Stabilization of discrete [Cu(C2O4)2(H2O)2]2- dianions in the solid state by an extensive hydrogen bonded network

The dominant species in aqueous copper(II) solutions containing a high concentration of oxalate (ox) is trans[Cu(ox)(2)(H2O)(2) ](2-), yet the ability of the oxalate anion to bridge metal ions means that very few examples of this isolated anion are seen in solid state structures. The structure of [pipH(2)](2+)[Cu(ox)(2)(H2O)(2)](2-). 2H(2)O (pip = piperazine) (1) comprises discrete ions held in a complex 3-dimensional hydrogen bonded network.