Chemistry:Chromium(II) oxalate

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Chromium(II) oxalate
Names
IUPAC name
Chromium(2+) oxalate
Identifiers
3D model (JSmol)
ChemSpider
UNII
Properties
Cr(C2O4)
Molar mass 140.02 g/mol
Appearance light green crystals
Density 2.461 g/cm3
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]

References

  1. 1.0 1.1 "A study of the thermal decomposition of chromium(II) oxalate dihydrate using direct current electrical conductivity measurements" (in en). Thermochimica Acta 159: 109–123. 1990. doi:10.1016/0040-6031(90)80099-K. 
  2. "A new polymorph of magnesium oxalate dihydrate". Acta Crystallographica Section E 64 (Pt 7): m863. June 2008. doi:10.1107/S1600536808015870. PMID 21202738. 
  3. Milburn, Ronald M.; Taube, Henry (1960). "The Reduction of Oxalate by Chromium(Ii)1,2" (in en). The Journal of Physical Chemistry 64 (11): 1776. doi:10.1021/j100840a513. ISSN 0022-3654.