Tungsten(V) bromide is the

inorganic compound An inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds⁠that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemistry''. Inorgan ...

with the

empirical formula In chemistry, the empirical formula of a chemical compound is the simplest whole number ratio of atoms present in a compound. A simple example of this concept is that the empirical formula of sulfur monoxide, or SO, is simply SO, as is the empir ...

W Br₅. The compound consists of bioctahedral structure, with two bridging bromide ligands, so its

molecular formula A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as paren ...

is W₂Br₁₀.

Preparation and structure

Tungsten(V) bromide is prepared by treating tungsten powder with

bromine Bromine is a chemical element; it has chemical symbol, symbol Br and atomic number 35. It is a volatile red-brown liquid at room temperature that evaporates readily to form a similarly coloured vapour. Its properties are intermediate between th ...

in the temperature range 650-1000 °C. The product is often contaminated with tungsten hexabromide. According to X-ray diffraction, the structure for tungsten pentabromide consists of an edge-shared bioctahedron.Y.-Q. Zheng, K. Peters and H. G. von Schnering (1998) "Crystal structure of tungsten pentabromide, WBr₅" '' Zeitschrift für Kristallographie - New Crystal Structures'' 213(3) 471

Reactions

Tungsten(V) bromide is the precursor to other tungsten compounds by reduction reactions. For example, tungsten(IV) bromide can be prepared by reduction with aluminium or tungsten.R.E. McCarley, T.M. Brown "The Preparation and Reactions of Some Tungsten (II) and Tungsten (IV) Halides" '' Inorg. Chem.'' 1964, volume 3, 1232-1236. The WBr₄ can be purified by

chemical vapor transport In chemistry, a chemical transport reaction describes a process for purification and crystallization of non-volatility (chemistry), volatile solids. The process is also responsible for certain aspects of mineral growth from the effluent of volca ...

. :3 WBr₅ + Al → 3 WBr₄ + AlBr₃ Excess tungsten pentabromide and aluminum tribromide are then removed by sublimation at 240 °C. Tungsten(II) bromide can then be obtained heating the tetrabromide. At 450-500 °C, gaseous pentabromide is evolved leaving yellow-green residue of WBr₂. An analogous method can also be applied to the synthesis of tungsten(II) chloride.

Reductive substitution reactions

Because it is relatively easy to reduce tungsten pentahalides, they can be used as alternative synthetic routes to tungsten (IV) halide adducts. For example, reaction of WBr₅ with

pyridine Pyridine is a basic (chemistry), basic heterocyclic compound, heterocyclic organic compound with the chemical formula . It is structurally related to benzene, with one methine group replaced by a nitrogen atom . It is a highly flammable, weak ...

gives WBr₄(py)₂. :2 WBr₅ + 7 C₅H₅N → 2 WBr₄(C₅H₅N)₂ + bipyridine + C₅H₅NHBr

References

{{bromides Bromides Tungsten halides Tungsten(V) compounds