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The mol­ecular skeleton of the title compound, C11H9F3N4O2, is almost planar and exhibits a polarized (charge-separated) electronic structure in the nitro­aniline portion. Mol­ecules are linked by N-H...N and C-H...O hydrogen bonds to form a chain in which centrosymmetric R22(6) and R22(16) rings alternate.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270113000607/yf3024sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270113000607/yf3024Isup2.hkl
Contains datablock I

CCDC reference: 925771

Comment top

We report here the molecular and supramolecular structure of 5-methyl-N-[2-nitro-4-(trifluoromethyl)phenyl]-1H-pyrazole-3-amine, (I) (Fig. 1), which we compare briefly with methyl 4-[(5-methyl-1H-pyrazol-3-yl)amino]-3-nitrobenzoate, (II) (Portilla et al., 2007; see Scheme). Pyrazole derivatives have attracted much attention because of their potential bioactivity (Newhouse et al., 2011). In particular, aminopyrazoles containing functionalized substituents are very versatile intermediates for the synthesis of fused heterocyclic systems (Portilla et al., 2008; Quiroga et al., 2008). In addition, the introduction of a trifluoromethyl group into such compounds has often enhanced their biological activity (Jeon et al., 2007; Iaroshenko et al., 2009). As part of a synthetic study of such systems, compound (I) has been prepared in high yield by a nucleophilic aromatic substitution reaction between 5-amino-3-methyl-1H-pyrazole and 2-nitro-4-(trifluoromethyl)chlorobenzene. The reaction shows high selectivity for nucleophilic displacement by the amino group rather than by the 1H-pyrazole unit.

Perhaps the most striking feature of the molecular conformation of compound (I) is the near planarity of the molecular skeleton, as shown by the key torsion angles (Table 1). The dihedral angle between the two rings is 3.9 (2)°, while that between the aryl ring and the nitro group is only 2.1 (2)°. This near planarity may be associated with the occurrence of two short intramolecular contacts (Table 2), one each of the N—H···O and C—H···N types, forming a pair of S(6) (Bernstein et al., 1995) motifs, one to each side of the N31—C31 bond (Fig. 1). While there seems little doubt that the N—H···O contact is attractive (see below) and is thus to be regarded as a hydrogen bond, the very large value of the C3—N31—C31 angle [129.53 (14)°] suggests that the C—H···N contact may be repulsive rather than attractive. A similarly near-planar molecular skeleton was observed for compound (II) (Portilla et al., 2007). That compound also has a wide C—N—C angle at the bridging N atom [130.16 (12)°], although this was not noted in the original report. As for compound (I), this wide angle is probably associated with a repulsive intramolecular C—H···N contact.

The bond lengths associated with the aryl ring show some interesting features (Table 1). Thus, the C33—C34 and C35—C36 bond lengths, which are fairly similar to one another, are significantly shorter than the remaining C—C bond lengths within this ring. At the same time, the C32—N32 bond length is short for its type [mean value (Allen et al., 1987) = 1.468 Å, lower quartile value = 1.460 Å], while the N—O bond lengths are both long for their type (mean value = 1.217 Å). On the other hand, the C31—N31 bond length shows no shortening from the normal mean value (1.353 Å); this is certainly consistent with an intramolecular C—H···N contact which is repulsive. These observations taken together are consistent with a significant contribution to the overall electronic structure of the polarized form (Ia) (see Scheme), as well as the classical form (I). Similar patterns of bond lengths have been observed in several simple 2-nitroaniline derivatives (Cannon et al., 2001; Glidewell et al., 2001; McWilliam et al., 2001) and, indeed, in compound (II) also (Portilla et al., 2007). The charge separation in (Ia) ensures that the intramolecular N—H···O contact is attractive.

Within the pyrazole ring, the bond lengths are consistent with the location of the H atom bonded to atom N1 as deduced from a difference map. However, the C3—C4 and C4—C5 bond lengths differ by only 0.03 Å (Table 1), even though these are formally single and double bonds, respectively; similalrly, the N1—C5 and N2—C3 bond lengths differ by less than 0.02 Å, although again these are formally single and double bonds, respectively. These distances provide evidence for some aromatic-type electronic delocalization within this ring.

