Aluminium iodide

Aluminium iodide

Ball and stick model of aluminium iodide dimer
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Names
Preferred IUPAC name Aluminium iodide
Other names Aluminium(III) iodide Aluminum iodide Aluminium triiodide Aluminum triiodide
Identifiers
CAS Number	7784-23-8 (anhydrate) Y 10090-53-6 (hexahydrate) Y
ChemSpider	74202 (anhydrate) Y
EC Number	232-054-8
Jmol 3D model	Interactive image
PubChem	82222 (anhydrate)
UN number	UN 3260
InChI InChI=1S/Al.3HI/h;3*1H/q+3;;;/p-3 Y Key: CECABOMBVQNBEC-UHFFFAOYSA-K Y InChI=1/Al.3HI/h;3*1H/q+3;;;/p-3 Key: CECABOMBVQNBEC-DFZHHIFOAE
SMILES I[Al](I)I
Properties
Chemical formula	AlI3
Molar mass	407.69495 g/mol (anhydrous) 515.786 g/mol (hexahydrate)
Appearance	colorless powder but impure samples are often brown
Density	3.98 g/cm3 (anhydrous) 2.63 g/cm3 (hexahydrate)
Melting point	189.4 °C (372.9 °F; 462.5 K) (anhydrous) 185 °C, decomposes (hexahydrate)
Boiling point	360 °C (680 °F; 633 K) , sublimes
Solubility in water	reacts violently (anhydrous) soluble (hexahydrate)
Solubility in alcohol, ether	soluble (hexahydrate)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Aluminium iodide is any chemical compound containing only aluminium and iodine. Invariably, the name refers to a compound of the composition AlI₃, formed by the reaction of aluminium and iodine or the action of HI on Al metal. The hexahydrate is obtained from a reaction between metallic aluminum or aluminum hydroxide with hydrogen iodide or hydroiodic acid. Like the related chloride and bromide, AlI₃ is a strong Lewis acid and will absorb water from the atmosphere. It is employed as a reagent for the scission of certain kinds of C-O and N-O bonds. It cleaves aryl ethers and deoxygenates epoxides.

Structure

Solid AlI₃ is dimeric, consisting of Al₂I₆, similar to that of AlBr₃. The structure of monomeric and dimeric forms have been characterized in the gas phase. The monomer, AlI₃ is trigonal planar with a bond length of 2.448(6) Å, and the bridged dimer, Al₂I₆ at 430 K is a similar to Al₂Cl₆ and Al₂Br₆ with Al-I bond lengths of 2.456(6) Å (terminal) and 2.670(8) Å (bridging). The dimer is described as floppy with an equilibrium geometry of D_2h.

Aluminium(I) iodide

The name "aluminium iodide" is widely assumed to describe the triiodide or its dimer. In fact, a monoiodide also enjoys a role in the Al-I system, although the compound AlI is unstable at room temperature relative to the triiodide

3 AlI → AlI₃ + 2 Al

An illustrative derivative of aluminium monoiodide is the cyclic adduct formed with triethylamine, AI₄I₄(NEt₃)₄.