Potassium ferrooxalate

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Potassium ferrooxalate
Names
IUPAC name
Potassium iron(II) oxalate
Other names
potassium ferrooxalate
potassium bisoxalatoferrate(II)
Identifiers
3D model (JSmol)
  • InChI=1S/2C2H2O4.Fe.2K/c2*3-1(4)2(5)6;;;/h2*(H,3,4)(H,5,6);;;/q;;+2;2*+1/p-4
    Key: LDRXJDFKHOUYMS-UHFFFAOYSA-J
  • [K+].[K+].O=C(-C(=O)O1)O[Fe-2]12OC(-C(=O)O2)=O
Properties
K
2[Fe(C
2O
4)
2] (anhydrous)
K
2[Fe(C
2O
4)
2]·2H
2O (dihydrate)
Appearance orange-yellow solid (anhydrous), golden-yellow crystals (dihydrate) [1]
Melting point decomposes at 470 °C [1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Potassium ferrooxalate, also known as potassium bisoxalatoferrate(II), is a salt with the formula K
2[Fe(C
2O
4)
2], sometimes abbreviated K
2FeOx
2. The ferrooxalate anion (negative ion) [Fe(C
2O
4)
2]2−
 is a transition metal complex, consisting of an atom of iron in the +2 oxidation state bound to two bidentate oxalate ions C
2O2−
4. The anion charge is balanced by two cations (positive ions) of potassium K+
.[1]

The anhydrous salt is orange-yellow and dissolves in water to give a red solution. Crystals of the dihydrate K
2[Fe(C
2O
4)
2]·2H
2O are golden yellow in color.[1]

Potassium ferrooxalate is believed to be formed when the related compound potassium ferrioxalate K
3[Fe(C
2O
4)
3] is decomposed by light in solution (a common method of actinometry) or heated above 296 °C.[1]

Preparation[]

While the ferrooxalate anion had been previously identified in solution, the solid salt was described only in 1992, by . He obtained it by dissolving the appropriate amounts of potassium oxalate dihydrate K
2C
2O
4·2H
2O and iron(II) oxalate dihydrate FeC
2O
4·2H
2O in boiling water, partially evaporating the red solution, and cooling it to room temperature, when gold-yellow crystals of K2Fe(ox)2·2H
2O precipitated. (The whole procedure should be performed in an oxygen-free atmosphere to avoid oxidation of the Fe2+
 core to Fe3+
.)[1]

Properties[]

Thermal decomposition[]

The dihydrate loses two water molecules at 200 °C.[1]

The anhydrous salt is stable in the absence of oxygen up to about 470 °C, when it decomposes into potassium oxalate and ferrous oxide FeO (which disproportionates partly into magnetite Fe
3O
4, metallic iron, and cementite Fe
3C).[1]

See also[]

A number of other iron oxalates are known

References[]

  1. ^ a b c d e f g h J. Ladriere (1992): "Mössbauer study on the thermal decomposition of potassium tris (oxalato) ferrate(III) trihydrate and bis (oxalato) ferrate(II) dihydrate". Hyperfine Interactions, volume 70, issue 1, pages 1095–1098. doi:10.1007/BF02397520
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