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In the title compound, C7H7IN2O2, the O atoms of the nitro group are disordered over two sets of sites and there is evidence that the intramolecular I...nitro interaction is repulsive. In the crystal structure, there are neither strong hydrogen bonds, nor intermolecular I...nitro interactions, nor aromatic π–π-stacking interactions.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270101013373/gg1080sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270101013373/gg1080Isup2.hkl
Contains datablock I

CCDC reference: 174844

Comment top

In nitroanilines, the supramolecular structure is generally dominated by the effects of N—H···O hydrogen bonds (Ploug-Sørensen & Andersen, 1986; Tonogaki et al., 1993; Ellena et al., 1999; Cannon et al., 2001; Ferguson et al., 2001). When an iodo substituent is introduced, as in 2-iodo-4-nitroaniline, which crystallizes in two polymorphic forms (McWilliam et al., 2001), the supramolecular structures of both polymorphs are determined by the interplay of N—H···O hydrogen bonds, I···nitro interactions and aromatic ππ-stacking interactions. Pursuing this theme, we have now investigated the analogous compound 4-iodo-2-methyl-5-nitroaniline, (I), whose structure proves to consist of essentially isolated molecules.

In molecules of (I) (Fig. 1), the nitro group O atoms are disordered over two pairs of sites, O1A/O2A and O1B/O2B, with equal occupancies. For both orientations, the nitro group is significantly twisted out of the plane of the adjacent arene ring (Table 1), suggesting that the intramolecular I···nitro interaction may be repulsive. Consistent with this, the exocyclic bond angles at C4 and C5 (Fig. 1) differ significantly from 120°; in particular, the angles I1—C4—C3 and N2—C5—C6 are both less than 116°, consistent with I···nitro repulsion. The N2—C5—C4 angle is rather smaller than I1—C4—C5, but these values are to some extent constrained by the internal C—C—C angles, whose values, in turn, are controlled by the electronic properties of the ipso substituents (Domenicano & Murray-Rust, 1979). The C—NH2 and C—NO2 distances in (I) (Table 1) are both very much longer than the corresponding distances in 2-iodo-4-nitroaniline (McWilliam et al., 2001), but they are in fact fairly typical of those in simple 3-nitroanilines (Ploug-Sørensen & Andersen, 1986; Ellena et al., 1999; Cannon et al., 2001); the C—I distance in (I) is unexceptional, and there is no evidence from the bond distances as a whole for any electronic delocalization between substituents.

Examples of arene structures with an iodo substitutent adjacent to nitro groups are uncommon. However, in 2,4,6-trinitroiodobenzene [Cambridge Structural Database (CSD; Allen & Kennard, 1993) refcode ITNOBE01 (Weiss et al., 1999)], where the molecules lie across twofold rotation axes in space group P43212, the two exocyclic angles for the 2-nitro group, 119.8 (6)° adjacent to I and 116.6 (6)° remote from I, are consistent with I···O2N repulsion. Moreover, while the 4-nitro group is almost coplanar with the arene ring, the 2-nitro group is twisted out of the ring plane by ca 75°.

Intermolecular I···nitro interactions are generally regarded as being attractive, and indeed, they are major determinants of the supramolecular aggregation in a number of systems (Allen et al., 1994; Thalladi et al., 1996; Masciocchi et al., 1998; Ranganathan & Pedireddi, 1998; McWilliam et al., 2001). In such cases, the C—I···O angles for three-centre I···O2N interactions are typically in the range 145–165°, while in two-centre I···O(nitro) interactions the C—I···O angles often exceed 170°. By contrast, the intramolecular I···O interactions in (I) have C—I···O angles of 63.3 (2) (to O1A) and 65.1 (2)° (to O1B); likewise in ITNOBE01 (Weiss et al., 1999), where the intermolecular C—I···O angle in 161.1 (2)°, the corresponding intramolecular angle is only 61.4 (2)°. Both the I and nitro N atoms are positively polarized, while the nitro O atom is negatively polarized. In intermolecular I···nitro interactions, the difference between the I···N and I···O distances usually exceeds 1.0 Å, allowing the attractive I···O interaction to dominate, while in (I), this difference is no more than 0.5 Å even for the shortest I···O distance, with no O interposed between I and N.

The most surprising aspect of the structure of (I) is the absence of significant intermolecular interactions. The shortest intermolecular N—H···O contact has H···O and N···O distances of 2.51 and 3.325 (9) Å, respectively, both far too long for this contact to be regarded as a significant N—H···O hydrogen bond; there are no intermolecular I···O contacts less than 3.60 Å and there are no aromatic ππ-stacking interactions. The crystal structure of (I) thus differs in all respects from those of the polymorphs of 2-iodo-4-nitroaniline (McWilliam et al., 2001). Contrasts of this kind provide continuing challenges to attempts at the prediction from first principles of the crystal structures of simple molecular compounds (Lommerse et al., 2000).

