Tungsten bromide is the inorganic compound

Inorganic compound

Inorganic compounds have traditionally been considered to be of inanimate, non-biological origin. In contrast, organic compounds have an explicit biological origin. However, over the past century, the classification of inorganic vs organic compounds has become less important to scientists,...

 with the formula (W

Tungsten

Tungsten , also known as wolfram , is a chemical element with the chemical symbol W and atomic number 74.A hard, rare metal under standard conditions when uncombined, tungsten is found naturally on Earth only in chemical compounds. It was identified as a new element in 1781, and first isolated as...

Br₅

Bromine

Bromine ") is a chemical element with the symbol Br, an atomic number of 35, and an atomic mass of 79.904. It is in the halogen element group. The element was isolated independently by two chemists, Carl Jacob Löwig and Antoine Jerome Balard, in 1825–1826...

). The compound consists of bioctahedral structure, with two bridging bromide ligands.

Preparation and structure

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

Reactions

Tungsten(V) bromide is the precursor to a other tungsten compounds by reduction reactions. For example, tungsten(IV) bromide can be prepared by reduction with aluminium or tungsten. The WBr₄ can be purified by chemical vapor transport.

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

Pyridine is a basic heterocyclic organic compound with the chemical formula C5H5N. It is structurally related to benzene, with one C-H group replaced by a nitrogen atom...

gives WBr₄(py)₂.

2 WBr₅ + 7 C₅H₅N → 2 WBr₄(C₅H₅N)₂ + bipyridine + C₅H₅NHBr