Christmas Fern – Polystichum acrostichoides

by | Dec 9, 2023 | Ferns, NE Native Ferns

How Can We Help?
You are here:
< Back

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.
Categories
Table of Contents