|CAS number||(anhydrate) , (hexahydrate)|
|UN number||UN 3260|
|Jmol-3D images||Image 1|
|Molar mass||407.69495 g/mol (anhydrous)
515.786 g/mol (hexahydrate)
but impure samples
are often brown
|Density||3.98 g/cm3 (anhydrous)
2.63 g/cm3 (hexahydrate)
|Melting point||189.4 °C (anhydrous)
185 °C, decomp. (hexahydrate)
|Boiling point||360 °C, sublimes|
|Solubility in water||reacts violently (anhydrous)
|Solubility in alcohol, ether||soluble (hexahydrate)|
|Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)|
|(what is: / ?)|
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 should be protected from the atmosphere.
The structure of solid AlI3 had been reported as a chain structure but a recent study reports the structure as being dimeric, Al2I6, similar to solid AlBr3. Gas Phase electron diffraction was used to study the structure of monomeric and dimeric forms. The monomer, AlI3 at 700 K is trigonal planar with a bond length of 2.448(6) Å, and the bridged dimer, Al2I6 at 430 K has a similar shape to dimers 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.
Applications in organic synthesis
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
Hydrolysis of aluminium triiodide will release some HI, which is corrosive. Lewis acids are skin irritants.
- G. W. Watt, J. L. Hall (1953). Inorganic Syntheses IV. pp. 117–119.
- Anthony John Downs (1993). Chemistry of Aluminium, Gallium, Indium, and Thallium. Springer. ISBN 0-7514-0103-X.
- 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. doi:10.1524/zkri.18.104.22.168320. ISSN 0044-2968.
- Hargittai, Magdolna; Réffy, Balázs; Kolonits, Mária (2006). "An Intricate Molecule: Aluminum Triiodide. Molecular Structure of AlI3and Al2I6from Electron Diffraction and Computation". The Journal of Physical Chemistry A 110 (10): 3770–3777. doi:10.1021/jp056498e. ISSN 1089-5639.
- 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.
- 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.