Potassium ferrooxalate

Potassium ferrooxalate, also known as potassium bisoxalatoferrate(II), is a salt with the formula K₂Fe(C₂O₄)₂(H₂O)_x. The anion is a transition metal oxalate complex, consisting of an atom of iron in the +2 oxidation state bound to oxalate (C
₂O²⁻
₄) ligands and water.^[2]

Potassium ferrooxalate

Names
IUPAC name Potassium iron(II) oxalate
Other names potassium ferrooxalate potassium bisoxalatoferrate(II)
Identifiers
CAS Number	28288-62-2 Y
3D model (JSmol)	Interactive image
InChI 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
SMILES [K+].[K+].O=C(-C(=O)O1)O[Fe-2]12OC(-C(=O)O2)=O
Properties
Chemical formula	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

Anhydrous K₂Fe(C₂O₄)₂ has been prepared by hydrothermal methods from ferrous chloride. It is a coordination polymer with trigonal prismatic Fe(C₂O₄)₃ centers. Half of the oxalate ligands are bridging.^[3]

Dihydrate

The material K₂Fe(C₂O₄)₂(H₂O)₂ has been claimed^[1] but not verified. 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] 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]

See also

A number of other iron oxalates are known

• Iron(II) oxalate
• Iron(III) oxalate
• Sodium ferrioxalate