Crystal structure of bis{N′-[(E)-4-hydroxybenzylidene]pyridine-4-carbohydrazide-κN 1}diiodidocadmium methanol disolvate

In the title structure, the CdII atom is located on a twofold rotation axis and is coordinated by two I atoms and two N atoms of two carboxylate groups of two planar N′-[(E)-4-hydroxybenzylidene]pyridine-4-carbohydrazide ligands. N—H⋯O, O—H⋯O, C—H⋯O and C—H⋯I hydrogen bonding assembles the molecules into a three-dimensional network.

In the title compound, [CdI 2 (C 13 H 11 N 3 O 2 ) 2 ]Á2CH 3 OH, which crystallizes with Z = 4 in the space group Pbcn, the Cd II atom is located on a twofold rotation axis and coordinated by two I À anions and two N atoms from the pyridine rings of the two N 0 -[(E)-4-hydroxybenzylidene]pyridine-4-carbohydrazide ligands. The geometry around the Cd II atom is distorted tetrahedral, with bond angles in the range 94.92 (11)-124.29 (2) . The iodide anions undergo intermolecular hydrogen-bonding contacts with the C-H groups of the organic ligands of an adjacent complex molecule, generating a chain structure along the b axis. Furthermore, an extensive series of O-HÁ Á ÁO, N-HÁ Á ÁO and C-HÁ Á ÁO hydrogen-bonding interactions involving both the complex molecules and the ethanol solvate molecules generate a three-dimensional network.

Chemical context
Hydrazones are organic compounds that incorporate -NH-N=CH-units in their molecules. Hydrazone ligands based on pyridine are among the most important classes of flexible and versatile polydentate ligands and usually act as chelating ligands to metal cations , but in some cases they behave as monodentate ligands through the pyridine group alone. The hydrazone-based ligand in the title compound was prepared according to a method reported in the literature (Deng et al., 2005). The crystal structure of the ligand and three of its Zn II metal complexes have been reported previously . However, the title compound is the first reported crystal structure of a Cd II complex of the ligand.

Supramolecular features
In the crystal, the iodide anions form intermolecular C1-H1Á Á ÁI1 hydrogen-bonding contacts with the C-H groups of the pyridine rings of an adjacent complex molecule. This generates a a chain structure along the b axis. In addition, an extensive series of O-HÁ Á ÁO, N-HÁ Á ÁO and C-HÁ Á ÁO hydrogen-bonding interactions, Table 1, involving both the complex molecules and the methanol solvate molecules, generates a three-dimensional network (Figs. 2, 3 and 4).

Synthesis and crystallization
The title compound was synthesized by the reaction of a methanol solution of the ligand and Cd(NO 3 ) 2 Á4H 2 O in the presence of excess amount of NaI. The ligand (1 mmol, 0.240 g) and cadmium nitrate (1 mmol, 0.308 g) were placed in the main arm of a branched tube; sodium iodide (2 mmol, 0.300 g) was added to the mixture too. Methanol was carefully added to fill the arms. The tube was sealed and the ligandcontaining arm was immersed in an oil bath at 333 K while the branched arm was kept at ambient temperature. After 24 h, Figure 1 The molecular components of the title compound, showing the atomnumbering scheme. Displacement ellipsoids for non-H atoms are drawn at the 50% probability level [symmetry code: (a) Àx, y, Àz + 1 2 ]. Table 1 Hydrogen-bond geometry (Å , ). Symmetry codes: (ii) x þ 1 2 ; Ày þ 3 2 ; Àz; (iii) Àx þ 2; Ày þ 1; Àz; (iv) Àx À 1 2 ; y þ 1 2 ; z.

Figure 2
View of the hydrogen bonding and packing of the title compound along the a axis.

Figure 4
View of the hydrogen bonding and packing of the title compound along the c axis.

Figure 3
View of the hydrogen bonding and packing of the title compound along the b axis.
suitable single crystals had deposited in the cooler arm which were isolated and air dried.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. All C-bound H atoms were idealized (C-H = 0.98-0.99 Å ) and refined using the ridingmodel approximation with U iso (H) = 1.2 or 1.5 U eq (C). The N-H and O-H hydrogen atoms were located from difference maps and refined with the restraints N2-H2N = 0.77 (5)  Windows (Farrugia, 2012); software used to prepare material for publication: PLATON (Spek, 2009) and WinGX (Farrugia, 2012).  (2) 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 esds 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 > 2sigma(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.