Dichlorido(3,5,5′-trimethyl-1,3′-bi-1H-pyrazole-κ2 N 2,N 2′)copper(II)

In the title complex, [CuCl2(C9H12N4)], the CuII atom exhibits a distorted square-planar coordination geometry involving two chloride ions and two N-atom donors from the bipyrazole ligand. The chelate ring including the CuII atom is essentially planar, with a maximum deviation of 0.0181 (17) Å for one of the coordinated N atoms. This plane forms a dihedral angle of 30.75 (6)° with the CuCl2 plane. In the crystal, each pair of adjacent molecules is linked into a centrosymmetric dimer by N—H⋯Cl hydrogen bonds. The crystal structure is stabilized by intermolecular C—H⋯N and C—H⋯Cl hydrogen bonds and weak slipped π–π stacking interactions between symmetry-related molecules, with an interplanar separation of 3.439 (19) Å and a centroid–centroid distance of 3.581 (19) Å.

In the title complex, [CuCl 2 (C 9 H 12 N 4 )], the Cu II atom exhibits a distorted square-planar coordination geometry involving two chloride ions and two N-atom donors from the bipyrazole ligand. The chelate ring including the Cu II atom is essentially planar, with a maximum deviation of 0.0181 (17) Å for one of the coordinated N atoms. This plane forms a dihedral angle of 30.75 (6) with the CuCl 2 plane. In the crystal, each pair of adjacent molecules is linked into a centrosymmetric dimer by N-HÁ Á ÁCl hydrogen bonds. The crystal structure is stabilized by intermolecular C-HÁ Á ÁN and C-HÁ Á ÁCl hydrogen bonds and weak slippedstacking interactions between symmetry-related molecules, with an interplanar separation of 3.439 (19) Å and a centroid-centroid distance of 3.581 (19) Å .
The ability of biheterocycles to form biochemically interesting complexes, with transition metals has prompted several researchers to test them in some areas: medicine (Bekhit & Abdel-Aziem, (2004); Sendai et al. 2000), agriculture (Das & Mittra, 1978) corrosion (Benabdallah et al. 2007) and as extractors of metals such as Cu 2+ , Cd 2+ and Pb 2+ (Attayibat et al. 2006). To better understand the interactions between the bipyrazoles and transition metals we have chosen to study some copper complex of bipyrazole possessing a Carbone-nitrogen bond between the two pyrazolics cycles.
The title molecule is built up from two interconnected five-membered rings as schown in Fig.1. Each of the two heterocyclic rings and the linked carbon are almost planar with a maximum deviations of -0.0101 (15) Å and -0.0107 (15) Å from N1 and N3 respectively. The dihedral angle between them is about 3.80 (9)°. The Cu II ion is surrounded by two nitrogen atoms belonging to the organic molecule and two chlorides which form a very distorted square planar.The values of adjacent angles around the Cu II ions are in the range 78.14 (5)-98.297 (16)° and 151.99 (4)-161.72 (4)° (Table 1), which confirms the distorted square-planar geometry. The chelate ring (N1-N2-C4-N3) and the copper atom are almost planar with a maximum deviations of 0.0181 (17) Å from C4 and build dihedral angle of 30.75 (6)° with the plane through the three ions: Cu II+ and two Cl -.
In the crystal, each pair of molecules linked by N4-H4···Cl1 hydrogen bonds form a dimer as schown in Fig.2 and table 2.

Experimental
The title compound was synthesized by mixing a solution of bipyrazole in methanol and an aqueous solution of cupric chloride with ligand/metal ratio of 2. Heating was maintaind for few minutes.Then a pinch of NaCl was added and heating was continued until the solution became clear. After a long time, green crystals were collected and dried over P2O5.   Fig. 1. The asymmetric unit of the title compound, with the atom-labeling scheme. Displacement ellipsoids are drawn at the 50% probability level. H atoms are represented as small spheres of arbitrary radii. 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 > 2σ(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.