Iron(III) iodide

Iron(III) iodide
Names
IUPAC name
Iron(III) iodide
Other names
Ferric iodide
Identifiers
3D model (JSmol)
ChemSpider
  • InChI=1S/Fe.3HI/h;3*1H/q+3;;;/p-3
    Key: HEJPGFRXUXOTGM-UHFFFAOYSA-K
  • [Fe+3].[I-].[I-].[I-]
Properties
FeI3
Molar mass 436.56 g/mol
Appearance Black solid
decomposes
Solubility sparingly soluble in dichloromethane
Related compounds
Other anions
 FeF3, FeCl3, FeBr3
Other cations
 ScI3, TiI3, VI3, MoI3, WI3, RhI3, BiI3
Related compounds
 FeI2
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

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]

Preparation

Iron(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

Iron(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

References

  1. ^ 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.
  2. ^ 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.
  3. ^ 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.
  4. ^ Housecroft, C. E.; Sharpe, A. G. (2008). Inorganic Chemistry (3rd ed.). Prentice Hall. p. 716. ISBN 978-0-13-175553-6.
  5. ^ 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.
  6. ^ 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.
  7. ^ 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.