3-(2-Ethyl-2-phenylhydrazin-1-ylidene)indolin-2-one

In the title compound, C16H15N3O, the dihedral angle between the indole ring system (r.m.s. deviation = 0.020 Å) and the phenyl ring is 14.49 (9)°. The molecular conformation is supported by an intramolecular C—H⋯O interaction, which closes an S(7) ring. In the crystal, inversion dimers linked by pairs of N—H⋯O hydrogen bonds generate R 2 2(8) loops.

In the title compound, C 16 H 15 N 3 O, the dihedral angle between the indole ring system (r.m.s. deviation = 0.020 Å ) and the phenyl ring is 14.49 (9) . The molecular conformation is supported by an intramolecular C-HÁ Á ÁO interaction, which closes an S(7) ring. In the crystal, inversion dimers linked by pairs of N-HÁ Á ÁO hydrogen bonds generate R 2 2 (8) loops.
The title compound, C 16 H 15 N 3 O is an structural analogue of our previously published compound 3-amino-N′-(2oxoindolin-3-ylidene)-benzohydrazide (Jamal et al., 2011) with the difference that the keto amine phenyl moiety is replaced by phenyl ring (C9-C14) and N3 is substituted with ethyl group (C15-C16). The phenyl and indole rings are each planar with the dihedral angle of 14.49 (9)° between them. The geometry of molecule is stabilized by an intramolecular C15-H15A···O1 hydrogen bond. In the crystal molecules are consolidated by intermolecular N1-H1A···O1 hydrogen bond ( Fig. 2. symmetry codes as in Table 2).

Experimental
To a solution of 2,3-Indolinedione (10 mmol, 1.47 g) in 15 ml of ethanol with few drops of glacial acetic acid and 1ethyl-1-phenylhydrazine (10 mmol,1.36 g) in 15 ml e thanol were added. The mixture was refluxed for 24 h and a solid was obtained upon removal of the solvent by rotary evaporation.The resulting solid was washed with hexane to afford the title compound. Yellow plates were grown from a mixture of ethanol and methanol (1:1) solvents by slow evaporation at room temperature.

Refinement
H atoms on methyl, methylene, phenyl and nitrogen were positioned geometrically with C-H = 0.96, 0.97, 0.93 and C-H = 0.86 Å respectively, and constrained to ride on their parent atoms with U iso (H)= 1.2U eq (CH, CH 2 and NH) and 1.5U eq (CH 3 ).

3-(2-Ethyl-2-phenylhydrazin-1-ylidene)indolin-2-one
Crystal data where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.18 e Å −3 Δρ min = −0.17 e Å −3 Special details Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'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 > 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.