Aqua[bis(2-ethyl-5-methyl-1H-imidazol-4-yl-κN 3)methane]oxalatocopper(II) dihydrate

In the title compound, [Cu(C2O4)(C13H20N4)(H2O)]·2H2O, the CuII atom exhibits a distorted square-pyramidal geometry with the two N atoms of the imidazole ligand and the two O atoms of the oxalate ligand forming the basal plane, while the O atom of the coordinated water molecule is in an apical position. The CuII atom is shifted 0.232 (2) Å out of the basal plane toward the water molecule. The asymmetric unit is completed by two solvent water molecules. These water molecules participate in the formation of an intricate three-dimensionnal network of hydrogen bonds involving the coordinated water molecule and the NH groups.

In the title compound, [Cu(C 2 O 4 )(C 13 H 20 N 4 )(H 2 O)]Á2H 2 O, the Cu II atom exhibits a distorted square-pyramidal geometry with the two N atoms of the imidazole ligand and the two O atoms of the oxalate ligand forming the basal plane, while the O atom of the coordinated water molecule is in an apical position. The Cu II atom is shifted 0.232 (2) Å out of the basal plane toward the water molecule. The asymmetric unit is completed by two solvent water molecules. These water molecules participate in the formation of an intricate threedimensionnal network of hydrogen bonds involving the coordinated water molecule and the NH groups.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: DN2649).
the water molecule. The asymmetric unit is completed by two solvate water molecules. The distances and angles within the square pyramid framework agree with related structures (Beznischenko et al., 2007);Pajunen, 1981).
These water molecules participate to the formation of an intricated hydrogen bonds resulting in three dimensionnal network involving the coordinated water molecule and the NH groups (Table 1, Fig. 2).

Experimental
Crystals of the title compound were synthesized by the reaction between copper(II) nitrate trihydrate, potassium oxalate and 4,4'-methanediylbis(2-ethyl-5-methyl-1H-imidazole) ligand. Copper salt and oxalate chemicals used (reagent grade) were commercially available, the 4,4'-methanediylbis(2-ethyl-5-methyl-1H-imidazole) ligand was synthesized as described below . 0.2 mmol(48.4 mg) solid copper(II) nitrate trihydrate was added to a 15 ml aqueous solution of 0.1 mmol(16.6 mg) potassium oxalate under continuous stirring. The suspension was heated at 40-50 °C during 1 h. Then this suspension was mixed with a 5 ml EtOH solution of 0.1 mmol(23.2mg)4,4'-methanediylbis(2-ethyl-5-methyl-1H-imidazole). Finally, the blue solution which results from the mixture was filtered off and allowed to evaporate at room temperature (Delgado, et al.,2008). Single crystals of the title compound as blue prisms were grown from the solution by slow evaporation at room temperature within a few days.
The ligand 4,4'-methanediylbis(2-ethyl-5-methyl-1H-imidazole) was synthesized as follows: 4.35 g (30 mmol) 2-ethyl-5-methylimidazole was added to a solution of 1.5 g (15 mmol)glycine (40% in H 2 O). This suspension was vigorously stirred, and 3.1 g (30 mmol) formaldehyde (37% in H 2 O) was added dropwise. The resulting turbid mixture was made alkaline with a concentrated sodium hydroxide solution until a pH of 12 was reached (Bouwman, et al.,2000). The reaction mixture was stirred for 8 days at room temperature in a closed vessel. During which time a white solid formed. The white solid was collected by filtration, washed with acetonitrile and diethyl ether, and air-dry at room temperature.

Refinement
All H atoms attached to C atoms and N atom were fixed geometrically and treated as riding with C-H = 0.96 Å (methyl) or 0.97 Å (methylene) and N-H = 0.86 Å with U iso (H) = 1.2U eq (C or N) or U iso (H) = 1.5U eq (methyl) . H atoms of supplementary materials sup-2 water molecules were located in difference Fourier maps and included in the subsequent refinement using restraints (O-H= 0.85 (1)Å and H···H= 1.40 (2)Å) with U iso (H) = 1.5U eq (O). In the last cycles of refinement, they were treated as riding on their parent O atoms. Fig. 1. The asymmetric unit of (I) with the atom-labelling scheme. Displacement ellipsoids are drawn at the 30% probability level. H atoms are represented as small spheres of arbitrary radii. Hydrogen bonds are shown as dashed lines.

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 > σ(F 2 ) is used only for calculating Rfactors(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.