7]
- 2 WBr6 + WO3 → 3 WOBr4
Structure
The trigonal crystal structure of WBr6 consists of isolated WBr6 octahedra and is isostructural with α-WCl6.[2]