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
Related compounds
Other cations	Iron(II) oxalate
	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.

Preparation

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, forming a light green crystalline product, which has been characterized by combustion elemental analysis, infrared spectroscopy, thermogravimetric analysis and powder X-ray diffraction.[1] 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(II) oxalates of general formula MC₂O₄·2H₂O (M = Mg, Fe, etc.).[2] The dihydrate loses water to form anhydrous CrC₂O₄ when heated above 140 °C in an inert atmosphere. Heating above 320 °C produces a mixture of chromium oxides.[1]

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.[3]

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References

Nikumbh AK, Rahman MM, Aware AD (1990). "A study of the thermal decomposition of chromium(II) oxalate dihydrate using direct current electrical conductivity measurements". Thermochimica Acta. 159: 109–123. doi:10.1016/0040-6031(90)80099-K.
Chen XA, Song FP, Chang XA, Zang HG, Xiao WQ (June 2008). "A new polymorph of magnesium oxalate dihydrate". Acta Crystallographica. Section E, Structure Reports Online. 64 (Pt 7): m863. doi:10.1107/S1600536808015870. PMC 2961852. PMID 21202738.
Milburn RM, Taube H (1960). "The Reduction of Oxalate by Chromium(Ii)1,2". The Journal of Physical Chemistry. 64 (11): 1776. doi:10.1021/j100840a513. ISSN 0022-3654.

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[Nikumbh-1] Nikumbh AK, Rahman MM, Aware AD (1990). "A study of the thermal decomposition of chromium(II) oxalate dihydrate using direct current electrical conductivity measurements". Thermochimica Acta. 159: 109–123. doi:10.1016/0040-6031(90)80099-K.

[2] Chen XA, Song FP, Chang XA, Zang HG, Xiao WQ (June 2008). "A new polymorph of magnesium oxalate dihydrate". Acta Crystallographica. Section E, Structure Reports Online. 64 (Pt 7): m863. doi:10.1107/S1600536808015870. PMC 2961852. PMID 21202738.

[3] Milburn RM, Taube H (1960). "The Reduction of Oxalate by Chromium(Ii)1,2". The Journal of Physical Chemistry. 64 (11): 1776. doi:10.1021/j100840a513. ISSN 0022-3654.