Aluminium iodide

Aluminium iodide is a chemical compound containing aluminium and iodine. Invariably, the name refers to a compound of the composition AlI
₃, 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, AlI
₃ 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 AlI
₃ is dimeric, consisting of Al
₂I
₆, similar to that of AlBr
₃. The structure of monomeric and dimeric forms have been characterized in the gas phase. The monomer, AlI
₃, is trigonal planar with a bond length of 2.448(6) Å, and the bridged dimer, Al
₂I
₆, at 430 K is a similar to Al
₂Cl
₆ and Al
₂Br
₆ 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:

${\displaystyle {\ce {3AlI -> AlI3 + 2Al}}}$

An illustrative derivative of aluminium monoiodide is the cyclic adduct formed with triethylamine, Al
₄I
₄(NEt
₃)
₄.

References

External links

• Media related to Aluminium iodide at Wikimedia Commons