Bis(ethylenediaminium) bis[oxalohydroxamato(3-)]nickelate(II) dihydrate.

The title compound, (C2H10N2)2[Ni(C2HN2O4)2].2H2O, has an ionic structure containing a centrosymmetric complex 4- anion, charge-balancing ethylenediaminium dications and solvent water molecules. The oxalohydroxamate unit is triply deprotonated and forms five-membered chelate rings with the central Ni ion; the Ni ion lies on an inversion centre. The two hydroxamate O atoms in the complex anion are linked by short intramolecular hydrogen bonds.