Aluminium iodide

Aluminium iodide

Names
Preferred IUPAC name Aluminium iodide
Other names Aluminium(III) iodide Aluminum iodide Aluminium triiodide Aluminum triiodide
Identifiers
CAS Number	7784-23-8 (anhydrate) Y 10090-53-6 (hexahydrate) Y
3D model (JSmol)	Interactive image dimer: Interactive image
ChemSpider	74202 (anhydrate) Y
ECHA InfoCard	100.029.140
EC Number	232-054-8
PubChem CID	82222 (anhydrate)
UNII	L903Z8J9VR (anhydrate) Y VWS43EUO9V (hexahydrate) Y
UN number	UN 3260
CompTox Dashboard (EPA)	DTXSID0064838
InChI Key: CECABOMBVQNBEC-UHFFFAOYSA-K Y Key: CECABOMBVQNBEC-DFZHHIFOAE
SMILES I[Al](I)I dimer: I[Al-]1(I)[I+][Al-]([I+]1)(I)I
Properties
Chemical formula	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]
Solubility in water	very soluble, partial hydrolysis
Solubility in alcohol, ether	soluble (hexahydrate)
Structure[3]
Crystal structure	Monoclinic, mP16
Space group	P21/c, No. 14
Lattice constant	a = 1.1958 nm, b = 0.6128 nm, c = 1.8307 nm α = 90°, β = 90°, γ = 90°
Formula units (Z)	8
Thermochemistry[1]
Heat capacity (C)	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). N verify (what is YN ?) Infobox references

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]

Structure

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 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:^[7]

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

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