Bis{2-amino-2-oxo-N-[(1E)-1-(pyridin-2-yl-κN)ethylidene]acetohydrazidato-κ2 N′,O 1}nickel(II)

In the title compound, [Ni(C9H9N4O2)2], the NiII ion is situated on a twofold rotation axis and is coordinated by two O and four N atoms from two tridentate {2-amino-2-oxo-N-[(1E)-1-(pyridin-2-yl-κN)ethylidene]acetohydrazidate ligands in a distorted octahedral geometry. In the crystal, N—H⋯O and N—H⋯N hydrogen bonds link the molecules into columns in [001]. The porous crystal packing is further stabilized via π–π interactions between the pyridine rings of neighbouring molecules [centroid–centroid distance = 3.746 (3) Å] with voids of 270 Å3.


Experimental
Crystal data [Ni(C 9 Table 1 Hydrogen-bond geometry (Å , ).  The bond C8-N3 which was simple in character becomes a double bond after deprotonation of the N-H function. The N imino -Ni-O1 and N pyridyl -Ni-N imino angles are 78.25 (13)° and 92.04 (13)° respectively. The deviation from 90° of the bond angles involving the chelation observed is presumably due to the formation of five-membered ring (Mikuriya et al., 1996).
In the crystal structure, the intermolecular hydrogen-bonding network involving the acetamide groups and also the N3 atom (Table 1), propagates parallel to the crystallographic c axis (Fig.2). This contributes to display a double inverted X molecular pattern in the ab plane stabilized by π -π stacking interactions between adjacent pyridine rings with the centroid-centroid distance of 3.746 (3) Å.
Experimental 2-Amino-2-oxo-N ′ -(1-(pyridin-2-yl)ethylidene)acetohydrazide (0.206 g, 1 mmol) was dissolved in 10 ml of ethanol and the LiOH (0.042 g, 2 mmol) was added with thorough shaking. To the resulting solution, Ni(CH 3 COO) 2 .4H 2 O (0.2489 g, 1 mmol) was added. Immediate change of the colour was observed. The mixture was stirred at room temperature during 2 h. The solution was filtered off and concentrated to tenth. Crystals that separated from the brown solution were filtered off and recrystallized in ethanol. On standing for three weeks, suitable X-rays crystals were obtained. Yield: 73.5%. Anal.

Refinement
All H atoms were located in difference maps. They were then treated as riding in geometrically idealized positions, with C-H = 0.93 (aryl), or 0.96 Å(CH 3 ) and N-H = 0.86 Å, and with U iso (H)=kU eq (C,N), where k = 1.5 for the methyl groups, and 1.2 for all other H atoms. Four low-resolution reflections were omitted due to beamstop shading (OMIT instruction in SHELX97-L)). Infinite cylindrical channels of 8 Å diameters ran through the crystal packing along the crystallographic c axis at positions x=0, y=1/2, z and x=1/2, y=0, z accounting for voids of 270 Å 3 per unit cell but no supplementary materials sup-2 Acta Cryst. (2012). E68, m553 solvent contribution to the X-ray diffraction was found.

Crystal data
[Ni (C 9  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. Five lowresolution reflections were omitted due to beamstop shading (OMIT instruction in SHELX97-L).
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )