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 ligands and water.

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.

Dihydrate
The material K2Fe(C2O4)2(H2O)2 has been claimed but not verified.Potassium ferrooxalate is believed to be formed when the related compound potassium ferrioxalate [] is decomposed by light in solution (a common method of actinometry) or heated above 296 °C. The anhydrous salt is orange-yellow and dissolves in water to give a red solution. Crystals of the dihydrate []·2 are golden yellow in color.