Tungsten hexabromide

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]

Tungsten hexabromide

Names
IUPAC name Tungsten(VI) bromide Tungsten hexabromide
Other names Hexabromotungsten
Identifiers
CAS Number	13701-86-5 Y
3D model (JSmol)	Interactive image
ChemSpider	103871330
PubChem CID	14440251
CompTox Dashboard (EPA)	DTXSID101294742
InChI Key: OQVJXQJWYQNWTI-UHFFFAOYSA-H InChI=1S/6BrH.W/h6*1H;/q;;;;;;+6/p-6
SMILES Br[W](Br)(Br)(Br)(Br)Br
Properties
Chemical formula	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)
Solubility in water	Hydrolysis
Solubility	Soluble in ethanol, ether, carbon disulfide, and ammonia[1]
Structure[2]
Crystal structure	Rhombohedral
Space group	R3
Lattice constant	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). Infobox references

Production and reactions

Production of WBr₆ by the reaction of W(CO)₆ and Br₂

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]