Ferrous citrate, also known as iron(II) citrate or iron(2+) citrate, describes coordination complexes containing citrate anions with Fe2+ formed in aqueous solution. Although a number of complexes are possible (or even likely), only one complex has been crystallized. That complex is the coordination polymer with the formula [Fe(H2O)6]2+{[Fe(C6H5O7)(H2O)]}2.2H2O, where C6H5O73- is HOC(CH2CO2)2(CO2, i.e., the triple conjugate base of citric acid wherein the three carboxylic acid groups are ionized.[3] Ferrous citrates are all paramagnetic, reflecting the weak crystal field of the carboxylate ligands.[4]

Iron(II) citrate

Skeletal formula of iron(II) citrate

Powdered Iron(II) citrate hydrate
Names
IUPAC name
Iron(II) hydrogen 2-hydroxy-1,2,3-tricarboxylpropane
Other names
Iron(II) citrate, Ferrous citrate, Iron citrate
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.041.463 Edit this at Wikidata
EC Number
  • hydrogen citrate: 245-625-1
UNII
  • InChI=1S/C6H8O7.Fe/c7-3(8)1-6(13,5(11)12)2-4(9)10;/h13H,1-2H2,(H,7,8)(H,9,10)(H,11,12);/q;+2/p-2
    Key: APVZWAOKZPNDNR-UHFFFAOYSA-L
  • hydrogen citrate: C(C(=O)O)C(CC(=O)[O-])(C(=O)[O-])O.[Fe+2]
Properties
FeC6H6O7
Molar mass 245.95644 g/mol
Appearance slightly gray-green powder or white crystals[1] unstable
Density 1.91 g/cm3
Melting point decomposes[2]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Structure of the anionic coordination polymer {[Fe(C6H5O7)(H2O)]}n.[3] (legend: red = O, gray = C, blue = Fe, white = H).

Ferrous citrates are produced by treating disodium citrate Na
2
C
6
H
6
O
7
with sources of iron(II) aquo complexes, such as iron(II) sulfate.[5][2] Ferrous citrates are all highly unstable in air, converting to ferric citrates.

It is a nutrient supplement approved by the FDA.[6][7]

See also

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References

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  1. ^ Food Chemicals Codex. United States Pharmacopeial Convention. 2010. p. 396. ISBN 978-1-889788-86-9.
  2. ^ a b Perry, Dale L.; Phillips, Sidney L., eds. (1995). Handbook of Inorganic Compounds. Boca Raton, Florida: CRC Press. p. 167. ISBN 0-8493-8671-3.
  3. ^ a b Strouse, Jane; Layten, Steven W.; Strouse, Charles E. (1977). "Structural Studies of transition metal complexes of triionized and tetraionized citrate. Models for the coordination of the citrate ion to transition metal ions in solution and at the active site of aconitase". Journal of the American Chemical Society. 99 (2): 562–572. doi:10.1021/ja00444a041. PMID 830693.
  4. ^ Pierre, J. L.; Gautier-Luneau, I. (2000). "Iron and Citric Acid: A Fuzzy Chemistry of Ubiquitous Biological Relevance". Biometals. 13 (1): 91–96. doi:10.1023/A:1009225701332. PMID 10831230. S2CID 2301450.
  5. ^ "CFR - Code of Federal Regulations Title 21". www.fda.gov. U.S. Food and Drug Administration. 2013-06-01. Retrieved 2014-08-02.
  6. ^ PubChem. "Iron(II) citrate". pubchem.ncbi.nlm.nih.gov. Retrieved 2022-08-22.
  7. ^ "Substances Added to Food (formerly EAFUS)". www.cfsanappsexternal.fda.gov. Retrieved 2022-08-22.