Crystal structure of trans-di-aqua-bis-(1H-pyrazole-3-carboxyl-ato-κ(2) N,O)copper(II) dihydrate.

In the title compound, [Cu(C4H3N2O2)2(H2O)2]·2H2O, the Cu(II) ion is located on an inversion centre and exhibits an axially elongated octa-hedral coordination geometry. The equatorial plane is formed by two N,O-bidentate 1H-pyrazole-3-carboxyl-ate ligands in a trans configuration. The axial positions are occupied by two water mol-ecules. The mononuclear complex mol-ecules are arranged in layers parallel to the ab plane. Each complex mol-ecule is linked to four adjacent species through inter-molecular O-H⋯O and N-H⋯O hydrogen bonds that are established between the coordinating water mol-ecules and carboxyl-ate O atoms or protonated N atoms of the organic ligands. These layers are further connected into a three-dimensional network by additional hydrogen bonds involving solvent water mol-ecules and non-coordinating carboxyl-ate O atoms.