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) ; 10090-53-6 (hexahydrate) ;
3D model (JSmol)	Interactive image; dimer: Interactive image;
ChemSpider	74202 (anhydrate) ;
ECHA InfoCard	100.029.140
EC Number	232-054-8;
PubChem CID	82222 (anhydrate);
UNII	L903Z8J9VR (anhydrate) ; VWS43EUO9V (hexahydrate) ;
UN number	UN 3260
CompTox Dashboard (EPA)	DTXSID0064838 ;
	InChI Key: CECABOMBVQNBEC-UHFFFAOYSA-K ; 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 (So298)	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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	Infobox references

Aluminium iodide is any chemical compound containing only 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 $Al 2 I 6$ , similar to that of AlBr₃.[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, $Al 2 I 6$ 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 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]

3 AlI \to AlI 3 + 2 Al

An illustrative derivative of aluminium monoiodide is the cyclic adduct formed with triethylamine, $Al 4 I 4 (NEt 3) 4$ .

References

Haynes, William M., ed. (2011). CRC Handbook of Chemistry and Physics (92nd ed.). Boca Raton, FL: CRC Press. p. 4.45. ISBN 1439855110.
Perry, Dale L. (19 April 2016). Handbook of Inorganic Compounds, Second Edition. CRC Press. p. 8. ISBN 978-1-4398-1462-8.
Troyanov, Sergey I.; Krahl, Thoralf; Kemnitz, Erhard (2004). "Crystal structures of $GaX 3 (X= Cl, Br, I)$ and $AlI 3$ ". Zeitschrift für Kristallographie. 219 (2–2004): 88–92. doi:10.1524/zkri.219.2.88.26320.
Watt, George W; Hall, James L; Taylor, William Lloyd; Kleinberg, Jacob (1953). "Aluminum Iodide". Inorganic Syntheses. Inorganic Syntheses. 4. pp. 117–119. doi:10.1002/9780470132357.ch39. ISBN 9780470132357.
Gugelchuk, M. (2004). "Aluminum Iodide". In L. Paquette (ed.). Encyclopedia of Reagents for Organic Synthesis. New York: J. Wiley & Sons. doi:10.1002/047084289X.ra083.
Hargittai, Magdolna; Réffy, Balázs; Kolonits, Mária (2006). "An Intricate Molecule: Aluminum Triiodide. Molecular Structure of $AlI 3$ and $Al 2 I 6$ from Electron Diffraction and Computation". The Journal of Physical Chemistry A. 110 (10): 3770–3777. doi:10.1021/jp056498e.
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.

External links

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[b92-1] Haynes, William M., ed. (2011). CRC Handbook of Chemistry and Physics (92nd ed.). Boca Raton, FL: CRC Press. p. 4.45. ISBN 1439855110.

[Perry2016-2] Perry, Dale L. (19 April 2016). Handbook of Inorganic Compounds, Second Edition. CRC Press. p. 8. ISBN 978-1-4398-1462-8.

[TroyanovKrahl2004-3] Troyanov, Sergey I.; Krahl, Thoralf; Kemnitz, Erhard (2004). "Crystal structures of $GaX 3 (X= Cl, Br, I)$ and $AlI 3$ ". Zeitschrift für Kristallographie. 219 (2–2004): 88–92. doi:10.1524/zkri.219.2.88.26320.

[4] Watt, George W; Hall, James L; Taylor, William Lloyd; Kleinberg, Jacob (1953). "Aluminum Iodide". Inorganic Syntheses. Inorganic Syntheses. 4. pp. 117–119. doi:10.1002/9780470132357.ch39. ISBN 9780470132357.

[5] Gugelchuk, M. (2004). "Aluminum Iodide". In L. Paquette (ed.). Encyclopedia of Reagents for Organic Synthesis. New York: J. Wiley & Sons. doi:10.1002/047084289X.ra083.

[HargittaiRéffy2006-6] Hargittai, Magdolna; Réffy, Balázs; Kolonits, Mária (2006). "An Intricate Molecule: Aluminum Triiodide. Molecular Structure of $AlI 3$ and $Al 2 I 6$ from Electron Diffraction and Computation". The Journal of Physical Chemistry A. 110 (10): 3770–3777. doi:10.1021/jp056498e.

[7] 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.