1,5-Dimethyl-4-{[(3-methyl-5-oxo-1-phenyl-4,5-dihydro-1H-pyrazol-4-ylidene)(thiophen-2-yl)methyl]amino}-2-phenyl-1H-pyrazol-3(2H)-one

In the title compound, C26H23N5O2S, an intramolecular N—H⋯O interaction generates an S(6) ring. The essentially planar S(6) and pyrazole rings [maximum deviations = −0.0270 (14) and 0.0195 (15) Å, respectively] are nearly coplanar, making a dihedral angle of 3.94 (6)°. The S(6) ring makes dihedral angles of 23.79 (6), 78.53 (6) and 67.91 (6)° with the pyrazolone ring, the pyrazole ring and the benzene ring of antipyrine, respectively. The structure exhibits a thienyl-ring flip disorder with occupancy factors in the ratio 0.82:0.18.


Comment
Pyrazolones form a very important class of heterocycles due to their properties and applications (Casas et al., 2007). Schiffbases derived from 1-phenyl-3-methyl-4-acyl-5-pyrazolone have found extensive application in coordination chemistry (Shi et al., 2005)and in antibacterial activation (Zhang et al., 2008;Li et al., 2000). In continuation of our studies on pyrazolone schiff bases (Zhu et al., 2010a,b), we herein report the crystal structure of the title pyrazole compound.
The molecular structure of the title compound is shown in Fig. 1. An intramolecular N-H···O interaction generates a six-membered ring, producing an S(6) ring (O2 N3 C12 C17 C18), which stablizing the enamine-keto form of the compound. The S(6) ring and pyrazole ring (N4 N5 C17 C18 C19) are essentially planar,with the maximum deviations of -0.0270 (14) and 0.0195 (15) Å, respectively, at atoms C12 and C17.The two rings are coplanar to one another, as indicated by the dihedral angle formed between them of 3.94 (6)°. The S(6) ring makes dihedral angles of 23.79 (6)°,78.53 (6)° and 67.91 (6)° with the benzene ring of pyrazolone, the pyrazole ring and benzene ring of antipyrine,respectively. The bond lengths and angles agree well with those closely related pyrazole structures (Goh et al., 2009) The structure exhibits a thienyl-ring flip disorder with the occupancy factors in the ratio 82/18.

Experimental
The title compound was synthesized by refluxing the mixture of 1-phenyl-3-methyl-4-(2-thenoyl)pyrazolone-5 (HPMTP) (15m mol) and 4-antipyrine (15m mol) in ethanol (100 ml) over a steam bath for about 4 h, then the solution was cooled down to room temperature. After seven days, pale yellow block was obtained and dried in air. The product was recrystallized from ethanol which afforded pale yellow and acerate crystals suitable for X-ray analysis.

Refinement
During refinement, the thienyl ring showed evidence of ring-flip disorder which is common for unsubstituted 2-and 3-thienyl rings (Crundwell et al., 2003). After finding three of the flipped disordered atoms in the difference map, the rest of the ring was generated and modeled. The occupancy factors of the disordered thienyl ring were first refine restraining the sum of the occupancy factore to be equal to 1.0. Once stabilised, the occupancy factors were fixed and not refined anymore. The final model suggested that the thienyl ring disorder was in the ratio 82/18. The disordered model was refined using the tools available in SHELXL-97 (Sheldrick, 2008): SADI for restraining distances, FLAT for constraining the thienyl rings to be planar, EXYZ for linking atoms occupying the same site and EADP to correlate anisotropic thermal parameters for related disordered atoms.
All H atoms were geometrically positioned and treated as riding on their parent atoms, with C-H = 0.93 Å for the aromatic, 0.96 Å for the methyl and N-H= 0.86 Å with U iso (H)= 1.2 U eq (Caromatic, N) or, 1.5U eq (Cmethyl).  Fig. 1. The molecular structure of the title compound with the atom numbering scheme. Displacement ellipsoids are drawn at the 30% probability level. H atoms are presented as a small spheres of arbitrary radii. Only the major component of the disordered thienyl ring is represented for the sake of clarity.

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