Aluminium iodide

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Aluminium iodide
Ball and stick model of aluminium iodide dimer
Jodid hlinitý.PNG
Preferred IUPAC name
Aluminium iodide
Other names
Aluminium(III) iodide

Aluminum iodide
Aluminium triiodide

Aluminum triiodide
3D model (JSmol)
ECHA InfoCard 100.029.140
EC Number 232-054-8
UN number UN 3260
Molar mass 407.69495 g/mol (anhydrous)
515.786 g/mol (hexahydrate)
Appearance white 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
very soluble,partial hydrolysis
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 AlI
, formed by the reaction of aluminium and iodine[1] 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
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 AlI
is dimeric, consisting of Al
, similar to that of AlBr3.[3] The structure of monomeric and dimeric forms have been characterized in the gas phase.[4] The monomer, AlI
is trigonal planar with a bond length of 2.448(6) Å, and the bridged dimer, Al
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 D2h.

Aluminium(I) iodide[edit]

Experiment showing a direct synthesis of aluminum iodide. Few drops of water are added to a homogenised mixture of aluminum powder and powdered iodine. After short time (an induction period) a vigorous reaction occurs followed by emission of intense colored vapors. The purple vapours are due to evaporation of iodine as a consequence of increased temperature of the system, and the brown ones are probably due to smoke of an adduct of the reaction product with excess of iodine. The exoenergetic reaction 2Al(s) + 3I2(s) → 2AlI3(s) is at the origin of the phenomenon observed.
Planned and performed by Marina Stojanovska, Miha Bukleski and Vladimir Petruševski, Department of Chemistry, FNSM, Ss. Cyril and Methodius University, Skopje, Macedonia.

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]

3 AlIAlI
+ 2 Al

An illustrative derivative of aluminium monoiodide is the cyclic adduct formed with triethylamine, Al


  1. ^ G. W. Watt; J. L. Hall (1953). Inorganic Syntheses. IV. pp. 117–119. 
  2. ^ M. Gugelchuk (2004). Aluminum Iodide, in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette). New York: J. Wiley & Sons. doi:10.1002/047084289X.ra083. 
  3. ^ Troyanov, Sergey I.; Krahl, Thoralf; Kemnitz, Erhard (2004). "Crystal structures of GaX3(X= Cl, Br, I) and AlI3". Zeitschrift für Kristallographie. 219 (2-2004): 88–92. ISSN 0044-2968. doi:10.1524/zkri. 
  4. ^ Hargittai, Magdolna; Réffy, Balázs; Kolonits, Mária (2006). "An Intricate Molecule: Aluminum Triiodide. Molecular Structure of AlI3and Al2I6 from Electron Diffraction and Computation". The Journal of Physical Chemistry A. 110 (10): 3770–3777. ISSN 1089-5639. doi:10.1021/jp056498e. 
  5. ^ Dohmeier, C.; Loos, D.; Schnöckel, H. (1996). "Aluminum(I) and Gallium(I) Compounds: Syntheses, Structures, and Reactions". Angewandte Chemie International Edition. 35: 129–149. doi:10.1002/anie.199601291.