Chromium(II) oxalate

Chromium(II) oxalate
Names
	IUPAC name Chromium(2+) oxalate
Identifiers
CAS Number	814-90-4 ;
3D model (JSmol)	Interactive image;
ChemSpider	12595;
ECHA InfoCard	100.011.282
PubChem CID	13147;
UNII	RV83VA978Q ;
CompTox Dashboard (EPA)	DTXSID90231083 ;
	InChI InChI=1S/C2H2O4.Cr/c3-1(4)2(5)6;/h(H,3,4)(H,5,6);/q;+2/p-2 Key: XVHFYNOGAFYRJV-UHFFFAOYSA-L; InChI=1/C2H2O4.Cr/c3-1(4)2(5)6;/h(H,3,4)(H,5,6);/q;+2/p-2 Key: XVHFYNOGAFYRJV-NUQVWONBAE;
	SMILES C(=O)(C(=O)[O-])[O-].[Cr+2];
Properties
Chemical formula	Cr(C2O4)
Molar mass	140.02 g/mol
Appearance	light green crystals
Density	2.461 g/cm3
Solubility in water	126 g/100 mL (0 °C)
Solubility	negligible in alcohol
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
	Infobox references

Chromium(II) oxalate is an inorganic compound with the chemical formula CrC₂O₄.

According to Nikumbh et al. CrC₂O₄.2H₂O can be prepared from chromium (II) sulfate pentahydrate by reaction with a mixture of sodium oxalate and oxalic acid in degassed aqueous solution. Their light green crystalline product was characterized by combustion elemental analysis, infrared spectroscopy, thermogravimetric analysis and powder X-ray diffraction. The measured magnetic moment of 4.65 B.M. suggests that the chromium ion does not form a Cr-Cr bond and has a high-spin octahedral coordination geometry. This would be consistent with the structure of other linear polymeric metal 2+ oxalates of general formula MC₂O₄.2H₂O, where M = Mg²⁺, Fe²⁺, etc. The chromium (II) dihydrate forms the anhydrous CrC₂O₄ when heated above 140 °C in an inert atmosphere. Heating above 320 °C produces a mixture of chromium oxides.

Milburn and Taube have presented data indicating that chromium (II) will reduce oxalate to glycolate within a few minutes in acidic aqueous solutions, casting some doubt on the formulation of chromium (II) oxalate as a stable Cr²⁺ species if prepared from acidic aqueous solutions.

References

A. K. Nikumbh, M.M. Rahman and A.D. Aware, Thermochimica Acta, 159 (1990) 109–123.

R. M. Milburn, and H. Taube, J. Phys. Chem., 1960, 64 (11), pp 1776–1776.

Xue-An Chen, Fang-Ping Song, Xin-An Chang, He-Gui Zanga and Wei-Qiang Xiao Acta Cryst. E64, 2008, m863.

Iron(II) oxalate

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