4-Chloro-N′-[(3Z)-2-oxo-2,3-dihydro-1H-indol-3-ylidene]benzohydrazide

In the title compound, C15H10ClN3O2, the benzene ring is slightly twisted out of the plane of the 2,3-dihydro-1H-indole ring system (r.m.s. deviation = 0.007 Å), forming a dihedral angle of 7.4 (3)°. An intramolecular N—H⋯O hydrogen bond forms a six-membered ring. In the crystal, molecules are linked via N—H⋯O and C—H⋯O hydrogen bonds, forming layers alternately perpendicular to [011] and [0-11].

In the title compound, Fig. 1, the intramolecular N1-H1···O2 hydrogen bond forms a pseudo-six-membered ring. The nine non-H ring atoms of the fused five-and six-membered ring system are almost coplanar (r.m.s. deviation = 0.007 Å).
In the crystal structure, molecular layers formed by N-H···O and C-H···O hydrogen bonds are alternately perpendicular to [011] and to [0-11] directions (Table 1 and Fig. 2).

Experimental
A mixture of 1 mmol (170.6 mg) 4-chlorobenzohydrazidean and 1 mmol (147 mg) 1H-indole-2,3-dione in 25 ml ethanol with few drops of glacial acetic acid was refluxed for 5h. The solid formed was collected and recrystallized from DMF to furnish the title compound as yellow crystals suitable for X-ray analysis [M.p. 558 K].

Refinement
The NH H atoms (H1 on N1) was located in a difference Fourier map and refined with a distance restraint: N1-H1 = 0.90 (5) Å with U iso (H) = 1.2U eq (N). The remaining H atoms were placed in calculated positions and refined using a riding model approximation: C-H = 0.95 Å and N-H = 0.91 Å with U iso (H) = 1.2U eq (C, N). The small proportion of reflections observed is a result of the rather poor quality of the very thin crystals obtained.

Figure 2
A view along the b axis of the crystal packing of the title compound. The hydrogen bonds are shown as a dashed lines (see Table 1 for details). where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.30 e Å −3 Δρ min = −0.37 e Å −3 Absolute structure: Flack (1983), 478 Friedal pairs (44% coverage) Absolute structure parameter: −0.06 (5) 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 e.s.d.'s 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 > σ(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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Cl1 −0.02432 (