2,4-Diiodo­aniline

Abstract

The structure of the title compound, C₆H₅I₂N, shows a weak inter­molecular amine–amine N—H⋯N hydrogen-bonding inter­action, giving a helical chain which extends along the a axis. An intra­molecular N—H⋯I hydrogen bond is also observed.

Related literature

For related structures, see: Garden et al. (2002 ▶). For the synthesis, see: Dains et al. (1935 ▶); Hodgson & Marsden (1937 ▶); O’Neil (2001 ▶). For graph-set analysis of hydrogen bonding, see: Etter et al. (1990 ▶).

Experimental

Crystal data

• C₆H₅I₂N

• M _r = 344.91

• Orthorhombic,

• a = 4.3870 (1) Å

• b = 10.9626 (3) Å

• c = 16.9778 (4) Å

• V = 816.51 (3) ų

• Z = 4

• Mo Kα radiation

• μ = 7.62 mm⁻¹

• T = 200 K

• 0.30 × 0.18 × 0.18 mm

Data collection

• Oxford Diffraction Gemini-S Ultra CCD-detector diffractometer

• Absorption correction: multi-scan (SADABS; Sheldrick, 1996 ▶) T _min = 0.146, T _max = 0.250

• 6739 measured reflections

• 1873 independent reflections

• 1790 reflections with I > 2σ(I)

• R _int = 0.024

Refinement

• R[F ² > 2σ(F ²)] = 0.018

• wR(F ²) = 0.038

• S = 1.05

• 1873 reflections

• 90 parameters

• H atoms treated by a mixture of independent and constrained refinement

• Δρ_max = 0.38 e Å⁻³

• Δρ_min = −0.47 e Å⁻³

• Absolute structure: Flack (1983 ▶), 737 Friedel pairs

• Flack parameter: −0.03 (4)

Data collection: CrysAlis CCD (Oxford Diffraction, 2008 ▶); cell refinement: CrysAlis RED (Oxford Diffraction, 2008 ▶); data reduction: CrysAlis RED; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶) within WinGX (Farrugia, 1999 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶) within WinGX (Farrugia, 1999 ▶); molecular graphics: PLATON (Spek, 2009 ▶); software used to prepare material for publication: PLATON.

Supplementary Material

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H11⋯I2	0.77 (3)	2.81 (3)	3.283 (4)	122 (3)
N1—H12⋯N1i	0.80 (4)	2.30 (4)	3.106 (5)	180 (5)

Symmetry code: (i) .

supplementary crystallographic information

Comment

Although the crystal structures of a number of nitro-substituted iodoanilines including 3-nitro-2,4-diodoaniline have been reported (Garden et al., 2002), that of the title compound 2,4-diiodoaniline C₆H₆I₂N (I) has not been determined and the structure is reported here. The compound was isolated as the major crystalline product in the attempted synthesis of an adduct of 4,5-dichlorophthalic acid with 4-iodoaniline in aqueous ethanol. This conversion of 4-iodoaniline to 2,4-diiodoaniline has been reported previously (Dains et al., 1935), where solid 4-iodoaniline was observed to undergo a ca 25% conversion to the diiodo analogue in a sealed container over a period of three years. Hodgson & Marsden (1937) also reported the ready formation of the diiodo derivative along with 4-iodoaniline from the reaction of aniline with iodine.

In the structure of (I) (Fig. 1), single weak intermolecular hydrogen bonds are found [N1—H1···N1ⁱ, 3.106 (5) Å; symmetry code: (i) x - 1/2, -y + 3/2, -z + 2] [graph set S(4) (Etter et al., 1990)], linking the amine groups of 2₁ screw-related molecules. These form one-dimensional chains which extend down the a cell direction in the unit cell (Fig. 2).

In this structure there are, not unexpectedly, short intramoleculer N—H···I interactions [N1···I2, 3.283 (4) Å], which are also present in the structure of 2,4-diiodo-3-nitroaniline [3.254 (7) Å (Garden et al., 2002)]. However, unlike the nitro-derivative, no π–π stacking interactions are present in the structure of (I).

Experimental

The title compound was formed in the attempted synthesis of a proton-transfer salt of 4,5-dichlorophthalic acid with 4-iodoaniline by heating together under reflux for 10 minutes 1 mmol quantities of the two reagents in 50 ml of 50% ethanol-water. After concentration to ca 30 ml, partial room temperature evaporation of the hot-filtered solution gave colourless needle prisms of 2,4-diiodoaniline [m.p. 368–389 K (O'Neil, 2001)] as the major product. This conversion of 4-iodoaniline to 2,4-diiodoaniline in the solid state has been reported previously (Dains et al., 1935).

Refinement

The hydrogen atoms of the amino group were located in a difference Fourier map and their positional and isotropic displacement parameters were refined freely. Other H-atoms were included in the refinement in calculated positions [C—H = 0.93 Å) and treated using a riding model approximation, with U_iso(H) = 1.2U_eq(C).

Figures

Fig. 1.

Molecular configuration and atom naming scheme for (I). Displacement ellipsoids are drawn at the 50% probability level.

Fig. 2.

The one-dimensional hydrogen-bonded chain structure of (I) extending down the a axial direction of the unit cell, showing hydrogen-bonding associations as dashed lines. Non-interactive H atoms are omitted. [Symmetry code (i): x - 1/2, -y + 3/2, -z + 2].

Crystal data

C6H5I2N	Dx = 2.806 Mg m−3
Mr = 344.91	Melting point = 368–369 K
Orthorhombic, P212121	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2ac 2ab	Cell parameters from 5620 reflections
a = 4.3870 (1) Å	θ = 3.0–32.2°
b = 10.9626 (3) Å	µ = 7.62 mm−1
c = 16.9778 (4) Å	T = 200 K
V = 816.51 (3) Å3	Needle, colourless
Z = 4	0.30 × 0.18 × 0.18 mm
F(000) = 616

Data collection

Oxford Diffraction Gemini-S Ultra CCD-detector diffractometer	1873 independent reflections
Radiation source: Enhance (Mo) X-ray tube	1790 reflections with I > 2σ(I)
graphite	Rint = 0.024
ω scans	θmax = 27.5°, θmin = 3.0°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −5→5
Tmin = 0.146, Tmax = 0.250	k = −13→14
6739 measured reflections	l = −22→18

Refinement

Refinement on F2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.018	H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.038	w = 1/[σ2(Fo2) + (0.0207P)2] where P = (Fo2 + 2Fc2)/3
S = 1.05	(Δ/σ)max = 0.003
1873 reflections	Δρmax = 0.38 e Å−3
90 parameters	Δρmin = −0.47 e Å−3
0 restraints	Absolute structure: Flack (1983), 737 Friedel pairs
Primary atom site location: structure-invariant direct methods	Flack parameter: −0.03 (4)

Special details

Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
I2	0.57888 (5)	0.42657 (2)	1.08868 (1)	0.0293 (1)
I4	0.48489 (5)	0.28546 (2)	0.75021 (1)	0.0330 (1)
N1	0.1721 (9)	0.6552 (3)	1.0212 (2)	0.0291 (11)
C1	0.2299 (7)	0.5690 (3)	0.9630 (2)	0.0218 (9)
C2	0.4096 (8)	0.4658 (3)	0.97570 (19)	0.0221 (9)
C3	0.4807 (8)	0.3859 (3)	0.9156 (2)	0.0247 (9)
C4	0.3689 (8)	0.4074 (3)	0.8407 (2)	0.0235 (10)
C5	0.1876 (8)	0.5075 (3)	0.8256 (2)	0.0260 (11)
C6	0.1216 (9)	0.5877 (3)	0.8865 (2)	0.0278 (11)
H3	0.60280	0.31820	0.92530	0.0300*
H5	0.11070	0.52100	0.77530	0.0310*
H6	0.00190	0.65580	0.87610	0.0330*
H11	0.190 (8)	0.626 (3)	1.062 (2)	0.038 (9)*
H12	0.043 (8)	0.704 (4)	1.010 (2)	0.040 (9)*

