Chromium(III) bromide

Chromium(III) bromide
Names
	IUPAC name Chromium(III) bromide
	Other names Chromium tribromide, Chromium bromide, Chromic bromide
Identifiers
CAS Number	10031-25-1; 13478-06-3 (hexahydrate);
3D model (JSmol)	Interactive image;
ChemSpider	74280;
ECHA InfoCard	100.030.068
EC Number	233-088-6;
PubChem CID	82309;
UNII	WZB719DDER ;
CompTox Dashboard (EPA)	DTXSID40905343 ;
	InChI InChI=1S/3BrH.Cr/h3*1H;/q;;;+3/p-3 Key: UZDWIWGMKWZEPE-UHFFFAOYSA-K;
	SMILES [Cr+3].[Br-].[Br-].[Br-];
Properties
Chemical formula	CrBr3
Molar mass	291.71 g/mol
Appearance	Black lustrous crystals; green in transmitted light, reddish in reflected light[1]
Density	4.25 g/cm3[2]
Melting point	1,130 °C (2,070 °F; 1,400 K) (anhydrous)[2] ; 79 °C (hexahydrate)
Solubility in water	insoluble in cold water, soluble with addition of Chromium(II) ion salts,[1] soluble in hot water[2]
Structure
Crystal structure	trigonal
Hazards
	NIOSH (US health exposure limits):
PEL (Permissible)	TWA 1 mg/m3[3]
REL (Recommended)	TWA 0.5 mg/m3[3]
IDLH (Immediate danger)	250 mg/m3[3]
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
	Infobox references

Chromium(III) bromide is an inorganic compound with the chemical formula CrBr₃. It is a dark colored solid that appears green in transmitted light but red with reflected light. It is used as a precursor to catalysts for the oligomerization of ethylene.

Synthesis

The compound is prepared in a tube furnace by the reaction of bromine vapor and chromium powder at 1000 °C. It is purified by extracting with absolute diethyl ether to remove any CrBr₂, and is subsequently washed with absolute diethyl ether and absolute ethanol.[1]

Analogous to the behavior of related chromium(III) halides, the tribromide dissolves in water to give CrBr₃(H₂O)₃ only upon the addition of catalytic amounts of a reducing agent, which generates CrBr₂.[1] The reducing agent generates chromous bromide on the surface of the solid, which dissolves and re-oxidizes to Cr(III).

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References

Brauer, Georg (1965) [1962]. Handbuch Der Präparativen Anorganischen Chemie [Handbook of Preparative Inorganic Chemistry] (in German). 2. Stuttgart; New York, New York: Ferdinand Enke Verlag; Academic Press, Inc. p. 1340. ISBN 978-0-32316129-9. Retrieved 2014-01-10.
Perry, Dale L. (2011). Handbook of Inorganic Compounds, Second Edition. Boca Raton, Florida: CRC Press. p. 122. ISBN 978-1-43981462-8. Retrieved 2014-01-10.
NIOSH Pocket Guide to Chemical Hazards. "#0141". National Institute for Occupational Safety and Health (NIOSH).

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[German-1] Brauer, Georg (1965) [1962]. Handbuch Der Präparativen Anorganischen Chemie [Handbook of Preparative Inorganic Chemistry] (in German). 2. Stuttgart; New York, New York: Ferdinand Enke Verlag; Academic Press, Inc. p. 1340. ISBN 978-0-32316129-9. Retrieved 2014-01-10.

[Handbook-2] Perry, Dale L. (2011). Handbook of Inorganic Compounds, Second Edition. Boca Raton, Florida: CRC Press. p. 122. ISBN 978-1-43981462-8. Retrieved 2014-01-10.

[PGCH-3] NIOSH Pocket Guide to Chemical Hazards. "#0141". National Institute for Occupational Safety and Health (NIOSH).