Aluminium iodide is a chemical compound containing aluminium and iodine. Invariably, the name refers to a compound of the composition, formed by the reaction of aluminium and iodine[1] or the action of on 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, 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.[2]
Solid is dimeric, consisting of, similar to that of .[3] The structure of monomeric and dimeric forms have been characterized in the gas phase.[4] The monomer,, is trigonal planar with a bond length of 2.448(6) Å, and the bridged dimer,, at 430 K is a similar to and with 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 D2h.
See main article: Aluminium monoiodide. 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:[5]