Chromium(III) bromide

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Chromium(III) bromide
Kristallstruktur Bismut(III)-iodid.png
Names
IUPAC name
Chromium(III) bromide
Other names
Chromium tribromide, Chromium bromide, Chromic bromide
Identifiers
10031-25-1
13478-06-3 (hexahydrate)
ChemSpider 74280
EC number 233-088-6
Jmol-3D images Image
PubChem 82309
Properties
Br3Cr
Molar mass 291.71 g·mol−1
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)
insoluble in cold water, soluble with addition of Chromium(II) ion salts,[1] soluble in hot water[2]
Structure
Crystal structure trigonal
Except where noted otherwise, data is 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[edit]

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-doxidizes to Cr(III).

References[edit]

  1. ^ a b c d 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. 
  2. ^ a b c 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.