Comment

The Cambridge Crystallographic Data Centre `Blind Structure Prediction Tests' are carried out periodically by a number of participating groups in order to evaluate developments in structure prediction techniques. As part of the preparations for the 2004 test, five well crystalline samples whose crystal structure was previously unknown were provided by Professor Angelo Gavezzotti. The materials were from a collection of nitrotoluene derivatives synthesized by Wilhelm Koerner about a century ago and retrieved from a depository at the University of Milan. The structures and analyses of several other materials from this collection have recently been discussed (Demartin et al., 2004).

The sample consisted of a mixture of crushed and broken fragments and some glass-clear pale yellow lath-shaped crystals. These were always long, and generally very thin. Attempts were made to obtain a roughly isometric sample, but the specimens inevitably cleaved freely parallel to their long length if any attempt was made to cut them into shorter lengths. Full data sets were collected for three samples [(1) 0.02 × 0.22 × 0.48 mm, 0.0021 mm³; (2) 0.04 × 0.06 × 2.0 mm, 0.0048 mm³; and (3) 0.04 × 0.15 × 0.83 mm, 0.0049 mm³]. The first two samples were collected at 190 K and refined to R(all data) of 7.99 and 7.44%. The third sample was measured at 150 K and refined to 4.25%. Comparison of the atomic parameters for the first (smallest crystal) and third (most isometric crystal; Fig. 1) refinements had a mean atomic discrepancy of 0.0018 Å and an r.m.s. atomic discrepancy of 0.008 Å for the non-H atoms. The discrepancies between the U_eq values were larger, but probably not strictly comparable because of the temperature differences. The computed absorption corrections for the third sample perpendicular to the long axis are insignificant; it is presumed that the minimum and maximum scale factors reported by the multiscan calculation (SCALEPACK) are due to changes in illuminated volume (Görbitz, 1999). The results reported here are for the third sample only.

As reported by Demartin et al. (2004), the nitro groups are not coplanar with the benzene ring (Fig. 2). Those authors found that the torsion angles for a nitro group adjacent to another nitro group on one side and an H atom on the other fall in the interval 27-41°. In this case, the torsion angles are C1-C2-N12-O14 = 22.87 (19)° and C2-C1-N15-O17 = 52.08 (18)°. The acetamide group is itself almost planar [C10-C8-N7-C5 = 173.10 (12)°], but also inclined to the benzene ring [C6-C5-N7-C8 = -41.46 (19)°]. Hydrogen bonding between atom H71 of one molecule and O9 of an adjacent molecule causes the structure to consist of chains parallel to the b axis (Fig. 3). The benzene rings lie parallel to each other other with a perpendicular separation of 3.58 Å (Fig. 4). Other intermolecular contacts are unexceptional.

Figure 1 Perspective views of the crystal of (3), showing indices of principal faces and their relationship to the diffractometer axes.

Figure 2 The molecule of the title compound, with displacement ellipsoids drawn at the 50% probability level. H-atom radii are proportional to Uiso.

Figure 3 Packing diagram of the title compound, viewed parallel to the a axis, showing the hydrogen bonding as dashed lines.

Figure 4 Part of the packing of the title compound, showing the parallel stacking of the benzene rings. The dashed line indicates a hydrogen bond.

Experimental

Crystals were obtained by slow evaporation of an ethanol solution

Crystal data

C9H9N3O5 Mr = 239.19 Monoclinic, P21/n a = 12.5693 (4) Å b = 4.8531 (1) Å c = 17.2663 (5) Å = 99.1624 (15)° V = 1039.81 (5) Å3 Z = 4 Dx = 1.528 Mg m-3 Mo K radiation Cell parameters from 2364 reflections = 5-27° = 0.13 mm-1 T = 150 K Lath, pale yellow 0.83 × 0.15 × 0.04 mm

Data collection

Nonius KappaCCD diffractometer scans Absorption correction: multi-scan DENZO/SCALEPACK (Otwinowski & Minor, 1997) Tmin = 0.61, Tmax = 0.99 4326 measured reflections 2357 independent reflections 2356 reflections with I > 3(I) Rint = 0.035 max = 27.5° h = -16 16 k = -6 5 l = -22 22

Refinement

Refinement on F2 R[F2 > 2(F2)]= 0.051 wR(F2) = 0.095 S = 1.00 2356 reflections 182 parameters Only coordinates of H atoms refined w = 1/[2(F2) + 0.04 + 0.35p] where p = [max(Fo2,0) + 2Fc2]/3 (/)max = 0.001 max = 0.37 e Å-3 min = -0.31 e Å-3 Extinction correction: Larson (1970) Extinction coefficient: 140 (20)

Table 1 Selected geometric parameters (Å, °) C1-C2 1.3958 (18) C1-C6 1.3723 (19) C1-N15 1.4716 (17) C2-C3 1.3812 (19) C2-N12 1.4597 (17) C3-C4 1.3961 (19) C4-C5 1.4008 (18) C4-C11 1.5029 (19) C5-C6 1.3976 (19) C5-N7 1.4075 (17) N7-C8 1.3638 (18) C8-O9 1.2222 (18) C8-C10 1.500 (2) N12-O13 1.2313 (15) N12-O14 1.2273 (16) N15-O16 1.2216 (15) N15-O17 1.2202 (15) C2-C1-C6 120.39 (12) C2-C1-N15 122.09 (12) C6-C1-N15 117.28 (11) C1-C2-C3 119.86 (12) C1-C2-N12 121.60 (12) C3-C2-N12 118.32 (11) C2-C3-C4 120.96 (12) C3-C4-C5 118.30 (12) C3-C4-C11 119.68 (12) C5-C4-C11 122.01 (12) C4-C5-C6 120.78 (12) C4-C5-N7 119.76 (12) C6-C5-N7 119.43 (11) C5-C6-C1 119.70 (12) C5-N7-C8 124.40 (12) N7-C8-O9 121.95 (13) N7-C8-C10 115.49 (12) O9-C8-C10 122.56 (13) C2-N12-O13 118.02 (11) C2-N12-O14 117.94 (11) O13-N12-O14 124.00 (12) C1-N15-O16 117.18 (11) C1-N15-O17 117.65 (11) O16-N15-O17 125.09 (12)

Table 2 Hydrogen-bonding geometry (Å, °) D-HA D-H HA DA D-HA N7-H71O9i 0.868 (19) 2.002 (19) 2.8632 (17) 171.2 (15) Symmetry code: (i) x,y-1,z.

All H atoms were seen in the difference electron-density map. Their positions and isotropic displacement parameters were regularized by several cycles of refinement using slack restraints, after which the refinement was completed using riding constraints. Reflection ,3,10 was omitted from the final refinement.

Data collection: COLLECT (Nonius, 1997-2001); cell refinement: DENZO/SCALEPACK (Otwinowski & Minor, 1997); data reduction: DENZO/SCALEPACK; program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: CRYSTALS (Betteridge et al., 2003); molecular graphics: CAMERON (Watkin et al., 1996); software used to prepare material for publication: CRYSTALS.