Uranium pentabromide

Uranium pentabromide is an inorganic chemical compound with the formula U₂Br₁₀.

Uranium pentabromide

Identifiers
CAS Number	13775-16-1
3D model (JSmol)	Interactive image
ChemSpider	123110
PubChem CID	139592
CompTox Dashboard (EPA)	DTXSID40160298
InChI InChI=1S/5BrH.U/h5*1H;/q;;;;;+5/p-5 Key: UAGSJUTVOXEWHQ-UHFFFAOYSA-I
SMILES Br[U](Br)(Br)(Br)Br
Properties
Chemical formula	UBr5
Molar mass	637.549 g/mol
Appearance	dark brown, hygroscopic crystalline solid
Solubility in water	decomposes
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Synthesis

The compound is made by reacting the elements in an acetonitrile solvent, or by reacting bromine with uranium metal or uranium tetrabromide at 55 °C (131 °F; 328 K).^[1]

Properties

Uranium pentabromide is a hygroscopic dark brown solid that decomposes in water and most organic solvents, the exceptions being acetonitrile or dichloromethane.^[1] The compound is rather unstable and difficult to purify,^[2] decomposing at 80 °C (176 °F; 353 K) into its constituent elements.^[3] The crystal structure is the same as that of β-UCl₅, which is triclinic and consists of U₂Br₁₀ dimers.^[4]

Complexes

Stable complexes of the form UBr₅L are known with such ligands as triphenylphosphine oxide and hexamethylphosphoramide, and are obtained by brominating UBr₄ in the presence of the desired ligand.^[2] In addition, it is possible to obtain a hexabromouranate(V) salt by reacting UBr₅ with a monovalent bromide in thionyl bromide:^[1]

U₂Br₁₀ + 2MBr → 2M⁺[UBr₆]⁻