Dibromido{N′-[1-(pyridin-2-yl)ethylidene]picolinohydrazide-κ2 N′,O}cadmium

The title compound, [CdBr2(C13H12N4O)], was obtained from the reaction of Cd(NO3)2·4H2O with methyl(pyridin-2-yl)methanone picolinoylhydrazone and sodium bromide. The Cd2+ cation is ligated by one O atom and two N atoms of the tridentate ligand and two bromide anions, forming a Br2CdN2O polyhedron with a distorted trigonal–bipyramidal coordination geometry. In the crystal, non-classical C—H⋯Br hydrogen bonds are observed. In addition, π–π stacking interactions [centroid–centroid distance = 3.7455 (19) Å] contribute to the stabilization of the crystal structure.


Experimental
Crystal data [CdBr 2 (C 13 Table 1 Hydrogen-bond geometry (Å , ). Recently, the relative unsymmetrical tridentate Schiff base ligands and their hydrogenated derivatives have been introduced into the coordination chemistry to assemble polymers with beautiful molecular structures. Some organic Ndonor ligands are often chosen to fabricate these various complexes. In this connection, some complexes with similar tridentate ligands have been studied (Kasuga et al., 2001;Chen et al., 2005;Datta et al., 2011). Herein, we report the structure of a new cadmium complex based on a pyridine based tridentate Schiff base ligand.
The molecular structure of title compound is shown in Fig. 1. The Cd ion is five coordinated forming a distorted trigonal-bipyramidal coordination sphere, in which three positions are occupied by two N atoms and one O atom from the tridentate Schiff base ligand, and two positions coming from two bromide ions. As can be seen in Fig. 1, all non-H atoms of the tridentate Schiff base ligand are nearly coplanar, with maximum deviations of -0.053 (4) Å for C7 and 0.049 (2) Å for N2.

Experimental
The potentially tridenatate ligand methyl-2-pyridyl ketone picolinoyl hydrazone was obtained by condensation of methyl-2-pyridyl ketone and picolinic acid hydrazide with the ratio 1:1 in methanol. The title compound C 13 H 12 Br 2 CdN 4 O has been synthesized by the reaction of methanolic solution of the ligand and Cd(NO 3 ) 2 .4H 2 O in the presence of excess amount of NaBr. The ligand (1 mmol, 0.240 g) and cadmium nitrate (1 mmol, 279 g) were placed in main arm of a branched tube; sodium bromide (2 mmol, 0.206 g) was added to the mixture too. Methanol was carefully added to fill the arms. The tube was sealed and the ligand-containing arm was immersed in an oil bath at 333 K while the branched arm was kept at ambient temperature. After five days, suitable single crystals, were deposited in the cooler arm which were isolated, filtered off, washed with acetone and ether and air dried.

Refinement
H atoms bonded to C atoms were positioned geometrically and treated as riding with C-H = 0.93 Å and U iso (H) = 1.2U eq (C) for aromatic H, and C-H = 0.96 Å and U iso (H) = 1.5U eq (C) for methyl H.

Figure 1
The molecular structure of the title compound with the atom numbering scheme. Displacement ellipsoids for non-H atoms are drawn at the 50% probability level.   Special details Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles Refinement. Refinement on F 2 for ALL reflections except those flagged by the user for potential systematic errors. Weighted R-factors wR and all goodnesses 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 observed criterion of F 2 > σ(F 2 ) is used only for calculating -R-factor-obs 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