The molecules of (I) are linked by two hydrogen bonds, one each of the N—H···N and C—H···O types (Table 2). The molecules at (x, y, z) and (-x+2, -y, -z+1) are linked by paired N—H···N hydrogen bonds to generate a centrosymmetric R22(6) motif, while those at (x, y, z) and (-x, -y+1, -z+1) are linked by paired C—H···O hydrogen bonds forming a centrosymmetric R22(16) motif: within this ring, there is a fairly short distance, 2.706 (2) Å, between the two O1 atoms. The combination of these two cyclic motifs generates a chain running parallel to the [210] direction, in which the R22(6) rings centred at (2n+1, -n, 1/2) alternate with the R22(16) rings centred at (2n, -n+1/2, 1/2), where n represents an integer in each case (Fig. 2). There are no direction-specific attractive interactions between adjacent chains: in particular, C—H···π hydrogen bonds and aromatic ππ stacking interactions are absent from the structure of (I). The only short contacts between adjacent chains involve the nitro group O atoms of the molecule at (x, y, z) and the pyrazole and aryl rings at (-x+1, -y+1, -z+1) and (x-1, y, z), respectively, but these contacts are both probably repulsive.

It is of interest briefly to compare the supramolecular assembly of compound (I) with that of (II) (Portilla et al., 2007). The molecular constitution of these compounds differ only in the presence of a trifluoromethyl group in (I) as opposed to a methoxycabonyl group at the corresponding position in (II). Both compounds are triclinic, but their unit-cell dimensions are significantly different: in particular the cell angles in compound (I) are all greater than 90°, while those for compound (II) are all less than 90°. For neither compound is any one of the cell angles particularly close to 90°; hence there is no possibility that compounds (I) and (II) are isomorphous.

The details of the supramolecular aggregation show both similarities and differences. In compound (II), just as in compound (I), inversion-related pairs of molecules are linked by paired C—H···O hydrogen bonds to form an R22(16) motif, with a short O···O contact across the ring centre. However, by contrast with (I), there are no N—H···N hydrogen bonds in the structure of (II): instead there is an intermolecular N—H···O hydrogen bond in which the acceptor is the ketonic O atom, and a pair of such hydrogen bonds generates a centrosymmetric R22(22) motif. The combination of the two hydrogen-bonded motifs in (II) generates a chain of edge-fused rings running parallel to the [101] direction. Hence both the nature of the hydrogen bonds present, and the direction of the resulting chain differ between compounds (I) and (II), as a direct consequence of the different substituents present at position 4 of the aryl ring.

Related literature top

For related literature, see: Allen et al. (1987); Bernstein et al. (1995); Cannon et al. (2001); Glidewell et al. (2001); Iaroshenko et al. (2009); Jeon et al. (2007); McWilliam et al. (2001); Newhouse et al. (2011); Portilla et al. (2007, 2008); Quiroga et al. (2008).

Experimental top

A solution of 5-amino-3-methyl-1H-pyrazole (2 mmol) and 2-nitro-4-(trifluoromethyl)chlorobenzene (2 mmol) in a mixture of dimethyl sulfoxide and triethylamine (2:1 v/v, 3 ml) was heated at 373 K for 3 h. The mixture was permitted to cool to ambient temperature and it was then extracted with dichloromethane (4 × 25 ml). The combined organic extracts were dried over anhydrous sodium sulfate, filtered and concentrated to give (I) as an orange solid product. Orange crystals suitable for single-crystal X-ray diffraction were grown by slow evaporation, at ambient temperature and in air, of a solution in chloroform (yield 90%, m.p. 428–429 K). IR (KBr, cm-1): 1542 (NO2), 1637 (CN), 3305 (NH). MS (70 eV) m/z (%): 286 (100, M+), 240 (29), 213 (43), 199 (27), 171 (12). HRMS found m/z 286.0687, C11H9F3N4O2 requires 286.0678.

