Names | |
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Preferred IUPAC name
Aluminium iodide | |
Other names
Aluminium(III) iodide
Aluminum iodide | |
Identifiers | |
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3D model (
JSmol)
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ChemSpider |
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ECHA InfoCard | 100.029.140 |
EC Number |
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PubChem
CID
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UNII |
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UN number | UN 3260 |
CompTox Dashboard (
EPA)
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Properties | |
AlI3, AlI3·6H2O (hexahydrate) | |
Molar mass | 407.695 g/mol (anhydrous) 515.786 g/mol (hexahydrate) [1] |
Appearance | white (anhydrous) or yellow powder (hexahydrate) [1] |
Density | 3.98 g/cm3 (anhydrous) [1] 2.63 g/cm3 (hexahydrate) [2] |
Melting point | 188.28 °C (370.90 °F; 461.43 K) (anhydrous) 185 °C, decomposes (hexahydrate) [1] [2] |
Boiling point | 382 °C (720 °F; 655 K) anhydrous, sublimes [1] |
very soluble, partial hydrolysis | |
Solubility in alcohol, ether | soluble (hexahydrate) |
Structure [3] | |
Monoclinic, mP16 | |
P21/c, No. 14 | |
a = 1.1958 nm, b = 0.6128 nm, c = 1.8307 nm α = 90°, β = 90°, γ = 90°
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Formula units (Z)
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8 |
Thermochemistry [1] | |
Heat capacity (C)
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98.7 J/(mol·K) |
Std molar
entropy (S⦵298) |
195.9 J/(mol·K) |
Std enthalpy of
formation (ΔfH⦵298) |
-302.9 kJ/mol |
Except where otherwise noted, data are given for materials in their
standard state (at 25 °C [77 °F], 100 kPa).
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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
[4] 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.
[5]
Solid AlI
3 is dimeric, consisting of Al
2I
6, similar to that of
AlBr
3.
[3] The structure of monomeric and dimeric forms have been characterized in the gas phase.
[6] 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 D2h.
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: [7]
An illustrative derivative of aluminium monoiodide is the cyclic
adduct formed with
triethylamine, Al
4I
4(NEt
3)
4.