Iron(III) iodide is an inorganic compound with the chemical formula FeI3. It is a thermodynamically unstable compound that is difficult to prepare. Nevertheless, iron(III) iodide has been synthesised in small quantities in the absence of air and water.[1]
| Names | |
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| IUPAC name
Iron(III) iodide
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| Other names
Ferric iodide
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| Identifiers | |
3D model (JSmol)
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| ChemSpider | |
PubChem CID
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CompTox Dashboard (EPA)
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| Properties | |
| FeI3 | |
| Molar mass | 436.56 g/mol |
| Appearance | Black solid |
| decomposes | |
| Solubility | sparingly soluble in dichloromethane |
| Related compounds | |
Other anions
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FeF3, FeCl3, FeBr3 |
Other cations
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ScI3, TiI3, VI3, MoI3, WI3, RhI3, BiI3 |
Related compounds
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FeI2 |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Preparation
editIron(III) and iodide tend to undergo a redox reaction[1] in which Fe3+ is reduced to Fe2+ and I− is oxidised to I2. This reaction can be avoided and iron(III) iodide can be synthesised by a photochemical reaction. Iron pentacarbonyl reacts with excess iodine in hexane under argon, releasing carbon monoxide and forming the complex diiodotetracarbonyliron(II), Fe(CO)4I2, as a light red solution.[1][2]
- Fe(CO)5 + I2 → Fe(CO)4I2 + CO
This complex then undergoes oxidative photodecarbonylation at −20 °C in the presence of further iodine and actinic light. A black film of FeI3 is deposited as further carbon monoxide is evolved.[1][2]
- Fe(CO)4I2 + ½I2 + hν → FeI3 + 4CO
Reactivity
editIron(III) iodide is prone to light-induced decomposition to iron(II) iodide and iodine.[2][3][4]
- FeI3 + hν → FeI2 + ½I2
Donor solvents such as tetrahydrofuran, acetonitrile, pyridine and water also promote this reaction: iron(III) iodide is extremely hygroscopic. It is sparingly soluble in dichloromethane. It reacts with iodide to form the tetraiodoferrate(III) ion.[2]
- FeI3 + I− → FeI4−
Iron(III) iodide undergoes ligand exchange or metathesis with certain alkyl chlorides to reversibly form iron(III) chloride and the corresponding alkyl iodides.[2]
- FeI3 + 3 RCl ⇌ FeCl3 + 3 RI
Adducts of FeI3 are well known. An orange complex can be prepared from FeI2 and I2 in the presence of thiourea.[5][6] Iron powder reacts with iodine-containing proligands to also give adducts of ferric iodide.[7]
See also
edit- Iron(II) iodide, FeI2
References
edit- ^ a b c d Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. pp. 1083–1084. ISBN 978-0-08-037941-8.
- ^ a b c d e Yoon, K. B.; Kochi, J. K. (1990). "Ferric iodide as a nonexistent compound". Inorg. Chem. 29 (4): 869–874. doi:10.1021/ic00329a058.
- ^ Šima, Jozef; Brezová, Vlasta (2002). "Photochemistry of iodo iron(III) complexes". Coord. Chem. Rev. 229 (1–2): 27–35. doi:10.1016/S0010-8545(02)00018-8.
- ^ Housecroft, C. E.; Sharpe, A. G. (2008). Inorganic Chemistry (3rd ed.). Prentice Hall. p. 716. ISBN 978-0-13-175553-6.
- ^ Pohl, Siegfried; Bierbach, Ulrich; Saak, Wolfgang (1989). "FeI3SC(NMe2)2, a Neutral Thiourea Complex of Iron(III) Iodide". Angew. Chem. Int. Ed. 28 (6): 776–777. doi:10.1002/anie.198907761.
- ^ Pohl, S.; Opitz, U.; Saak, W.; Haase, D. (1993). "Komplexe von FeI2 und FeI3 mit Tetramethylharnstoff". Z. Anorg. Allg. Chem. 619 (3): 608–612. doi:10.1002/zaac.19936190329.
- ^ Barnes, Nicholas A.; Godfrey, Stephen M.; Ho, Nicholas; McAuliffe, Charles A.; Pritchard, Robin G. (2013). "Facile synthesis of a rare example of an iron(III) iodide complex, [FeI3(AsMe3)2], from the reaction of Me3AsI2 with unactivated iron powder". Polyhedron. 55: 67–72. doi:10.1016/j.poly.2013.02.066.