Pentaaqua(chelidonato-O-4)copper(II) monohydrate

In crystals of pentaaqua(4-oxo-4H-pyran-2,6-dicarboxylato-O-4)copper(II) hy drate, [Cu(C7H2O6)(H2O)(5)]. H2O, the Cu-II cation is surrounded by an elon gated O-6 octahedron. The chelidonate anion (chel, [C5H2O2(COO)(2)](2-)) bi nds to the metal centre through the carbonyl rather than a carboxylate oxyg en, and forms a long axial bond Cu-O bond [2.6746 (16) Angstrom]. The axial Cu-O-aqua is also relatively long [2.3763(15)Angstrom]. The molecular asse mbly in the crystal is stabilized by a complex three-dimensional network of intermolecular O-H ... O bonds [O ... O 2.597 (2)-2.851 (2) Angstrom], the water molecules providing the donors, and the carboxylate and carbonyl gro ups of the chel Ligand most of the accepters, of the hydrogen bonding.