Refinement top

All H atoms were located in difference maps and subsequently treated as riding atoms in geometrically idealized positions, with C—H = 0.95 (aromatic and pyrazole) or 0.98 Å (methyl) and N—H = 0.88 Å and with Uiso(H) = kUeq(carrier), where k = 1.5 for the methyl group, which was permitted to rotate but not to tilt, and 1.2 for all other H atoms. Although the F atoms exhibit rather large anisotropic displacement parameter components, difference maps rule out any possibility these atoms might occupy more than one set of atomic sites.

Computing details top

Data collection: COLLECT (Hooft, 1999); cell refinement: DIRAX/LSQ (Duisenberg et al., 2000); data reduction: EVALCCD (Duisenberg et al., 2003); program(s) used to solve structure: SIR2004 (Burla et al., 2005); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2009); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008) and PLATON (Spek, 2009).

Figures top
[Figure 1] Fig. 1. The molecular structure of compound (I), showing the atom-labelling scheme, and the intramolecular N—H···O hydrogen bond. Displacement ellipsoids are drawn at the 30% probability level.
[Figure 2] Fig. 2. Part of the crystal structure of compound (I), showing the formation of a hydrogen-bonded chain containing R22(6) and R22(16) rings and running parallel to the [2,1,0] direction. For the sake of clarity, H atoms not involved in the motifs shown have been omitted. Atoms marked with an asterisk (*), a hash (#), a dollar sign ($) or an ampersand (&) are at the symmetry positions (-x+1, -y, -z+1), (-x, -y+1, -z+1), (x+2, y-1, z) and (x-2, y+1, z), respectively.
5-Methyl-N-[2-nitro-4-(trifluoromethyl)phenyl]-1H-pyrazole- 3-amine top
Crystal data top
C11H9F3N4O2Z = 2
Mr = 286.22F(000) = 292
Triclinic, P1Dx = 1.634 Mg m3
Hall symbol: -P 1Mo Kα radiation, λ = 0.71073 Å
a = 4.957 (2) ÅCell parameters from 2670 reflections
b = 8.737 (3) Åθ = 2.9–27.5°
c = 13.562 (5) ŵ = 0.15 mm1
α = 93.22 (3)°T = 120 K
β = 97.02 (3)°Block, orange
γ = 91.05 (3)°0.43 × 0.20 × 0.16 mm
V = 581.8 (4) Å3
Data collection top
Bruker–Nonius KappaCCD
diffractometer
2670 independent reflections
Radiation source: Bruker–Nonius FR591 rotating anode2109 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.055
Detector resolution: 9.091 pixels mm-1θmax = 27.5°, θmin = 2.9°
ϕ & ω scansh = 66
Absorption correction: multi-scan
(SADABS; Sheldrick, 2003)
k = 1111
Tmin = 0.939, Tmax = 0.977l = 1717
14609 measured reflections
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.046Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.125H-atom parameters constrained
S = 1.07 w = 1/[σ2(Fo2) + (0.0582P)2 + 0.3103P]
where P = (Fo2 + 2Fc2)/3
2670 reflections(Δ/σ)max = 0.001
182 parametersΔρmax = 0.36 e Å3
0 restraintsΔρmin = 0.30 e Å3
Crystal data top
C11H9F3N4O2γ = 91.05 (3)°
