(2Z)-N-(2-Chlorobenzyl)-2-(2-oxo-2,3-dihydro-1H-indol-3-ylidene)hydrazinecarbothioamide

In the title compound, C16H13ClN4OS, the isatin ring system is oriented at dihedral angles of 10.60 (7) and 72.60 (3)° with respect to the thiosemicarbazide and 2-chlorobenzyl groups, respectively. The near planarity of the isatin and thiosemicarbazide groups [r.m.s. deviations of 0.0420 and 0.0163 Å, respectively] is reinforced by intramolecular N—H⋯O and N—H⋯N hydrogen bonds, which generate S(6) and S(5) rings, respectively. In the crystal, inversion dimers linked by pairs of N—H⋯O hydrogen bonds generate R 2 2(8) loops. Aromatic π–π stacking interactions between the centroids of heterocyclic five-membered and benzene rings [distance = 3.6866 (11) Å] are also observed.

In the title compound, C 16 H 13 ClN 4 OS, the isatin ring system is oriented at dihedral angles of 10.60 (7) and 72.60 (3) with respect to the thiosemicarbazide and 2-chlorobenzyl groups, respectively. The near planarity of the isatin and thiosemicarbazide groups [r.m.s. deviations of 0.0420 and 0.0163 Å , respectively] is reinforced by intramolecular N-HÁ Á ÁO and N-HÁ Á ÁN hydrogen bonds, which generate S(6) and S(5) rings, respectively. In the crystal, inversion dimers linked by pairs of N-HÁ Á ÁO hydrogen bonds generate R 2 2 (8) loops. Aromaticstacking interactions between the centroids of heterocyclic five-membered and benzene rings [distance = 3.6866 (11) Å ] are also observed.

Experimental
To a hot solution of isatin (0.74 g, 5 mmol) in 50% aqueous ethanol (15 ml) was added 4-(2-chlorobenzyl)thiosemicarbazide (1.08 g, 5 mmol) dissolved in ethanol (10 ml) under stirring. The reaction mixture was then refluxed for 2 h. The orange crystalline solid formed during heating was collected by suction filtration. Thorough washing with hot aqueous ethanol afforded the title compound in pure form (1.55 g, 90%), m.p. 525 K. The orange prisms of title compound were grown from chloroform solution by slow evaporation of the solvent.

Refinement
The H-atoms were positioned geometrically at C-H = 0.93 Å and N-H = 0.86 Å, respectively and included in the refinement as riding with U iso (H) = xU eq (C, N), where x = 1.2 for all H-atoms.  View of the title compound with displacement ellipsoids drawn at the 50% probability level. The dotted lines represent the intramolecular hydrogen bonds.

Figure 2
The partial packing diagram, which shows that molecules form dimers with R 2 2 (8) ring motifs.

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 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Cl1 0.34601 (5