1-( 3-Chloro-6-nitro-1 H-indazol-1-yl ) ethan-1-one

The asymmetric unit of the title compound, C9H6ClN3O3, contains one full molecule in a general position and a half molcule sitting on a crystallographic mirror plane. In the crystal, molecules form stacks extending along the b-axis direction through a combination of offset – stacking between indazole units and C—Cl (ring) interactions with the six-membered rings of the same units. Elaboration of the C—Cl (ring) interactions along the a-axis direction forms slabs of molecules parallel to [001]. The stacks are joined by a combination of C—H O and C—H N hydrogen bonds.


Structure description
Studies of the structure and physicochemical properties of the indazole ring have been reviewed (Abbassi et al., 2014;Li et al., 2003;Lee et al., 2001). Indazole is a frequently found motif in drug substances with important biological activities, such as antimicrobial (Patel et al., 1999) and anti-inflammatory activities (Lin et al., 2008), and anticancer effects (Zhu et al., 2007). As a continuation of our studies of indazole derivatives (Mohamed Abdelahi et al., 2017a,b,c), we report the synthesis and structure of the title compound (Fig. 1).
The asymmetric unit of the title compound consists of one molecule in a general position and a half molecule located on a crystallographic mirror plane at y = 1/4. The indazole portion of the former is planar to within 0.007 (1) Å (C16) and the dihedral angle between its mean plane and the mirror on which the latter lies is 4.82 (3) Å . For the overlay of the two independent molecules, values of 0.0130 and 0.0288 Å are obtained, respectively, for the r.m.s. deviation and the maximum deviation. In the crystal, molecules form stacks extending along the b-axis direction. One element of the stack is a dimer formed by pairwise head-to-tail offsetstacking interactions between the indazole data reports portions of two molecules sitting on general positions [ Fig. 2; Cg4Á Á ÁCg5 iii = 3.6023 (8) Å ]. The dimers are connected across the crystallographic mirror plane by complementary C10-Cl2Á Á Á(Cg2) and C1-Cl1Á Á Á(Cg5) interactions with the molecule sitting on the mirror [ Fig. 2; Cl1Á Á ÁCg5 i = 3.2306 (6) Å , C1Á Á ÁCg5 i = 3.748 (1) Å and C1-Cl1Á Á ÁCg5 i = 95.13 (5) ; Cl2 i Á Á ÁCg2 = 3.4284 (6) Å , C10 i Á Á ÁCg2 = 3.4284 (4) Å and C10 i -Cl2 i Á Á ÁCg2 = 91.73 (5) ]. Elaboration of the C10-Cl2Á Á Á(Cg2) and C1-Cl1Á Á Á(Cg5) interactions along the a-axis direction forms slabs of molecules parallel to [001]. The stacks are joined by a combination of C-HÁ Á ÁO and C-HÁ Á ÁN hydrogen bonds, as well as short ClÁ Á ÁO contacts of 2.964 (2) and 2.982 (1) Å with the nitro groups of neighbouring molecules (Table 1 and Fig. 4). As shown in Fig. 3, an R 3 3 (19) graph set is formed by two C-HÁ Á ÁO hydrogen bonds and one ClÁ Á ÁO interaction for the molecule in the general position. A corresponding set is formed with the molecule in the special position.

Figure 1
The asymmetric unit of the title compound, with the atom-labelling scheme and 50% probability ellipsoids.

Figure 3
Detail of the R 3 3 (19) graph set formed by the Cl1Á Á ÁO3 interaction and two C4-H4Á Á ÁO1 hydrogen bonds. Genreic atom labels without symmetry codes have been used.

Figure 4
Packing viewed along the a-axis direction, showing the layer structure. The -stacking and C-ClÁ Á Á(ring) interactions (omitted for clarity) run along the b-axis direction. under reflux for 24 h. After completion of the reaction (monitored by thin-layer chromatography), the solvent was removed under vacuum. The residue obtained was recrystallized from ethanol to afford the title compound as colourless crystals (yield 75%).

Refinement
Crystal and refinement details are presented in Table 2.

Special details
Experimental. The diffraction data were obtained from 3 sets of 400 frames, each of width 0.5° in ω, colllected at φ = 0.00, 90.00 and 180.00° and 2 sets of 800 frames, each of width 0.45° in φ, collected at ω = -30.00 and 210.00°. The scan time was 25 sec/frame.

data-2
IUCrData (2017). 2, x171202 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 > 2sigma(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.