Crystal structure of 4-chloro-2-iodo­aniline

In the crystal structure of the title compound, C₆H₅ClIN, the amino group engages in N—H⋯N hydrogen bonding, creating [100] chains. A Cl⋯I contact is observed [3.7850 (16) Å]. The parallel planes of neigbouring mol­ecules reveal highly offset π-stacking characterized by a centroid–centroid distance of 4.154 (1), a centroid-to-plane distance of 3.553 (3) and ring-offset slippage of 2.151 (6) Å.

1. Related literature

For the synthesis and vibrational spectroscopic analysis of 4-chloro-2-iodo­aniline, see: Hoque et al. (2013). For the dehalo­genation of dihalogenated anilines in human liver microsomes, see: Zhang et al. (2011). For the crystal structures of related monohalogenated anilines, see: Trotter et al. (1966); Parkin et al. (2005) and of dihalogenated anilines, see: Xu et al. (2008). For halogen–halogen inter­actions, see: Pedireddi et al. (1994) and for π-stacking, see: Lueckheide et al. (2013). For van der Waals radii, see: Bondi (1964).

2. Experimental

2.1. Crystal data

• C₆H₅ClIN

• M_r = 253.46

• Orthorhombic, P 2₁ 2₁ 2₁

• a = 4.1538 (4) Å

• b = 11.3685 (11) Å

• c = 15.8550 (16) Å

• V = 748.71 (13) ų

• Z = 4

• Mo Kα radiation

• μ = 4.54 mm⁻¹

• T = 125 K

• 0.20 × 0.10 × 0.05 mm

2.2. Data collection

• Bruker APEXII CCD diffractometer

• Absorption correction: multi-scan (SADABS; Bruker, 2007) T_min = 0.56, T_max = 0.81

• 11850 measured reflections

• 2281 independent reflections

• 2007 reflections with I > 2σ(I)

• R_int = 0.066

2.3. Refinement

• R[F² > 2σ(F²)] = 0.029

• wR(F²) = 0.053

• S = 1.02

• 2281 reflections

• 88 parameters

• 2 restraints

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

• Δρ_max = 0.96 e Å⁻³

• Δρ_min = −1.03 e Å⁻³

• Absolute structure: Flack x determined using 742 quotients [(I⁺)−(I⁻)]/[(I⁺)+(I⁻)] (Parsons et al., 2013)

• Absolute structure parameter: −0.03 (3)

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H2⋯N1^ii	0.90 (2)	2.28 (3)	3.142 (6)	161 (5)
Symmetry code: (ii) .

Data collection: APEX2 (Bruker, 2007); cell refinement: SAINT (Bruker, 2007); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2008); molecular graphics: SHELXTL2014 (Sheldrick, 2008); software used to prepare material for publication: SHELXTL2014, OLEX2 (Dolomanov et al., 2009) and Mercury (Macrae et al., 2006).

Supporting information

S1. Structural commentary

Dihalogenated anilines such as the title compound exhibit different toxicities depending on the identity, number and substitution pattern of the halogens on the aniline ring, and the mechanism of halogen activiation in differently substituted dihalogenated anilines by gluta­thione has been studied using human liver microsomes (Zhang et al., 2011). The title compound may be synthesized using selective ortho-iodination of 4-chloro­aniline (Hoque et al., 2013). The C—Cl and C—I bond lengths of 1.755 (6) Å and 2.101 (5) Å in the title compound (Fig. 1) are similar to those found in the corresponding mono-substituted anilines, 4-chloro­aniline with C—Cl bond length 1.75 Å (Trotter et al., 1966) and 2-iodo­aniline with C—I bond length 2.103 (7) Å (Parkin et al., 2005). Further, the C—Cl and C—I bond lengths are similar to those found in the isomer where the positions of the halides are reversed, 2-chloro-4-iodo­aniline, with C—Cl bond length 1.742 (4) Å and C—I bond length 2.103 (4) Å (Xu et al., 2008).

In the structure of the titular compound, cooperative inter­molecular hydrogen bonding with one of the two amine protons, H2, links the molecules into a one-dimensional chain running down the crystallographic a-axis (Fig. 2, Table 1). The other amine proton, H1, does not engage in any significant hydrogen bonding inter­action. There is also an inter­molecular halogen-halogen inter­action between chlorine and iodine, with a Cl···Iⁱ distance of 3.7850 (16) Å (Fig. 3) which is slightly longer than the sum of the van der Waals radii of chlorine and iodine, 3.73 Å (Bondi, 1964) [symmetry code (i): x - 1/2, -y + 3/2, -z]. For a discussion of halogen···halogen inter­actions, see Pedireddi et al., 1994. The parallel planes of neigboring aromatic molecules reveal a highly offset face-to-face π-stacking (Fig. 3) characterized by a ring centroid-to-centroid distance of 4.154 (1) Å, centroid-to-plane distance of 3.553 (3) Å, and ring-offset slippage parameter of 2.151 (6) Å (Lueckheide et al., 2013).

