Chromium(III) iodide

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 iodides.^[2]

Chromium(III) iodide

Names
IUPAC name Chromium(III) iodide
Other names Chromium triiodide, chromic iodide
Identifiers
CAS Number	13569-75-0
3D model (JSmol)	Interactive image
ChemSpider	75416
ECHA InfoCard	100.033.614
EC Number	236-991-3
PubChem CID	83586
CompTox Dashboard (EPA)	DTXSID50929111
InChI InChI=1S/Cr.3HI/h;3*1H/q+3;;;/p-3 Key: PPUZYFWVBLIDMP-UHFFFAOYSA-K InChI=1/Cr.3HI/h;3*1H/q+3;;;/p-3/rCrI3/c2-1(3)4 Key: PPUZYFWVBLIDMP-GXOYXQMQAU
SMILES [Cr](I)(I)I
Properties
Chemical formula	CrI3
Molar mass	432.7095 g·mol−1
Appearance	black solid
Density	5.32 g/cm3[1]
Melting point	> 600 °C (1,112 °F; 873 K)
Solubility in water	Soluble
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

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

Preparation and properties

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]

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.^[2]

Chromium triiodide can also be prepared as nanoplatelets^{[clarification needed]} from the alkoxide Cr(OC(CH₃)(C(CH₃)₃)₂)₃.^[4][how?]

Chromium triiodide was one of the first materials which was discovered to be a magnetic two-dimensional material that has great potentials for spintronics devices.^[5]