N,N′-Disalicyloylhydrazine

The approximately planar molecule of the title compound, C14H12N2O4, is centrosymmetric and has an E configuration with respect to the N—N bond. This compound adopts the ketoamine form with C=O and C—N distances of 1.233 (3) and 1.331 (4) Å, respectively. Adjacent molecules are assembled into a two-dimensional supramolecular structure parallel to the (101) plane via intermolecular O—H⋯O hydrogen bonds.

The approximately planar molecule of the title compound, C 14 H 12 N 2 O 4 , is centrosymmetric and has an E configuration with respect to the N-N bond. This compound adopts the ketoamine form with C O and C-N distances of 1.233 (3) and 1.331 (4) Å , respectively. Adjacent molecules are assembled into a two-dimensional supramolecular structure parallel to the (101) plane via intermolecular O-HÁ Á ÁO hydrogen bonds.

Comment
Aroylhydrazine ligands have recently gained the increasing concern due to their quite interesting chemical activities (John et al., 2006;Dou et al., 2006). However, most of the studies are focused on unsymmetrical aroylhydrazine, while symmetrical diaroylhydrazines receive much less attention (Bernhardt et al., 2005). In order to explore the impact of the structural character of symmetrical ligands on the properties of the complexes, the title compound, was synthesized by the self-combination of salicyloylhydrazine on the acidic environment.
The title molecule has crystallographic inversion symmetry ( Fig. 1) and goes near to co-planar with the mean deviation of 0.0584Å from the least-squares plane of all non-hydrogen atoms. An E configuration with respect to the N-N bond is observed. The distance of C1-O1 is 1.233 (3) Å, typical of a double bond, whereas the distances of C1-N1 and N1-N1 i at 1.331 (4)Å and 1.373 (4) Å, respectively are typical for a single bond (Table. 1), which is in agreement with that of the analogous compound , suggesting this diaroylhydrazine exists in the ketoamino form. All oxygen atoms in the title compound participate in intermolecular H-bond interactions with their neighbors, leading to one molecule bound with four molecules through O-H···O interactions. The dihedral angle of two adjacent molecules linked by O-H···O hydrogen bond is 65.7°. In such a recognition pattern, the two-dimensional network structure is assembled parallel to the (1 0 1) plane, as shown in Fig. 2.

Experimental
The salicyloylhydrazine(6.08 g, 40 mmol) was added to the solution of ice acetic acid(3 ml) in methanol(20 ml). After refluxed for three hours, the mixture was filtrated. Then colorless needle crystals suitable for X-ray diffraction were obtained by vaporizing the filtrate at room temperature. Yield

Refinement
The H atoms on the ligands were allowed to ride on their parent atoms with C(sp 2 hybrid)-H distances of 0.93 Å and U iso (H)=1.2U eq (C). Fig. 1. The molecular structure of the title compound. Displacement ellipsoids are drawn at the 30% probability level. Symmetry code (i): −x + 2,-y + 1,-z + 1