Ferric oxalate
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| Systematic IUPAC name
iron(3+) ethanedioate (2:3) | |
| Other names
Iron(III) oxalate
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3D model (JSmol)
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| ChemSpider | |
| ECHA InfoCard | 100.019.047 |
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PubChem CID
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| UNII | |
CompTox Dashboard (EPA)
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| Properties | |
| C6Fe2O12 | |
| Molar mass | 375.747 g/mol |
| Appearance | Pale yellow solid (anhydrous) Lime green solid (hexahydrate) |
| Odor | odorless |
| Melting point | 365.1 °C (689.2 °F) |
| slightly soluble | |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references
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Ferric oxalate, also known as iron(III) oxalate, refers to inorganic compounds with the formula Fe2(C2O4)3(H2O)x but could also refer to salts of [Fe(C2O4)3]3-. Fe2(C2O4)3(H2O)x are coordination polymers with varying degrees of hydration. The coordination complex with the formula [Fe(C2O4)3]3- forms a variety of salts, a well-known example being potassium ferrioxalate. This article emphasizes the coordination polymers.
Structure
Tetrahydrate
According to X-ray crystallography of the tetrahydrate Fe2(C2O4)3 · 4 H2O, iron is octahedrally coordinated. The oxalate ligands are bridging: some through all four oxygen atoms, some with two oxygen atoms. Half of the water is lattice water, being situated between chains of Fe oxalates.
The Mössbauer spectrum of Fe2(C2O4)3 · 4 H2O exhibits a doublet with an isomer shift of 0.38 mm/s, and a quadrupole splitting of 0.40 mm/s, suggesting a high spin Fe3+ in distorted octahedral coordination.[1][2]
Production
Ferric oxalate may be produced by reaction of iron(III) hydroxide and solution of oxalic acid:
- 2Fe(OH)3 + 3H2C2O4 → Fe2(C2O4)3 + 6H2O
Uses
Dentistry
Like many oxalates, ferric oxalate has been investigated as a short-term treatment for dentin hypersensitivity.[3] It is used in certain toothpaste formulations; however, its effectiveness has been questioned.[4]
Photography
Ferric oxalate is used as the light-sensitive element in the Kallitype photographic printing process; and the platinotype process Platinum/Palladium Printing.
Batteries
Ferric oxalate tetrahydrate has been investigated as a possible cheap material for the positive electrode (cathode) for lithium-ion batteries. It can intercalate lithium ions at an average potential of 3.35 V, and has shown a sustainable capacity of 98 mAh/g.[1] Additionally, ferric oxalate is one synthetic precursor to lithium iron phosphate, a popular Li-ion battery cathode.
Organic synthesis
Ferric oxalate hexahydrate is used with sodium borohydride for radical Markovnikov hydrofunctionalization reactions of alkenes.[5]
See also
A number of other iron oxalates are known:-
References
- ^ a b c Ahouari, Hania; Rousse, Gwenaëlle; Rodríguez-Carvajal, Juan; Sougrati, Moulay-Tahar; Saubanère, Matthieu; Courty, Matthieu; Recham, Nadir; Tarascon, Jean-Marie (2015). "Unraveling the Structure of Iron(III) Oxalate Tetrahydrate and Its Reversible Li Insertion Capability". Chemistry of Materials. 27 (5): 1631–1639. doi:10.1021/cm5043149.
- ^ Rousse, G.; Rodríguez-Carvajal, J. (2016). "Oxalate-mediated long-range antiferromagnetism order in Fe2(C2O4)3·4H2O". Dalton Transactions. 45 (36): 14311–14319. doi:10.1039/C6DT02740G. PMID 27539964.
- ^ Gillam, D. G.; Newman, H. N.; Davies, E. H.; Bulman, J. S.; Troullos, E. S.; Curro, F. A. (2004). "Clinical evaluation of ferric oxalate in relieving dentine hypersensitivity". Journal of Oral Rehabilitation. 31 (3): 245–250. doi:10.1046/j.0305-182X.2003.01230.x. PMID 15025657.
- ^ Cunha-Cruz, J.; Stout, J. R.; Heaton, L. J.; Wataha, J. C. (29 December 2010). "Dentin Hypersensitivity and Oxalates: a Systematic Review". Journal of Dental Research. 90 (3): 304–310. doi:10.1177/0022034510389179. PMC 3144108. PMID 21191127.
- ^ Barker, Timothy (2001-04-15). "Ferric Oxalate Hexahydrate". Encyclopedia of Reagents for Organic Synthesis (1 ed.). Wiley. pp. 1–4. doi:10.1002/047084289X.rn02346. ISBN 978-0-471-93623-7. S2CID 225482606.