Dichlorido{2-[(E)-phenyl(pyridin-2-yl-κN)methylidene]-N-phenylhydrazinecarboxamide-κ2 N 2,O}copper(II)

The title compound, [CuCl2(C19H16N4O)], contains a CuII atom N,N′,O-chelated by a neutral N-phenylhydrazinecarboxamide ligand and additionally coordinated by two Cl atoms, resulting in a distorted square-pyramidal geometry. The ligating atoms in the basal square plane of the complex comprise the azomethine N, the pyridine N, the amide O and one of the Cl atoms, whereas the other Cl atom occupies an apical position. The apical Cl atoms in adjacent layers function as hydrogen-bond acceptors to both NH groups. Intermolecular C—H⋯Cl and C—H⋯O interactions are also observed.


Comment
Semicarbazones with versatile structural features are good ligands in both the neutral and anionic forms. Among the semicarbazones with diverse pharmacological activities (Beraldo & Gambino, 2004;Kasuga et al., 2006;Rivadeneira et al., 2009), the aryl semicarbazones were found to be devoid of sedative hypnotic activity and exhibited anticonvulsant activity with less neurotoxicity (Shalini et al., 2009). The biological activity can be attributed to their ability to form chelates with transition metal ions by bonding via ′O′ and azomethine ′N′ atoms. Also, the chlorido complex of imidazole-2-carbaldehyde semicarbazone has been found to exhibit antimicrobial activity (Rodriguez-Arguelles et al., 2010).
The title compound ( Fig. 1) crystallizes in the triclinic space group P1. The molecule adopts an E configuration with respect to C6═N2 bond and the tridentate ligand has its coordinating entities disposed in a cis fashion to each other.
The copper atom in the complex is N,N′,O chelated by the neutral semicarbazone (Kunnath et al., 2012). form. In addition to bond length and bond angle analysis, the trigonality index value confirms the coordination polyhedron to be a distorted square pyramidal (Addison et al., 1984), with the apical chlorine atom out of the square plane by a distance of 2.450 Å. The apical chlorine atoms of the adjacent complex units function as hydrogen bond acceptors, generating a centrosymmetric dimer through a cyclic R 2 1 (6) association (Etter et al., 1990). In addition to that a non-classical intermolecular C-H···Cl and an intramolecular C-H···O hydrogen bonds are also present in the molecular system ( Fig. 2, Table 1).
Since the Cg-Cg distances are greater than 4 Å, the short ring interactions are not significant. Fig. 4 shows the packing diagram of the title compound along c axis.

Experimental
The title compound was prepared by adapting a reported procedure (Kurup et al., 2011). To the semicarbazone ligand synthesized by refluxing a mixture of hot methanolic solutions (25 ml) of 4-phenylsemicarbazide (0.151 g, 1 mmol) and 2-benzoylpyridine (0.183 g, 1 mmol), hot filtered methanolic solution (25 ml) of CuCl 2 ·2H 2 O (0.170 g, 1 mmol) was added and refluxed for 2 h. The resulting green solution was cooled to room temperature. Green block shaped crystals were collected, washed with few drops of methanol and dried over P 4 O 10 in vacuo. Single crystals suitable for X-ray analysis were obtained after slow evaporation of solution in air for few days. The compound was obtained in 75% yield (0.3375 g).

Refinement
All H atoms on C were placed in calculated positions, guided by difference maps, with C-H bond distances of 0.93 Å. H atoms were assigned U iso (H) values of 1.2Ueq(carrier). Omitted owing to bad disagreement was reflection (0 0 1). H atoms of N3-H3′ and N4-H4′ bonds were located from difference maps and the bond distances are restrained to 0.88±0.02 Å.

Figure 1
ORTEP view of the title compound, drawn with 50% probability displacement ellipsoids for the non-H atoms.  Cu-Cl···π interaction found in the title compound.

Figure 4
A view of the unit cell along c axis.

Special details
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq