N′-[Bis(benzylsulfanyl)methylidene]benzohydrazide

In the title hydrazonodithioate, C21H19N3OS2, the amide group is twisted out of the plane through the S2C=N atoms: the C—N—N—C torsion angle is 139.71 (13)°. The pyridine ring forms dihedral angles of 52.96 (8) and 86.46 (8)° with the phenyl rings, and the latter are approximately orthogonal [dihedral angle = 76.42 (9)°]. Supramolecular chains sustained by N—H⋯O hydrogen bonds and propagated by glide symmetry along the c axis are found in the crystal structure. The chains are consolidated into a three-dimensional architecture by C—H⋯O and C—H⋯N interactions.

In the title hydrazonodithioate, C 21 H 19 N 3 OS 2 , the amide group is twisted out of the plane through the S 2 C N atoms: the C-N-N-C torsion angle is 139.71 (13) . The pyridine ring forms dihedral angles of 52.96 (8) and 86.46 (8) with the phenyl rings, and the latter are approximately orthogonal [dihedral angle = 76.42 (9) ]. Supramolecular chains sustained by N-HÁ Á ÁO hydrogen bonds and propagated by glide symmetry along the c axis are found in the crystal structure. The chains are consolidated into a three-dimensional architecture by C-HÁ Á ÁO and C-HÁ Á ÁN interactions.

Crouse and Edward R. T. Tiekink Comment
Our interest in investigating the coordination properties of ligands containing the H-N-C═S moiety (Tarafder et al., 2002;Ravoof et al., 2010) and our desire to expand the study of this class of biologically important compounds has lead us to synthesize a series of related ligands (Ali et al., 2001;Manan et al., 2012). The title compound N′-bis(benzylsulfanyl)methylidene]benzohydrazide, (I), was obtained from an attempt to prepare S-benzyl isonicotinoylcarbonohydrazonodithioate (see Experimental).
In (I), Fig. 1, the amide is twisted out of the plane through the S 2 C═N atoms with the C1-N1-N2-C16 torsion angle being 139.71 (13)°. A similar twist was found in the structure of (PhCH 2 S) 2 C═ NN(H)C(═ O)C 6 H 4 OMe-4 (Jasinski et al., 2010) but a planar arrangement was observed in the structure of (PhCH 2 S) 2 C═NN(H)C(═O)C 6 H 4 OMe-2 (Singh et al., 2007). The dihedral angle between the phenyl rings is 76.42 (9)°, indicating an almost orthogonal relationship. Each of these rings forms a dihedral angle of 52.96 (8) and 86.46 (8)° with the pyridyl ring.
The crystal packing features supramolecular chains sustained by N-H···O hydrogen bonds, Table 1, and propagated by glide symmetry along the c axis, Fig. 2. Chains are consolidated into a three-dimensional architecture by C-H···O and C -H···N interactions, Fig. 3 and Table 1.

Experimental
The procedure to synthesize S-benzyldithiocarbazate (Ali & Tarafder, 1977) was adapted to prepare S-benzyl isonicotinoylcarbonohydrazono dithioate by replacing hydrazine with its isonicotinic acid derivative. Potassium hydroxide (0.2 mol, 11.2 g) in absolute ethanol (70 ml) was added to a suspension of isonicotinic acid hydrazide (0.2 mol, 27.43 g) in absolute ethanol (700 ml). The pale-yellow solution was kept in an ice-salt bath and carbon disulfide (0.2 mol) was added drop-wise with constant stirring over one hour. Benzylchloride (0.2 mol, 23 ml) was then added drop-wise with vigorous stirring to the pale-orange solution obtained above. The reaction temperature was maintained below 278 K.
An unidentified pale-yellow solid (33.84 g) which did not contain any benzyl substituent was filtered from the mixture.
The filtrate was kept in a freezer for one week before it was used as replacement for absolute ethanol to repeat the above reaction. The final solution produced dark-yellow blocks of the title compound after storage at 268 K for 5 months.

Refinement
Carbon-bound H-atoms were placed in calculated positions (C-H = 0.95 to 0.99 Å) and were included in the refinement in the riding model approximation with U iso (H) set to 1.2U equiv (C). The amino H-atom was refined with a distance restraint of N-H = 0.88±0.01 Å, and with U iso (H) = 1.2U eq (N).

Figure 1
The molecular structure of (I) showing displacement ellipsoids at the 50% probability level.

Special details
Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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 > 2σ(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.