Mr = 286.22V = 581.8 (4) Å3
Triclinic, P1Z = 2
a = 4.957 (2) ÅMo Kα radiation
b = 8.737 (3) ŵ = 0.15 mm1
c = 13.562 (5) ÅT = 120 K
α = 93.22 (3)°0.43 × 0.20 × 0.16 mm
β = 97.02 (3)°
Data collection top
Bruker–Nonius KappaCCD
diffractometer
2670 independent reflections
Absorption correction: multi-scan
(SADABS; Sheldrick, 2003)
2109 reflections with I > 2σ(I)
Tmin = 0.939, Tmax = 0.977Rint = 0.055
14609 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0460 restraints
wR(F2) = 0.125H-atom parameters constrained
S = 1.07Δρmax = 0.36 e Å3
2670 reflectionsΔρmin = 0.30 e Å3
182 parameters
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
N10.8748 (3)0.09599 (17)0.58201 (10)0.0236 (3)
H11.01370.03490.59160.028*
N20.7585 (3)0.13140 (17)0.48990 (10)0.0229 (3)
C30.5602 (3)0.22565 (18)0.50934 (12)0.0189 (3)
C40.5484 (3)0.24949 (19)0.61249 (12)0.0212 (3)
H40.42470.31100.64440.025*
C50.7558 (3)0.16395 (19)0.65692 (12)0.0215 (4)
N310.3848 (3)0.29445 (16)0.43711 (10)0.0201 (3)
H310.25910.35130.46010.024*
C310.3799 (3)0.28642 (18)0.33628 (12)0.0182 (3)
C320.1950 (3)0.36955 (18)0.27219 (12)0.0187 (3)
C330.1965 (3)0.36258 (19)0.16914 (12)0.0215 (4)
H330.07200.42120.12890.026*
C340.3776 (3)0.27112 (19)0.12573 (12)0.0218 (4)
C350.5597 (3)0.18541 (19)0.18631 (13)0.0230 (4)
H350.68380.12110.15670.028*
C360.5619 (3)0.19277 (19)0.28757 (13)0.0216 (4)
H360.68860.13360.32650.026*
N320.0104 (3)0.46636 (16)0.30907 (10)0.0202 (3)
O10.0295 (2)0.47603 (14)0.39979 (9)0.0245 (3)
O20.1633 (3)0.53477 (14)0.24871 (9)0.0263 (3)
C370.3781 (4)0.2590 (2)0.01521 (14)0.0292 (4)
F10.2346 (3)0.36757 (15)0.03101 (8)0.0431 (3)
F20.2700 (3)0.12478 (15)0.02535 (9)0.0512 (4)
F30.6293 (3)0.2679 (2)0.01064 (9)0.0552 (4)
C510.8584 (4)0.1428 (2)0.76335 (13)0.0284 (4)
H51A0.84900.03370.77610.043*
H51B0.74620.20040.80640.043*
H51C1.04740.18050.77730.043*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
N10.0261 (7)0.0228 (7)0.0222 (7)0.0120 (6)0.0012 (6)0.0025 (6)
N20.0258 (7)0.0213 (7)0.0219 (7)0.0101 (6)0.0025 (6)0.0022 (6)
C30.0199 (8)0.0141 (7)0.0225 (8)0.0030 (6)0.0018 (6)0.0007 (6)
C40.0251 (8)0.0160 (8)0.0230 (8)0.0061 (6)0.0050 (6)0.0003 (6)
C50.0249 (8)0.0184 (8)0.0214 (8)0.0039 (6)0.0033 (6)0.0014 (6)
N310.0218 (7)0.0177 (7)0.0211 (7)0.0079 (5)0.0026 (5)0.0019 (5)
C310.0196 (7)0.0130 (7)0.0220 (8)0.0017 (6)0.0032 (6)0.0005 (6)
C320.0202 (8)0.0139 (7)0.0221 (8)0.0043 (6)0.0028 (6)0.0000 (6)
C330.0241 (8)0.0175 (8)0.0225 (8)0.0039 (6)0.0004 (6)0.0012 (6)
C340.0259 (8)0.0194 (8)0.0197 (8)0.0023 (6)0.0020 (6)0.0005 (6)
C350.0246 (8)0.0202 (8)0.0241 (8)0.0066 (6)0.0039 (6)0.0022 (7)
C360.0252 (8)0.0160 (8)0.0237 (8)0.0068 (6)0.0023 (6)0.0002 (6)
N320.0230 (7)0.0144 (6)0.0230 (7)0.0043 (5)0.0016 (5)0.0004 (5)
O10.0297 (6)0.0245 (6)0.0200 (6)0.0103 (5)0.0045 (5)0.0007 (5)
O20.0310 (7)0.0234 (6)0.0247 (6)0.0137 (5)0.0009 (5)0.0036 (5)
