trans-Bis(N′-isopropylidenebenzohydrazidato-κ2 N′,O)bis(pyridine-κN)nickel(II)

The complex molecule of the title compound, [Ni(C10H11N2O)2(C5H5N)2], has a crystallographically imposed centre of symmetry. The NiII atom is coordinated in a distorted octahedral geometry by the O and N atoms of two trans arranged anionic bidentate hydrazone ligands forming the equatorial plane and by the N atoms of two pyridine molecules at the axial positions. In the crystal, intermolecular C—H⋯N hydrogen bonds link the molecules into columns parallel to the b axis.

The complex molecule of the title compound, [Ni(C 10 H 11 -N 2 O) 2 (C 5 H 5 N) 2 ], has a crystallographically imposed centre of symmetry. The Ni II atom is coordinated in a distorted octahedral geometry by the O and N atoms of two trans arranged anionic bidentate hydrazone ligands forming the equatorial plane and by the N atoms of two pyridine molecules at the axial positions. In the crystal, intermolecular C-HÁ Á ÁN hydrogen bonds link the molecules into columns parallel to the b axis.

Comment
Hydrazones are an important class of Schiff bases compounds which has attracted much attention because of their biological activities (Carcelli et al., 1995), chemical and industrial versatility, and strong tendency to chelate to transition metals (Zhang et al., 2011;Ali et al., 2004;Cheng et al., 1996). As an extension of our work on the structural characterization of aroylhydrazone derivatives, the title compound was synthesized and its crystal structure is reported here.
In the title compound, the complex molecule has crystallographically imposed centre of symmetry (Fig. 1). The coordination polyhedron about the nickel metal is distorted octahedral, with the N, O atoms of two trans-arranged anionic bidentate hydrazone ligands at the equatorial plane and by the N atoms of two pyridine molecules occupying the axial positions. In the crystal structure, complex molecules are linked by intermolecular C-H···N hydrogen bonds (Table 1)

Experimental
Ethyl benzoate (6.00 g, 0.04 mol) was dissolved in ethnol (30 ml) at room temperature and heated at 363 K, followed by the addition of hydrazine hydrate (2.40 g, 0.048 mol). Subsequently, the mixture was refluxed for 9 h, and then cooled to room temperature. The crystals precipitated were collected by filtration. The product was recrystallized from ethanol and dried under reduced pressure to give benzoylhydrazine. Benzoylhydrazine (3.40 g, 0.025 mol) was dissolved in ethanol (20 ml) at room temperature and heated at 363 K, followed by the addition of dimethyl ketone (1.45 g, 0.025 mol). Subsequently, the mixture was refluxed for 10 h, and then cooled to room temperature. The solid phase precipitated was collected by filtration. The product was recrystallized from ethanol and dried under reduced pressure to give N'-[(E)-dimethylketone]benzohydrazide. A mixture of N'-[(E)-dimethylketone]-benzohydrazide (0.018 g, 0.10 mmol), NiC l2 .6H 2 O (0.024 g, 0.10 mmol), pyridine (0.0079 g, 0.10 mmol), H 2 O (5.00 ml) and several drop of methanol was placed in a Parr Teflon-lined stainless steel vessel (25 ml), and then the vessel was sealed and heated at 393 K for 3 d. After the mixture was slowly cooled to room temperature, red crystals suitable for X-ray analysis were obtained (yield 37%).

Refinement
All H atoms were positioned geometrically and treated as riding on their parent atoms,with C-H = 0.93-0.96 Å, and with U iso (H) = 1.2U eq (C) or 1.5U eq (C) for methyl H atoms.
supplementary materials sup-2 Figures Fig. 1. The molecular structure of the title compound, showing displacement ellipsoids drawn at the 30% probability level. H atoms are presented as small spheres of arbitrary radius. Symmetry code: (A) -x, 1-y, -z.