cyclo-Tetrakis(μ-3-acetyl-4-methyl-1H-pyrazole-5-carboxylato-κ4 N 2,O 3:N 1,O 5)tetrakis[aquacopper(II)] tetradecahydrate

The title compound, [Cu4(C7H6N2O3)4(H2O)4]·14H2O, a tetranuclear [2 × 2] grid-type complex with S4 symmetry, contains four CuII atoms which are bridged by four pyrazolecarboxylate ligand anions and are additionally bonded to a water molecule. Each CuII atom is coordinated by two O atoms of the carboxylate and acetyl groups, two pyrazole N atoms of doubly deprotonated 3-acetyl-4-methyl-1H-pyrazole-5-carboxylic acid and one O atom of a water molecule. The geometry at each CuII atom is distorted square-pyramidal, with the two N and two O atoms in the equatorial plane and O atoms in the axial positions. O—H⋯O hydrogen-bonding interactions additionally stabilize the structure. One of the uncoordinated water molecules shows half-occupancy.

The title compound, [Cu 4 (C 7 H 6 N 2 O 3 ) 4 (H 2 O) 4 ]Á14H 2 O, a tetranuclear [2 Â 2] grid-type complex with S4 symmetry, contains four Cu II atoms which are bridged by four pyrazolecarboxylate ligand anions and are additionally bonded to a water molecule. Each Cu II atom is coordinated by two O atoms of the carboxylate and acetyl groups, two pyrazole N atoms of doubly deprotonated 3-acetyl-4-methyl-1H-pyrazole-5-carboxylic acid and one O atom of a water molecule. The geometry at each Cu II atom is distorted square-pyramidal, with the two N and two O atoms in the equatorial plane and O atoms in the axial positions. O-HÁ Á ÁO hydrogen-bonding interactions additionally stabilize the structure. One of the uncoordinated water molecules shows half-occupancy.
In the title compound, (I), the tetranuclear [2 × 2] grid-type complex with S4 symmetry are composed of four Cu II ions, four ligands and four metal-bound water molecules ( Fig. 1).
Each copper ion is nested in a square-pyramidal environment that is composed of the pyrazolate-N2, deprotonated carboxyl-O2 from a compartment of one ligand molecule and acetyl-O1 atoms, the pyrazolate-N1 from another ligand and one water-O4.
A part of the crystal packing of (I) is presented in Fig.2. In the crystal packing the complex molecules are associated via intermolecular hydrogen bonds that involve the O-H interactions between the coordinated and the solvate water molecules and the non-coordinating carboxylate-O atoms. Thus, the tetranuclear molecules are stacked along the crystallographic x and y axises, forming the columns. The columns bisect one another at right angles to give a layer-like structure.

Refinement
The O-H and N-H hydrogen atoms were located from the difference Fourier map, and refined with U iso = 1.5 U eq (parent atom). The remaining H atoms were positioned geometrically and were constrained to ride on their parent atoms with C-H = 0.96-0.97 Å, and with U iso = 1.2-1.5 U eq (parent atom).

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2sigma(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.