C370.0349 (10)0.0295 (10)0.0233 (9)0.0120 (8)0.0029 (7)0.0001 (7)
F10.0643 (8)0.0441 (7)0.0221 (6)0.0264 (6)0.0045 (5)0.0079 (5)
F20.0863 (10)0.0350 (7)0.0277 (6)0.0079 (7)0.0066 (6)0.0112 (5)
F30.0426 (7)0.0989 (12)0.0269 (6)0.0169 (7)0.0136 (5)0.0042 (7)
C510.0360 (10)0.0261 (9)0.0227 (9)0.0061 (8)0.0005 (7)0.0024 (7)
Geometric parameters (Å, º) top
N1—N21.365 (2)C33—H330.9500
N1—H10.8800C34—C351.401 (2)
N2—C31.335 (2)C34—C371.497 (2)
C3—N311.398 (2)C35—C361.370 (2)
C3—C41.411 (2)C35—H350.9500
C4—C51.381 (2)C36—C311.425 (2)
C4—H40.9500C36—H360.9500
C5—N11.351 (2)N31—C311.363 (2)
C5—C511.493 (2)N31—H310.8800
C32—N321.453 (2)C37—F11.335 (2)
N32—O11.2439 (18)C37—F31.336 (2)
N32—O21.2338 (18)C37—F21.341 (2)
C31—C321.422 (2)C51—H51A0.9800
C32—C331.396 (2)C51—H51B0.9800
C33—C341.376 (2)C51—H51C0.9800
C5—N1—N2113.33 (14)C33—C34—C35119.10 (15)
C5—N1—H1123.3C33—C34—C37121.13 (15)
N2—N1—H1123.3C35—C34—C37119.75 (15)
C3—N2—N1103.60 (13)C36—C35—C34121.08 (15)
N2—C3—N31124.68 (15)C36—C35—H35119.5
N2—C3—C4111.95 (14)C34—C35—H35119.5
N31—C3—C4123.36 (14)C35—C36—C31122.05 (15)
C5—C4—C3104.96 (14)C35—C36—H36119.0
C5—C4—H4127.5C31—C36—H36119.0
C3—C4—H4127.5O2—N32—O1122.11 (14)
N1—C5—C4106.16 (15)O2—N32—C32118.58 (14)
N1—C5—C51121.45 (15)O1—N32—C32119.30 (13)
C4—C5—C51132.36 (16)F1—C37—F3107.16 (16)
C31—N31—C3129.53 (14)F1—C37—F2106.00 (16)
C31—N31—H31115.2F3—C37—F2106.14 (16)
C3—N31—H31115.2F1—C37—C34113.04 (15)
N31—C31—C32123.01 (14)F3—C37—C34112.20 (15)
N31—C31—C36121.78 (15)F2—C37—C34111.82 (16)
C32—C31—C36115.21 (15)C5—C51—H51A109.5
C33—C32—C31122.29 (15)C5—C51—H51B109.5
C33—C32—N32115.25 (14)H51A—C51—H51B109.5
C31—C32—N32122.46 (15)C5—C51—H51C109.5
C34—C33—C32120.26 (15)H51A—C51—H51C109.5
C34—C33—H33119.9H51B—C51—H51C109.5
C32—C33—H33119.9
C5—N1—N2—C30.24 (19)N32—C32—C33—C34178.23 (15)
N1—N2—C3—N31179.11 (15)C32—C33—C34—C350.0 (3)
N1—N2—C3—C40.40 (18)C32—C33—C34—C37178.50 (16)
N2—C3—C4—C50.4 (2)C33—C34—C35—C360.7 (3)
N31—C3—C4—C5179.10 (15)C37—C34—C35—C36179.25 (16)
N2—N1—C5—C40.0 (2)C34—C35—C36—C310.3 (3)
N2—N1—C5—C51178.36 (15)N31—C31—C36—C35179.33 (16)
C3—C4—C5—N10.25 (19)C32—C31—C36—C350.7 (2)
C3—C4—C5—C51177.88 (18)C31—C32—N32—O11.0 (2)
N2—C3—N31—C312.2 (3)C31—C32—N32—O2179.97 (14)
C4—C3—N31—C31177.23 (16)C33—C32—N32—O1178.35 (14)
C3—N31—C31—C32176.90 (15)C33—C32—N32—O20.6 (2)
C3—N31—C31—C363.2 (3)C33—C34—C37—F113.9 (3)
N31—C31—C32—C33178.59 (15)C35—C34—C37—F1167.61 (16)
C36—C31—C32—C331.5 (2)C33—C34—C37—F3135.22 (18)
N31—C31—C32—N322.1 (2)C35—C34—C37—F346.3 (2)
C36—C31—C32—N32177.86 (14)C33—C34—C37—F2105.6 (2)
C31—C32—C33—C341.1 (3)C35—C34—C37—F272.9 (2)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1···N2i0.882.192.924 (2)141
N31—H31···O10.881.942.636 (2)135
C4—H4···O2ii0.952.433.369 (2)170
C36—H36···N20.952.202.881 (2)128
Symmetry codes: (i) x+2, y, z+1; (ii) x, y+1, z+1.

