Chromium(III) iodide

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Chromium(III) iodide
Identifiers
CAS number 13569-75-0
Properties
Molecular formula CrI3
Molar mass 432.710 g/mol
Appearance black solid
Density 5.32 g/cm3[1]
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

Chromium(III) iodide, also known as chromium triiodide, is an inorganic compound with the formula CrI3. It is a black solid that is used to prepare other chromium compounds.[2]

Being isomorphous with chromium(III) chloride (CrCl3), it exhibits a cubic-closest packing arrangement in a double-layer crystal lattice. In this structure, chromium exhibits octahedral coordination geometry.[3]

Preparation and properties[edit]

Chromium triiodide is prepared by the direct reaction of chromium metal with an excess of iodine. The reaction is conducted at 500 °C:

2 Cr + 3 I2 → 2 CrI3

To obtain high purity samples, the product is thermally decomposed at 700 °C to sublime out chromium(II) iodide. The diiodide is then reiodinated.[2]

At room temperature, chromium triiodide is stable in contact with oxygen and moisture, but at temperatures approaching 200 °C it reacts with oxygen and releases iodine. Like CrCl3, the triiodide exhibits slow solubility in water owing to the kinetic inertness of Cr(III). Addition of small amounts of chromous iodide accelerates the dissolving process.

References[edit]

  1. ^ Perry, Dale L. (2011). Handbook of Inorganic Compounds, Second Edition. Boca Raton, Florida: CRC Press. p. 123. ISBN 978-1-43981462-8. Retrieved 2014-01-10. 
  2. ^ a b Gregory, N. W., Handy, L. L. "Chromium(III) iodide" Inorg. Synth. 1957, vol. 5, 128-130. doi:10.1002/9780470132364.ch34
  3. ^ Gregory, N. W., Handy, L. L. Structural Properties of Chromium(III) Iodide and Some Chromium(III) Mixed Halides" J. Am. Chem. Soc. 1952, vol. 74, pp. 891-893. doi:10.1021/ja01124a009