Iron oxychloride explained

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 over the course of several days:

Fe₂O₃ + FeCl₃ → 3 FeOCl

Alternatively, FeOCl may be prepared by the thermal decomposition of FeCl₃⋅6H₂O at over the course of one hour:^[3]

FeCl₃ ⋅ 6H₂O → FeOCl + 5 H₂O + 2 HCl

Notes and References

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