Copper(II) oxalate

Copper(II) oxalate is an inorganic compound with the chemical formula CuC₂O₄•(H₂O)_x. The value of x lies between 0 (anhydrous form) and 0.44. One of these species is found as the secondary mineral moolooite (0.44 hydrate).^[4] The anhydrous compound has been characterized by X-ray crystallography.^[5] Many transition metal oxalate complexes are known.

Copper(II) oxalate

Names
Other names Copper (II) oxalate, cupric oxalate, copper(2+) ethanedioate
Identifiers
CAS Number	814-91-5 Y hemihydrate: 55671-32-4
3D model (JSmol)	Interactive image
ChemSpider	12596
ECHA InfoCard	100.011.283
EC Number	212-411-4
PubChem CID	54602330
UNII	BN136S94FS N
UN number	3077
CompTox Dashboard (EPA)	DTXSID0041802
InChI Key: QYCVHILLJSYYBD-UHFFFAOYSA-N InChI=1S/C2H2O4.Cu/c3-1(4)2(5)6;/h(H,3,4)(H,5,6);/q;+2
SMILES O=C([O-])C([O-])=O.[Cu+2]
Properties
Chemical formula	CuC 2O 4
Molar mass	151.56
Appearance	blue solid
Density	6.57 g/cm3
Solubility in water	insoluble
Solubility product (Ksp)	4.43×10−10[1]
Hazards
GHS labelling:
Pictograms	[2]
Signal word	Warning
Hazard statements	H302, H302+H312, H312
Precautionary statements	P264, P270, P280, P301+P312, P302+P352, P312, P322, P330, P363, P501
Thermochemistry
Std enthalpy of formation (ΔfH⦵298)	−751.3 kJ/mol[3]
Related compounds
Related compounds	Calcium oxalate Sodium oxalate Magnesium oxalate Strontium oxalate Barium oxalate Iron(II) oxalate Iron(III) oxalate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Copper(II) oxalate, whether anhydrous or hydrated, is practically insoluble in all solvents, as it is a coordination polymer.^[6]

Synthesis

Copper(II) oxalate can be produced by precipitation from acidified aqueous copper(II) salts and oxalic acidor an alkali metal oxalate.^[7][8]

CuSO₄ + H₂C₂O₄ + H₂O → CuC₂O₄·H₂O + H₂SO₄

Reactions

Upon heating to 130 °C, the hydrated copper(II) oxalates convert to the anhydrous cupric oxalate. Further heating at higher temperatures under an atmosphere of hydrogen gives copper metal, suitable as a reagent.^[7]

The hydrates bind Lewis bases.

Hydrated copper(II) oxalate reacts with alkali metal oxalates and ammonium oxalate to give bis(oxalato)cuprate:^[9]

(CuC₂O₄)(H₂O)_x + C₂O2−4 → [Cu(C₂O₄)₂]²⁻ + x H₂O

Uses

Copper oxalate is used as a catalyst for organic reactions, as a stabilizer for acetylated polyformaldehyde.^[10][11]

Related compounds

• Cuprous oxalates.^[12]