Crystal structure of (4Z)-4-{[(2-chlorophenyl)amino](furan-2-yl)methylidene}-3-methyl-1-phenyl-4,5-dihydro-1H-pyrazol-5-one

In the title compound, C21H16ClN3O2, the pyrazolone ring and the O=C—C=C—N mean plane [maximum deviation = 0.022 (2) Å] are nearly coplanar, making a dihedral angle 4.56 (8)°, while the phenyl and pyrazole rings subtend a dihedral angle of 19.75 (8)°. The compound is in the enamine–keto form and its structure is stabilized by an intramolecular N—H⋯O hydrogen bond. In the crystal, molecules are linked via C—H⋯N hydrogen bonds, forming chains along [010]. Between the chains there are π–π interactions [inter-centroid distances = 3.3902 (9) and 3.5956 (11) Å], linking the chains to form sheets parallel to (10-1).

significant scientific and applied interest in biological, analytic applications, catalysis, dye and extraction metallurgy (Raman et al., 2001;Casas, et al., 2007). 1-phenyl-3-methyl-4-(2-furoyl)-5-pyrazolone (HPMFP), is a member of a family of 4-heterocyclic acylpyrazolones, first synthesized in 1983 (Dong et al., 1983). In recent years, we have reported on Schiff bases derived from HPMFP and their complexes, which possess high antibacterial activity (Li et al., 2000;Zhang et al., 2008). In order to further investigate the coordination abilities and the behaviour of pyrazolone based ligands, we extended the study to the syntheses of new title pyrazolone derivative, and report herein on its crystal structure.
The molecular structure of the title compound is shown in Fig. 1. The phenyl ring (C1-C6) is twisted by 19.75 (4)° with respect to a plane defined by the pyrazole ring (N1/N2/C7-C9). The pyrazole ring and the (O1/C7/C8/C11/N3) mean plane [maximum deviation = 0.022 (2) Å for atom C7] are nearly coplanar with a dihedral angle 4.56 (8) °. The bond length C8═C11 (1.384 (2) Å) lies between the usual C-C and C═C bond lengths and indicates the delocalization of the electrons because of the addition of a proton to atom N3 which is more favorable than to O1, as shown in the difference Fourier map. Atoms O1 and N3 are on the same side of the C8═C11 bond, hence available for complexation with metals.
All bond lengths and angles are normal and comparable with those found for related compounds (Zhang et al., 2007;Li et al., 2009).
In the crystal, molecules are linked via C-H···N hydrogen bonds forming chains along [010]; see Table 1 and Fig. 2.

S2. Experimental
The starting compound HPMFP was synthesized according to the method proposed by Jensen (1959). A mixture of a 10 ml HPMFP (2 mmol, 0.5366 g) anhydrous ethanol solution, and a 0.21 ml of an o-chloroaniline (2 mmol, 0.2545 g) solution was refluxed for ca. 5 h, adding a few drops of glacial acetic acid as a catalyst. Then ethanol was removed by evaporation and the resulting black precipitate formed was filtered off, washed with cold anhydrous ethanol and dried in air. Yellow block-like crystals were obtained by slow evaporation of a solution in anhydrous ethanol at room temperature after a few days.

S3. Refinement
The H atom bonded to N3 was located in a difference Fourier map and freely refined. The C-bound H atoms were placed in calculated positions and refined as riding: C-H = 0.93 -0.97 Å with U iso (H) = 1.5 eq U(C) for methyl H atoms and = 1.2 eq (C) for other H atoms.

Figure 1
The molecular structure of the title compound, with atom labelling. Displacement ellipsoids are drawn at 30% probability level.

Figure 2
A perspective view along the b axis of the crystal packing of the title compound. The hydrogen bonds are shown as dashed lines (see Table 1 for details; H atoms not involved in hydrogen bonding have been omitted for clarity). where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.30 e Å −3 Δρ min = −0.33 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.