Chromium(II) bromide

Chromium(II) bromide is the inorganic compound with the chemical formula CrBr₂. Like many metal dihalides, CrBr₂ adopts the "cadmium iodide structure" motif, i.e., it features sheets of octahedral Cr(II) centers interconnected by bridging bromide ligands. It is a white solid that dissolves in water to give blue solutions that are readily oxidized by air.

Chromium(II) bromide

Names
IUPAC name Chromium(II) bromide
Other names Chromium dibromide, Chromium bromide, Chromous bromide
Identifiers
CAS Number	10049-25-9 Y
3D model (JSmol)	Interactive image
ChemSpider	9249842
PubChem CID	21908600
UNII	6S9M6JI7W3 Y
CompTox Dashboard (EPA)	DTXSID90619903
InChI InChI=1S/2BrH.Cr/h2*1H;/q;;+2/p-2 Key: XZQOHYZUWTWZBL-UHFFFAOYSA-L
SMILES [Cr+2].[Br-].[Br-]
Properties
Chemical formula	CrBr2
Molar mass	211.804 g·mol−1
Appearance	White solid[1]
Density	4.236 g/cm3[1]
Melting point	842 °C (1,548 °F; 1,115 K)[1]
Solubility in water	soluble, exothermal blue solution[1]
Structure
Crystal structure	monoclinic[1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Synthesis and reactions

It can be prepared by reduction of chromium(III) bromide with hydrogen gas for 6–10 hours at 350-400 °C, cogenerating hydrogen bromide:^[2]

2 CrBr₃ + H₂ → 2 CrBr₂ + 2 HBr

Treatment of chromium powder with concentrated hydrobromic acid gives a blue hydrated chromium(II) bromide, which can be converted to a related acetonitrile complex.^[3]

Cr + n H₂O + 2 HBr → CrBr₂(H₂O)_n + H₂