Methyl 2-[(E)-(4-nitrophenyl)hydrazono]-3-oxobutyrate

The molecule of the title compound, C11H11N3O5, exists as the E isomer as it is stabilized by an intramolecular hydrogen bond. Except for the methyl H atoms, all atoms lie in special positions on a mirror plane and form a large conjugated system; the methyl H atoms are disordered about the mirror plane. In the crystalline state, bifurcated intra- and intermolecular N—H⋯O hydrogen bonds and four intermolecular C—H⋯O hydrogen bonds link the molecules into large perfectly planar sheets. Along the c axis, the N—N bond center approaches the phenyl-ring centroids of its neighbouring molecules above and below to give π–π overlap (at a distance of ca 3.57 Å), thus fusing the molecules into a three-dimensional framework.

The molecule of the title compound, C 11 H 11 N 3 O 5 , exists as the E isomer as it is stabilized by an intramolecular hydrogen bond. Except for the methyl H atoms, all atoms lie in special positions on a mirror plane and form a large conjugated system; the methyl H atoms are disordered about the mirror plane. In the crystalline state, bifurcated intra-and intermolecular N-HÁ Á ÁO hydrogen bonds and four intermolecular C-HÁ Á ÁO hydrogen bonds link the molecules into large perfectly planar sheets. Along the c axis, the N-N bond center approaches the phenyl-ring centroids of its neighbouring molecules above and below to giveoverlap (at a distance of ca 3.57 Å ), thus fusing the molecules into a threedimensional framework.

Comment
Phenylhydrazone and its derivatives show remarkable stability and high tendency to form non-centrosymmetric crystal packing (Lewis et al., 1999;Mague et al., 1997) and exceptional electronic, bioactive and chemical properties useful for analytic purposes (Mahy et al., 1993), for biological chemistry (Thami et al., 1992) and also for optical materials (Serbutoviez et al., 1995). As a part of our ongoing research (Liu et al., 2007;Liu et al., 2008), the crystal structure of the title compound was solved.
The molecule of the title compound exists in the (E)-isomer configuration, not as the generally more stable (Z)-isomer (Schemes 1 and 2). The (E)-isomer exists here because of the N-H···O intra-molecular hydrogen bond stabilizes it by forming a pseudo-ring S(6) (Bernstein et al., 1995) Table 1 and 2). The N1-C6 bond distance at 1.397 (3) Å is longer than the expected C═N double bond (1.32 Å) but is shorter than a C-N single bond (1.47 Å) because of the classic sp 2 -hybrid nitrogen atom, as also found in our earlier work (Liu et al., 2007(Liu et al., , 2008. All these effects may help all non-hydrogen atoms to form a perfect plane which coincides with the mirror plane of the space group, less for the hydrogen atoms of the two methyl groups whose six H atoms are disordered over two orientations. In the crystal packing the molecules are linked into larger perfectly planar sheets via by four C-H···O inter-molecular hydrogen bonds and one N-H···O intra-molecular hydrogen bond running parallel to the [001] plane (Fig. 2, Table 2). H1 atom of the N1 atom is a part of a bifurcated system and makes both intra-and intermolecular H-bridges, with angles around the H1 adding up to 360°. Finally, along the c axis the N1-N2 bond centers of molecules combine its up and down neighbours' phenyl rings into three dimensional framework (Fig. 2). Consecutive bond centers···phenyl ring centers are at a distance of ca. 3.57 Å and an incline at an angle of ca. 137° (Fig. 3).

Experimental
The title compound was synthesized according to literature procedure (Wang et al. 2005;Liu et al. 2008). Crystals suitable for X-ray diffraction were obtained by slow evaporation of a solution of the solid in dichloromethane at room temperature over a period of 6 d.

Refinement
After their location in a difference map, all H atoms were fixed geometrically at ideal positions and allowed to ride on the parent C atoms, with C-H distances of 0.93 (aromatic) or 0.97 Å (methyl), and with U iso (H) values of 1.2U eq (C, N).
supplementary materials sup-2 Figures   Fig. 1. The molecular structure of the title compound, showing 30% probability displacement ellipsoids. Disorder of the two methyl groups are indicated and the N-H···O intra-molecular hydrogen bond shown as dashed lines.