Article · Wikipedia archive · Last revised Jun 13, 2026

Iron oxychloride

Iron oxychloride is the inorganic compound with the formula FeOCl. This purple solid adopts a layered structure, akin to that of cadmium chloride. The material slowly hydrolyses in moist air. The solid intercalates electron donors such as tetrathiafulvalene and even pyridine to give mixed valence charge-transfer salts. Intercalation is accompanied by a marked increase in electrical conductivity and a color change to black.

Last revised
Jun 13, 2026
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Citations
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Source
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Iron oxychloride
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Names
IUPAC name
Iron oxychloride
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.054.740
EC Number
  • 260-233-0
  • InChI=1S/ClH.Fe.O/h1H;;/q;+1;/p-1 ☒N
    Key: YPLPZEKZDGQOOQ-UHFFFAOYSA-M ☒N
  • O=[Fe]Cl
Properties
ClFeO
Molar mass 107.29 g·mol−1
Appearance Vivid, dark violet, opaque crystals
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Iron oxychloride is the inorganic compound with the formula FeOCl. This purple solid adopts a layered structure, akin to that of cadmium chloride.1 The material slowly hydrolyses in moist air. The solid intercalates electron donors such as tetrathiafulvalene and even pyridine to give mixed valence charge-transfer salts. Intercalation is accompanied by a marked increase in electrical conductivity and a color change to black.2

Production

FeOCl is prepared by heating iron(III) oxide with ferric chloride at 370 °C (698 °F) over the course of several days:2

Fe2O3 + FeCl3 → 3 FeOCl

Alternatively, FeOCl may be prepared by the thermal decomposition of FeCl3⋅6H2O at 220 °C (428 °F) over the course of one hour:3

FeCl3 ⋅ 6H2O → FeOCl + 5 H2O + 2 HCl
References

References

  1. Lind, M. D. (1970-08-15). "Refinement of the crystal structure of iron oxychloride". Acta Crystallographica Section B. 26 (8): 1058–1062. doi:10.1107/s0567740870003618.
  2. Kikkawa, S.; Kanamaru, F.; Koizumi, M.; Rich, Suzanne M.; Jacobson, Allan (1984-01-01). Holt, Smith L. Jr. (ed.). Layered Intercalation Compounds. John Wiley & Sons. pp. 86–89. doi:10.1002/9780470132531.ch17. ISBN 978-0-470-13253-1.
  3. Chen, C.; Yu, T.; Yang, M.; Zhao, X.; Shen, X. (2019). "An All-Solid-State Rechargeable Chloride Ion Battery". Advanced Science. 6 1802130. doi:10.1002/advs.201802130. PMC 6425448.