Experimental top

To an aqueous solution of K[ICl2] (60 ml, 0.67 mol dm-3) (Larsen et al., 1956; Garden et al., 2001) was added rapidly a warm solution of 2-methyl-5-nitroaniline (3.00 g, 20 mmol) in methanol (40 ml). The reaction mixture was stirred at room temperature for 2 h. The solid product was collected, washed with water and air dried. Preparative thin-layer chromatography on silica using CHCl3 as eluent yielded two components, 2,4-diiodo-6-methyl-3-nitroaniline (more mobile) and 4-iodo-2-methyl-5-nitroaniline, (I) (less mobile), in a molar ratio of 1:1.2. Crystals of (I) (m.p. 377–379 K) suitable for single-crystal X-ray diffraction were grown from a solution in ethanol. NMR (p.p.m.): δH 2.12 (s, 3H, CH3), 3.88 (s, br, 2H, NH2), 7.22 (s, 1H, aromatic), 7.60 (s, 1H, aromatic); δC 16.9 (CH3), 70.7, 111.2, 129.0, 142.6, 145.4 and 150.8 (aromatic)

Refinement top

Compound (I) crystallized in the monoclinic system; space group P21/n was uniquely assigned from the systematic absences. H atoms were treated as riding atoms, with C—H distances of 0.93 Å for aromatic H atoms and 0.96 Å for methyl H atoms, and an N—H distance of 0.86 Å.

Computing details top

Data collection: KappaCCD Server Software (Nonius, 1997); cell refinement: DENZO-SMN (Otwinowski & Minor, 1997); data reduction: DENZO-SMN; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON (Spek, 2001); software used to prepare material for publication: SHELXL97 (Sheldrick, 1997) and PRPKAPPA (Ferguson, 1999).

Figures top
[Figure 1] Fig. 1. The molecule of (I) showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 30% probability level. For clarity, only one orientation of the nitro group is shown.
4-Iodo-2-methyl-5-nitroaniline top
Crystal data top
C7H7IN2O2Dx = 2.073 Mg m3
Mr = 278.05Melting point: 378 K
Monoclinic, P21/nMo Kα radiation, λ = 0.71073 Å
a = 13.5264 (7) ÅCell parameters from 2552 reflections
b = 4.2773 (2) Åθ = 1.7–30.8°
c = 16.3725 (8) ŵ = 3.56 mm1
β = 109.835 (1)°T = 150 K
V = 891.06 (8) Å3Needle, yellow
Z = 40.30 × 0.05 × 0.05 mm
F(000) = 528
Data collection top
Nonius KappaCCD
diffractometer
2552 independent reflections
Radiation source: fine-focus sealed X-ray tube2243 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.021
ϕ scans, and ω scans with κ offsetsθmax = 30.8°, θmin = 1.7°
Absorption correction: multi-scan
(DENZO-SMN; Otwinowski & Minor, 1997)
h = 1719
Tmin = 0.415, Tmax = 0.842k = 66
7521 measured reflectionsl = 2311
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)] = 0.030Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.086H-atom parameters constrained
S = 1.06 w = 1/[σ2(Fo2) + (0.0411P)2 + 1.2042P]
where P = (Fo2 + 2Fc2)/3
2552 reflections(Δ/σ)max = 0.001
129 parametersΔρmax = 1.65 e Å3
0 restraintsΔρmin = 0.88 e Å3
Crystal data top
C7H7IN2O2V = 891.06 (8) Å3
Mr = 278.05Z = 4
Monoclinic, P21/nMo Kα radiation
a = 13.5264 (7) ŵ = 3.56 mm1
b = 4.2773 (2) ÅT = 150 K
c = 16.3725 (8) Å0.30 × 0.05 × 0.05 mm
β = 109.835 (1)°
Data collection top
Nonius KappaCCD
diffractometer
2552 independent reflections
Absorption correction: multi-scan
(DENZO-SMN; Otwinowski & Minor, 1997)
2243 reflections with I > 2σ(I)
Tmin = 0.415, Tmax = 0.842Rint = 0.021
7521 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0300 restraints
wR(F2) = 0.086H-atom parameters constrained
S = 1.06Δρmax = 1.65 e Å3
2552 reflectionsΔρmin = 0.88 e Å3
129 parameters
Special details top

Experimental. The program DENZO-SMN (Otwinowski & Minor, 1997) uses a scaling algorithm [Fox, G·C. & Holmes, K·C. (1966). Acta Cryst. 20, 886–891] which effectively corrects for absorption effects. High redundancy data were used in the scaling program hence the 'multi-scan' code word was used. No transmission coefficients are available from the program (only scale factors for each frame). The scale factors in the experimental table are calculated from the 'size' command in the SHELXL97 input file.

Geometry. Mean-plane data from the final SHELXL97 refinement run:-

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/UeqOcc. (<1)
C10.2051 (2)0.3105 (8)0.13103 (19)0.0379 (6)
C20.1255 (2)0.4752 (8)0.1124 (2)0.0409 (6)
C30.1456 (2)0.5994 (8)0.0304 (2)0.0414 (6)
C40.2426 (2)0.5756 (7)0.03505 (19)0.0377 (6)
C50.3211 (2)0.4137 (8)0.01510 (18)0.0371 (6)
C60.3035 (3)0.2823 (8)0.0657 (2)0.0405 (7)
N10.1888 (3)0.1926 (8)0.2136 (2)0.0528 (8)
C70.0187 (3)0.5155 (12)0.1811 (3)0.0615 (10)
I10.253476 (19)0.78094 (6)0.153999 (14)0.04779 (10)
N20.4275 (2)0.3717 (9)0.07844 (18)0.0486 (7)
O1A0.4656 (6)0.570 (3)0.1318 (5)0.072 (2)0.50
O2A0.4692 (5)0.1125 (19)0.0764 (4)0.0672 (17)0.50
O1B0.4447 (6)0.437 (3)0.1538 (5)0.071 (2)0.50
O2B0.4984 (5)0.299 (2)0.0523 (6)0.079 (2)0.50
H30.09170.70380.01860.050*
H60.35720.17430.07680.049*
H110.23930.10130.22490.063*
H120.12820.21090.25340.063*
H710.01550.31600.19450.092*
H720.02670.60240.23260.092*
H730.02310.65390.16000.092*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
C10.0405 (14)0.0444 (16)0.0263 (13)0.0061 (12)0.0079 (11)0.0018 (11)
C20.0342 (13)0.0506 (17)0.0324 (14)0.0021 (12)0.0039 (11)0.0055 (12)
C30.0368 (14)0.0484 (17)0.0377 (15)0.0030 (13)0.0111 (12)0.0041 (13)
C40.0420 (14)0.0405 (15)0.0301 (13)0.0026 (12)0.0116 (11)0.0032 (11)
C50.0326 (13)0.0453 (16)0.0291 (12)0.0029 (11)0.0047 (10)0.0057 (12)
C60.0360 (14)0.0494 (17)0.0341 (15)0.0016 (12)0.0094 (12)0.0021 (12)
N10.0499 (16)0.073 (2)0.0305 (14)0.0046 (14)0.0066 (12)0.0095 (13)
C70.0405 (17)0.082 (3)0.049 (2)0.0037 (18)0.0017 (14)0.002 (2)
I10.05915 (16)0.05196 (15)0.03392 (13)0.00600 (9)0.01796 (10)0.00378 (8)
N20.0399 (14)0.0678 (19)0.0320 (13)0.0011 (14)0.0043 (11)0.0027 (13)
O1A0.040 (3)0.116 (8)0.050 (5)0.012 (4)0.003 (3)0.026 (5)
O2A0.050 (3)0.086 (5)0.056 (3)0.024 (3)0.006 (3)0.009 (3)
O1B0.050 (4)0.108 (8)0.040 (4)0.012 (4)0.003 (3)0.003 (4)
O2B0.037 (3)0.126 (7)0.068 (5)0.007 (3)0.010 (3)0.012 (4)
Geometric parameters (Å, º) top
C1—C21.405 (5)N2—O1B1.208 (8)
C2—C31.382 (5)N2—O2A1.250 (8)
C3—C41.387 (4)N2—O2B1.217 (8)
C4—C51.396 (4)C3—H30.9300
C5—C61.382 (5)C6—H60.9300
C6—C11.401 (4)N1—H110.8600
C2—C71.510 (4)N1—H120.8600
C4—I12.095 (3)C7—H710.9600
C1—N11.388 (4)C7—H720.9600
C5—N21.472 (4)C7—H730.9600
N2—O1A1.202 (9)
N1—C1—C6120.5 (3)C1—C6—H6119.8
N1—C1—C2120.9 (3)C1—N1—H11120.0
C6—C1—C2118.5 (3)C1—N1—H12120.0
C3—C2—C1119.4 (3)H11—N1—H12120.0
C3—C2—C7120.3 (3)C2—C7—H71109.5
C1—C2—C7120.4 (3)C2—C7—H72109.5
C2—C3—C4123.1 (3)H71—C7—H72109.5
C2—C3—H3118.5C2—C7—H73109.5
C4—C3—H3118.5H71—C7—H73109.5
C3—C4—C5116.7 (3)H72—C7—H73109.5
I1—C4—C3115.9 (2)O1B—N2—O2B121.1 (6)
I1—C4—C5127.3 (2)O1A—N2—O2A124.1 (6)
C6—C5—C4121.9 (3)O1A—N2—C5120.1 (5)
N2—C5—C6115.8 (3)O1B—N2—C5119.7 (5)
N2—C5—C4122.4 (3)O2B—N2—C5118.8 (4)
C5—C6—C1120.4 (3)O2A—N2—C5115.6 (4)
C5—C6—H6119.8
N1—C1—C2—C3177.6 (3)C4—C5—C6—C10.5 (5)
C6—C1—C2—C31.0 (5)N2—C5—C6—C1179.5 (3)
N1—C1—C2—C72.6 (5)N1—C1—C6—C5176.7 (3)
C6—C1—C2—C7179.2 (3)C2—C1—C6—C50.1 (5)
C1—C2—C3—C41.4 (5)C6—C5—N2—O1A147.6 (6)
C7—C2—C3—C4178.8 (3)C4—C5—N2—O1A32.5 (7)
C2—C3—C4—C50.8 (5)C4—C5—N2—O2A142.2 (5)
C2—C3—C4—I1179.7 (3)C6—C5—N2—O1B168.7 (6)
C3—C4—C5—C60.2 (5)C4—C5—N2—O1B11.2 (8)
I1—C4—C5—C6178.5 (2)C4—C5—N2—O2B162.1 (6)
C3—C4—C5—N2179.9 (3)C6—C5—N2—O2B17.9 (7)
I1—C4—C5—N21.4 (4)C6—C5—N2—O2A37.8 (6)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H12···O1Bi0.862.513.325 (9)158
N1—H12···O1Ai0.862.653.406 (9)148
N1—H11···N1ii0.862.383.174 (5)153
Symmetry codes: (i) x1/2, y+1/2, z1/2; (ii) x+1/2, y1/2, z1/2.