S2. Synthesis and crystallization

Crystalline 4-Chloro-2-iodo­aniline (I) was purchased from Aldrich Chemical Company, USA.

S3. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 1. All non-hydrogen atoms were refined anisotropically. Hydrogen atoms on carbon were included in calculated positions and refined using a riding model at C–H = 0.95 Å and U_iso(H) = 1.2 × U_eq(C) of the aryl C-atoms. The hydrogen atoms on nitro­gen were located in the difference map and refined semifreely with the help of a distance restraint, d(N—H) 0.90 (2) Å and U_iso(H) = 1.2 × U_eq(N). The extinction parameter (EXTI) refined to zero and was removed from the refinement.

Related literature

For the synthesis and vibrational spectroscopic analysis of 4-chloro-2-iodoaniline, see: Hoque et al. (2013). For the dehalogenation of dihalogenated anilines in human liver microsomes, see: Zhang et al. (2011). For the crystal structures of related monohalogenated anilines, see: Trotter et al. (1966); Parkin et al. (2005) and of dihalogenated anilines, see: Xu et al. (2008). For halogen–halogen interactions, see: Pedireddi et al. (1994) and for π-stacking, see: Lueckheide et al. (2013). For van der Waals radii, see: Bondi (1964).

Computing details

Data collection: APEX2 (Bruker, 2007); cell refinement: SAINT (Bruker, 2007); data reduction: SAINT (Bruker, 2007); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2008); molecular graphics: SHELXTL2014 (Sheldrick, 2008); software used to prepare material for publication: SHELXTL2014 (Sheldrick, 2008), OLEX2 (Dolomanov et al., 2009) and Mercury (Macrae et al., 2006).

Figures

	Fig. 1. A view of title compound, with atom numbering scheme. Displacement ellipsoids are shown at the 50% probability level.
	Fig. 2. A view of the hydrogen bonding in 4-Chloro-2-iodoaniline forming a chain parallel to the crystallographic a-axis. Displacement ellipsoids are shown at the 50% probability level; hydrogen atoms on carbon removed for clarity. For symmetry code (ii), see Table 1.
	Fig. 3. A view of the offset face-to-face π-stacking and Cl···I^i contact (thick solid line) in the packing of 4-Chloro-2-iodoaniline. Displacement ellipsoids are shown at the 50% probability level. Symmetry code (i): x - 1/2, -y + 3/2, -z.

4-Chloro-2-iodoaniline

Crystal data

C6H5ClIN	F(000) = 472
Mr = 253.46	Dx = 2.249 Mg m^−3
Orthorhombic, P212121	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2ac 2ab	Cell parameters from 5580 reflections
a = 4.1538 (4) Å	θ = 2.2–30.3°
b = 11.3685 (11) Å	µ = 4.54 mm^−1
c = 15.8550 (16) Å	T = 125 K
V = 748.71 (13) Å^3	Plate, colourless
Z = 4	0.20 × 0.10 × 0.05 mm

Data collection

Bruker APEXII CCD diffractometer	2281 independent reflections
Radiation source: fine-focus sealed tube	2007 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.066
Detector resolution: 8.3333 pixels mm^-1	θmax = 30.5°, θmin = 2.2°
ϕ and ω scans	h = −5→5
Absorption correction: multi-scan (SADABS; Bruker, 2007)	k = −16→16
Tmin = 0.56, Tmax = 0.81	l = −22→22
11850 measured reflections

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: mixed
R[F^2 > 2σ(F^2)] = 0.029	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.053	w = 1/[σ^2(Fo^2) + (0.0156P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 1.02	(Δ/σ)max = 0.001
2281 reflections	Δρmax = 0.96 e Å^−3
88 parameters	Δρmin = −1.03 e Å^−3
2 restraints	Absolute structure: Flack x determined using 742 quotients [(I^+)-(I^-)]/[(I^+)+(I^-)] (Parsons et al., 2013)
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: −0.03 (3)

Special details

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refined as a 2-component inversion twin.