Atomic displacement parameters (Ų)

	U11	U22	U33	U12	U13	U23
I2	0.0335 (1)	0.0341 (1)	0.0202 (1)	0.0009 (1)	−0.0038 (1)	0.0021 (1)
I4	0.0383 (1)	0.0389 (1)	0.0219 (1)	0.0022 (1)	0.0017 (1)	−0.0069 (1)
N1	0.037 (2)	0.0222 (16)	0.028 (2)	0.0055 (15)	−0.0021 (16)	0.0013 (15)
C1	0.0214 (15)	0.0191 (16)	0.0248 (18)	−0.0039 (15)	0.0014 (14)	0.0021 (14)
C2	0.0251 (16)	0.0226 (16)	0.0186 (17)	−0.0034 (15)	−0.0009 (14)	0.0032 (11)
C3	0.0289 (18)	0.0218 (14)	0.0234 (17)	−0.0007 (11)	−0.0010 (16)	0.0015 (12)
C4	0.0252 (17)	0.0226 (18)	0.0228 (18)	−0.0031 (13)	0.0028 (14)	−0.0029 (13)
C5	0.027 (2)	0.0313 (19)	0.0197 (19)	−0.0028 (14)	−0.0018 (15)	0.0044 (14)
C6	0.0323 (19)	0.0236 (18)	0.0276 (19)	0.0028 (15)	0.0007 (15)	0.0051 (13)

Geometric parameters (Å, °)

I2—C2	2.101 (3)	C2—C3	1.381 (5)
I4—C4	2.099 (3)	C3—C4	1.383 (5)
N1—C1	1.391 (5)	C4—C5	1.379 (5)
N1—H12	0.80 (4)	C5—C6	1.388 (5)
N1—H11	0.77 (3)	C3—H3	0.9300
C1—C6	1.398 (5)	C5—H5	0.9300
C1—C2	1.396 (5)	C6—H6	0.9300
H11—N1—H12	124 (4)	I4—C4—C3	118.6 (2)
C1—N1—H11	110 (3)	C3—C4—C5	120.7 (3)
C1—N1—H12	114 (3)	C4—C5—C6	119.1 (3)
N1—C1—C6	119.9 (3)	C1—C6—C5	121.9 (3)
N1—C1—C2	123.0 (3)	C2—C3—H3	120.00
C2—C1—C6	117.0 (3)	C4—C3—H3	120.00
I2—C2—C1	120.4 (2)	C4—C5—H5	120.00
I2—C2—C3	117.7 (2)	C6—C5—H5	121.00
C1—C2—C3	121.9 (3)	C1—C6—H6	119.00
C2—C3—C4	119.4 (3)	C5—C6—H6	119.00
I4—C4—C5	120.7 (2)
N1—C1—C2—I2	5.0 (5)	C1—C2—C3—C4	−0.7 (5)
N1—C1—C2—C3	−175.5 (3)	C2—C3—C4—I4	179.3 (3)
C6—C1—C2—I2	−178.9 (2)	C2—C3—C4—C5	0.0 (5)
C6—C1—C2—C3	0.6 (5)	I4—C4—C5—C6	−178.5 (3)
N1—C1—C6—C5	176.5 (3)	C3—C4—C5—C6	0.9 (5)
C2—C1—C6—C5	0.3 (5)	C4—C5—C6—C1	−1.0 (5)
I2—C2—C3—C4	178.8 (3)

Hydrogen-bond geometry (Å, °)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H11···I2	0.77 (3)	2.81 (3)	3.283 (4)	122 (3)
N1—H12···N1i	0.80 (4)	2.30 (4)	3.106 (5)	180 (5)

Symmetry codes: (i) x−1/2, −y+3/2, −z+2.