1-Chloro-1-[(Z)-2-phenylhydrazin-1-ylidene]propan-2-one

The title compound, C9H9ClN2O, is close to planar (r.m.s. deviation for the non-H atoms = 0.0446 Å); it exists in a cis conformation with respect to the C=N double bond. In the crystal, the ketone O atom accepts both N—H⋯O and C—H⋯O hydrogen bonds, which leads to [010] infinite chains incorporating R 2 1(6) loops. The crystal structure also features a C—H⋯π interaction.

The title compound, C 9 H 9 ClN 2 O, is close to planar (r.m.s. deviation for the non-H atoms = 0.0446 Å ); it exists in a cis conformation with respect to the C N double bond. In the crystal, the ketone O atom accepts both N-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds, which leads to [010] infinite chains incorporating R 2 1 (6) loops. The crystal structure also features a C-HÁ Á Á interaction.

D-HÁ
Data collection: APEX2 (Bruker, 2009); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009  The asymmetric unit of the title compound is shown in Fig. 1. All of the non-H atoms lie nearly on a plane with r.m.s. deviation of 0.0446 Å. The molecule exists in cis configuration with respect to the C7═N2 double bond. Bond lengths and angles are comparable to those in related structures (Asiri et al., 2011a,b).

Experimental
The title compound was prepared by the coupling reaction of 3-chloro-2,4-pentanedione and the diazonium salt of aniline at 0-5 °C (Dieckmann & Platz, 1905). Yellow blocks were recrystallised from ethanol solution.

Refinement
The atom H1N1 was located in a difference fourier map and refined freely [N1-H1N1 = 1.00 (3) (011) were omitted in the final refinement.

Special details
Experimental. The crystal was placed in the cold stream of an Oxford Cryosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K. 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.