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

	x	y	z	Uiso*/Ueq
I1	1.19309 (8)	0.92075 (3)	−0.09588 (2)	0.02161 (9)
Cl1	1.0100 (4)	0.80636 (12)	0.24943 (10)	0.0322 (3)
N1	0.8012 (13)	1.1528 (4)	−0.0258 (3)	0.0236 (9)
H1	0.795 (14)	1.124 (5)	−0.0783 (19)	0.028*
H2	0.625 (10)	1.196 (4)	−0.017 (4)	0.028*
C1	0.8463 (11)	1.0685 (4)	0.0375 (3)	0.0187 (10)
C2	1.0139 (12)	0.9638 (4)	0.0242 (3)	0.0167 (10)
C3	1.0695 (12)	0.8840 (4)	0.0886 (3)	0.0190 (10)
H3	1.1867	0.8136	0.0784	0.023*
C4	0.9513 (13)	0.9087 (5)	0.1680 (3)	0.0233 (11)
C5	0.7803 (14)	1.0111 (5)	0.1839 (4)	0.0255 (12)
H5	0.6977	1.0266	0.2387	0.031*
C6	0.7316 (12)	1.0906 (4)	0.1191 (3)	0.0228 (11)
H6	0.6182	1.1615	0.1301	0.027*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
I1	0.01729 (14)	0.02359 (15)	0.02395 (16)	0.00030 (14)	0.00153 (14)	−0.00153 (15)
Cl1	0.0468 (9)	0.0259 (7)	0.0238 (7)	0.0013 (7)	−0.0056 (6)	0.0049 (6)
N1	0.027 (2)	0.0132 (19)	0.031 (3)	0.003 (2)	−0.001 (3)	0.0002 (18)
C1	0.014 (2)	0.013 (2)	0.029 (3)	−0.002 (2)	−0.003 (2)	−0.001 (2)
C2	0.015 (3)	0.016 (2)	0.019 (3)	−0.0008 (19)	−0.001 (2)	−0.002 (2)
C3	0.018 (2)	0.014 (2)	0.024 (3)	0.0009 (18)	−0.003 (2)	−0.003 (2)
C4	0.025 (3)	0.021 (3)	0.024 (3)	−0.003 (3)	−0.004 (2)	0.002 (2)
C5	0.026 (3)	0.026 (3)	0.025 (3)	−0.003 (2)	0.001 (2)	−0.004 (2)
C6	0.023 (3)	0.015 (2)	0.030 (3)	0.002 (2)	−0.001 (2)	−0.007 (2)

Geometric parameters (Å, º)

I1—C2	2.101 (5)	C2—C3	1.386 (7)
Cl1—C4	1.755 (6)	C3—C4	1.380 (7)
Cl1—I1^i	3.7850 (16)	C3—H3	0.95
N1—C1	1.400 (7)	C4—C5	1.387 (8)
N1—H1	0.90 (2)	C5—C6	1.383 (7)
N1—H2	0.90 (2)	C5—H5	0.95
C1—C2	1.395 (7)	C6—H6	0.95
C1—C6	1.402 (7)
Cl1···I1^i	3.7850 (16)
C4—Cl1—I1^i	86.03 (18)	C4—C3—H3	120.7
C1—N1—H1	115 (4)	C2—C3—H3	120.7
C1—N1—H2	112 (4)	C3—C4—C5	121.3 (5)
H1—N1—H2	109 (5)	C3—C4—Cl1	119.1 (4)
C2—C1—N1	122.9 (5)	C5—C4—Cl1	119.6 (4)
C2—C1—C6	117.5 (5)	C6—C5—C4	119.2 (5)
N1—C1—C6	119.5 (5)	C6—C5—H5	120.4
C3—C2—C1	122.0 (5)	C4—C5—H5	120.4
C3—C2—I1	117.2 (4)	C5—C6—C1	121.3 (5)
C1—C2—I1	120.8 (4)	C5—C6—H6	119.4
C4—C3—C2	118.7 (5)	C1—C6—H6	119.4
N1—C1—C2—C3	176.8 (5)	I1^i—Cl1—C4—C3	−49.3 (4)
C6—C1—C2—C3	−0.5 (7)	I1^i—Cl1—C4—C5	129.0 (4)
N1—C1—C2—I1	−3.3 (7)	C3—C4—C5—C6	−0.9 (8)
C6—C1—C2—I1	179.4 (4)	Cl1—C4—C5—C6	−179.2 (4)
C1—C2—C3—C4	0.8 (8)	C4—C5—C6—C1	1.2 (8)
I1—C2—C3—C4	−179.1 (4)	C2—C1—C6—C5	−0.5 (7)
C2—C3—C4—C5	−0.1 (8)	N1—C1—C6—C5	−177.9 (5)
C2—C3—C4—Cl1	178.2 (4)

Symmetry code: (i) x−1/2, −y+3/2, −z.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H2···N1^ii	0.90 (2)	2.28 (3)	3.142 (6)	161 (5)

Symmetry code: (ii) x−1/2, −y+5/2, −z.