Potassium ferrioxalate

Potassium ferrioxalate is a chemical compound with the formula K3. It often occurs as the trihydrate K3 · 3H2O. Both are crystalline compounds, lime green in colour. , also known as potassium trisoxalatoferrate or potassium tris(oxalato)ferrate(III). Potassium ferrioxalate is a chemical compound with the formula K3. It often occurs as the trihydrate K3 · 3H2O. Both are crystalline compounds, lime green in colour. , also known as potassium trisoxalatoferrate or potassium tris(oxalato)ferrate(III). The compound is a salt consisting of ferrioxalate anions, 3−, and potassium cations K+. The anion is a transition metal complex consisting of an iron atom in the +3 oxidation state and three bidentate oxalate ions C2O2−4 anions acting as ligands. Potassium acts as a counterion, balancing the −3 charge of the complex. In solution, the salt dissociates to give the ferrioxalate anion, 3−, which appears fluorescent green in color. The ferrioxalate anion is quite stable in the dark, but is decomposed by light and higher-energy electromagnetic radiation. This feature is exploited for chemical actinometry, the measure of light flux, and for the preparation of blueprints. The complex can be synthesized by the reaction between iron(III) sulfate, barium oxalate and potassium oxalate: The reactants are combined in water, the solid precipitate of BaSO4 is removed, and the green trihydrate crystallizes from the cooled solution. Another common synthesis is reacting aqueous iron(III) chloride hexahydrate and potassium oxalate monohydrate. The structures of the trihydrate and of the anhydrous salt have been extensively studied. which indicates that the Fe(III) is high spin; as the low spin complex would display Jahn–Teller distortions. The ammonium and mixed sodium-potassium salts are isomorphous, as are related complexes with Al3+, Cr3+, and V3+. The ferrioxalate complex displays helical chirality as it can form two non-superimposable geometries. In accordance with the IUPAC convention, the isomer with the left-handed screw axis is assigned the Greek symbol Λ (lambda). Its mirror image with the right-handed screw axis is given the Greek symbol Δ (delta). The ferrioxalate anion is sensitive to light and to higher-energy electromagnetic radiation, including X-rays and gamma rays. Absorption of a photon causes the decomposition of one oxalate to carbon dioxide CO2 and reduction of the iron(III) atom to iron(II).