Vanadium(III) bromide

Vanadium(III) bromide, also known as vanadium tribromide, describes the inorganic compounds with the formula VBr₃ and its hydrates. The anhydrous material is a green-black solid. In terms of its structure, the compound is polymeric with octahedral vanadium(III) surrounded by six bromide ligands.

Vanadium(III) bromide

Vanadium(III) bromide
Names
IUPAC name Vanadium(III) bromide
Other names Vanadium tribromide
Identifiers
CAS Number	13470-26-3 Y
3D model (JSmol)	Interactive image
ChemSpider	11476059 Y
ECHA InfoCard	100.033.382
EC Number	236-736-6
PubChem CID	83509
RTECS number	YW2750000
CompTox Dashboard (EPA)	DTXSID4065498
InChI InChI=1S/3BrH.V/h3*1H;/q;;;+3/p-3 Y Key: ZOYIPGHJSALYPY-UHFFFAOYSA-K Y InChI=1/3BrH.V/h3*1H;/q;;;+3/p-3 Key: ZOYIPGHJSALYPY-DFZHHIFOAP
SMILES Br[V](Br)Br
Properties
Chemical formula	VBr3
Molar mass	290.654 g/mol
Appearance	Green-black solid
Density	4 g/cm3
Solubility in water	soluble
Solubility	soluble in THF (forms adduct)
Magnetic susceptibility (χ)	+2890.0·10−6 cm3/mol
Structure
Coordination geometry	octahedral
Related compounds
Other anions	Vanadium(III) chloride
Other cations	Titanium(III) bromide Molybdenum(III) bromide
Related compounds	Vanadium(II) bromide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Preparation

VBr₃ has been prepared by treatment of vanadium tetrachloride with hydrogen bromide:

2 VCl₄ + 8 HBr → 2 VBr₃ + 8 HCl + Br₂

The reaction proceeds via the unstable vanadium(IV) bromide (VBr₄), which releases Br₂ near room temperature.^[1]

It is also possible to prepare vanadium(III) bromide by reacting bromine with vanadium or ferrovanadine:^[2]

2 V + 3 Br₂ → 2 VBr₃

2 VFe + 6 Br₂ → 2 VBr₃ + FeBr₃

Properties

Physical

Vanadium(III) bromide is present in the form of black, leafy, very hygroscopic crystals with a sometimes greenish sheen. It is soluble in water with green color. Its crystal structure is isotypic to that of vanadium(III) chloride with space group R3c (space group no. 167), a = 6.400 Å, c = 18.53 Å. When heated to temperatures of around 500 °C, a violet gas phase is formed, from which, under suitable conditions, red vanadium(IV) bromide can be separated by rapid cooling, which decomposes at −23 °C.^[2]

Chemical

Like vanadium(III) chloride, vanadium(III) bromide forms red-brown soluble complexes with dimethoxyethane and THF, such as mer-VBr₃(THF)₃.^[3]

Aqueous solutions prepared from VBr₃ contain the cation trans-[VBr₂(H₂O)₄]⁺. Evaporation of these solutions give the salt trans-[VBr₂(H₂O)₄]Br^.(H₂O)₂.^[4]

Further reading

• Stebler, A.; Leuenberger, B.; Guedel, H. U. "Synthesis and crystal growth of A₃M₂X₉ (A = Cs, Rb; M = Ti, V, Cr; X = Cl, Br)" Inorganic Syntheses (1989), volume 26, pages 377–85.