Experimental details

Crystal data
Chemical formulaC11H9F3N4O2
Mr286.22
Crystal system, space groupTriclinic, P1
Temperature (K)120
a, b, c (Å)4.957 (2), 8.737 (3), 13.562 (5)
α, β, γ (°)93.22 (3), 97.02 (3), 91.05 (3)
V3)581.8 (4)
Z2
Radiation typeMo Kα
µ (mm1)0.15
Crystal size (mm)0.43 × 0.20 × 0.16
Data collection
DiffractometerBruker–Nonius KappaCCD
diffractometer
Absorption correctionMulti-scan
(SADABS; Sheldrick, 2003)
Tmin, Tmax0.939, 0.977
No. of measured, independent and
observed [I > 2σ(I)] reflections
14609, 2670, 2109
Rint0.055
(sin θ/λ)max1)0.650
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.046, 0.125, 1.07
No. of reflections2670
No. of parameters182
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.36, 0.30

Computer programs: COLLECT (Hooft, 1999), DIRAX/LSQ (Duisenberg et al., 2000), EVALCCD (Duisenberg et al., 2003), SIR2004 (Burla et al., 2005), SHELXL97 (Sheldrick, 2008) and PLATON (Spek, 2009).

Selected geometric parameters (Å, º) top
N1—N21.365 (2)C31—C321.422 (2)
N2—C31.335 (2)C32—C331.396 (2)
C3—C41.411 (2)C33—C341.376 (2)
C4—C51.381 (2)C34—C351.401 (2)
C5—N11.351 (2)C35—C361.370 (2)
C32—N321.453 (2)C36—C311.425 (2)
N32—O11.2439 (18)N31—C311.363 (2)
N32—O21.2338 (18)
C31—N31—C3129.53 (14)
N2—C3—N31—C312.2 (3)C31—C32—N32—O11.0 (2)
C4—C3—N31—C31177.23 (16)C31—C32—N32—O2179.97 (14)
C3—N31—C31—C32176.90 (15)C33—C32—N32—O1178.35 (14)
C3—N31—C31—C363.2 (3)C33—C32—N32—O20.6 (2)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1···N2i0.882.192.924 (2)141
N31—H31···O10.881.942.636 (2)135
C4—H4···O2ii0.952.433.369 (2)170
C36—H36···N20.952.202.881 (2)128
Symmetry codes: (i) x+2, y, z+1; (ii) x, y+1, z+1.
 

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