Experimental details

Crystal data
Chemical formulaC7H7IN2O2
Mr278.05
Crystal system, space groupMonoclinic, P21/n
Temperature (K)150
a, b, c (Å)13.5264 (7), 4.2773 (2), 16.3725 (8)
β (°) 109.835 (1)
V3)891.06 (8)
Z4
Radiation typeMo Kα
µ (mm1)3.56
Crystal size (mm)0.30 × 0.05 × 0.05
Data collection
DiffractometerNonius KappaCCD
diffractometer
Absorption correctionMulti-scan
(DENZO-SMN; Otwinowski & Minor, 1997)
Tmin, Tmax0.415, 0.842
No. of measured, independent and
observed [I > 2σ(I)] reflections
7521, 2552, 2243
Rint0.021
(sin θ/λ)max1)0.720
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.030, 0.086, 1.06
No. of reflections2552
No. of parameters129
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)1.65, 0.88

Computer programs: KappaCCD Server Software (Nonius, 1997), DENZO-SMN (Otwinowski & Minor, 1997), DENZO-SMN, SHELXS97 (Sheldrick, 1997), PLATON (Spek, 2001), SHELXL97 (Sheldrick, 1997) and PRPKAPPA (Ferguson, 1999).

Selected geometric parameters (Å, º) top
C1—C21.405 (5)C4—I12.095 (3)
C2—C31.382 (5)C1—N11.388 (4)
C3—C41.387 (4)C5—N21.472 (4)
C4—C51.396 (4)N2—O1A1.202 (9)
C5—C61.382 (5)N2—O1B1.208 (8)
C6—C11.401 (4)N2—O2A1.250 (8)
C2—C71.510 (4)N2—O2B1.217 (8)
I1—C4—C3115.9 (2)N2—C5—C6115.8 (3)
I1—C4—C5127.3 (2)N2—C5—C4122.4 (3)
C4—C5—N2—O1A32.5 (7)C4—C5—N2—O1B11.2 (8)
C4—C5—N2—O2A142.2 (5)C4—C5—N2—O2B162.1 (6)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H12···O1Bi0.862.513.325 (9)158
N1—H12···O1Ai0.862.653.406 (9)148
N1—H11···N1ii0.862.383.174 (5)153
Symmetry codes: (i) x1/2, y+1/2, z1/2; (ii) x+1/2, y1/2, z1/2.
 

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