1-Acetyl-5-ferrocenyl-3-phenyl-2-pyrazoline

In the title compound, [Fe(C5H5)(C16H15N2O)], the pyrazoline ring and the phenyl ring are nearly coplanar, making a dihedral angle of 6.54 (2)°, while the substituted cyclopentadienyl ring is twisted out of the pyrazoline ring plane by 81.32 (1)°. The molecules in the crystal structure are held together by weak C—H⋯O intermolecular hydrogen bonds and two C—H⋯π interactions.

In the title compound, [Fe(C 5 H 5 )(C 16 H 15 N 2 O)], the pyrazoline ring and the phenyl ring are nearly coplanar, making a dihedral angle of 6.54 (2) , while the substituted cyclopentadienyl ring is twisted out of the pyrazoline ring plane by 81.32 (1) . The molecules in the crystal structure are held together by weak C-HÁ Á ÁO intermolecular hydrogen bonds and two C-HÁ Á Á interactions.

Comment
Pyrazolines are well known nitrogen-containing five-membered heterocyclic compounds. Condensation of nitrogen-containing binucleophilic agents with α, β unsaturated ketones is one of the most suitable synthetic pathways for 2-pyrazolines (Kudar et al., 2005), which possess widespread pharmaceutical properties such as antimicrobial (Küçükgüzel et al., 2000), anticonvulsant (Karthikeyan et al., 2007, antidepressant (Özdemir et al., 2007), antiandrogenic (Amr et al., 2006), antifungal and anti-inflammatory (Guirado et al., 2004) activities. Furthermore, N-acetylated 2-pyrazolines are inhibitors of kinesin spindle protein (KSP); potentially useful for the treatment cancer (Johnson et al., 2007). Metallocenes are also known to exhibit a wide range of biological activity. Among them ferrocenyl compounds display interesting antibacterial (Fouda et al., 2007), antitumor (Jaouen et al., 2004), antimalarial and antifungal (Biot et al., 2004) activities. Therefore, incorporation of a ferrocene fragment into a heterocyclic ring may enhance their biological activities or generate new medicinal properties (Fang et al., 2003). As a part of an ongoing investigation of the chemistry of ferrocenyl pyrazolines, the title compound (I) was synthesized and its crystal structure was determined.
The molecular structure of the title compound is shown in Fig. 1. The dihedral angle of 6.54 (2)° between pyrazoline ring and the phenyl ring indicates that they are conjugated with each other; this is accord with the C1-C7 bond [1.474 (3)  The Fe-Cg s and Fe-Cg as distances are 1.6454 (13)Å and 1.6510 (15) Å, respectively, and the Cg s -Fe-Cg as angle is 178.90 (8)°, where Cg s and Cg as are the centroids of the substituted and unsubstituted Cp rings. The small dihedral angle of 3.2963 (2)° between the unsubstituted and substituted Cp rings exposes that the two Cp rings are parallel to each other. The average C12-Cg s -Cg as -C20 torsion angle of 4.789 (2)° brings that the two Cp rings of the ferrocenyl group is nearly in an eclipsed conformation.
The pyrazoline ring and substituted Cp ring make a dihedral angle of 81.32 (1)°. The dihedral angle between the phenyl ring and substituted Cp ring is 75.82 (1)°, whereas the phenyl ring plane deviates from the unsubstituted Cp ring with an angle of 76.60 (1)°. The molecules in the crystal held together by two weak intermolecular C5-H5···O1 and C16-H16···O1 hydrogen bonds and two C-H···π interactions (Table 1, Fig. 2).

Experimental
A mixture of 3-ferrocenyl-1-phenyl-propen-2-one (0.32 mmol, 0.1 g), 80% hydrazine monohydrate (7.04 mmol, 0.45 g) and glacial acetic acid (10 ml) was refluxed under nitrogen atmosphere for 4 h. TLC indicated the formation of the reaction product. It was poured into ice-water to give orange solid. The participate was separated by filtration and washed with water.
The solid product was dried at room temperature. Single crystals of the title compound suitable for X-ray measurements

Refinement
All C-H atoms were refined using the riding model approximation, with C-H = 0.93-0.98Å [U iso (H) = 1.2 or 1.5U eq (C)]. Fig. 1. A view of (I), with the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability.

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 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.