4,5-Diiodo-2-phenyl-1H-imidazole

The structure of the title compound, C₉H₆I₂N₂, contains two symmetry-independent mol­ecules. The inter­planar angles between the imidazole and phenyl ring planes are 16.35 (3) and 17.48 (6)°. Mol­ecules are connected via N—H...N hydrogen bonds to form zigzag chains along the b axis. The title compound is the first example of a structurally characterized 4,5-diiodo­imidazole with an organic substituent in the 2-position and without protection on the N—H group of imidazole.

Key indicators

• Single-crystal X-ray study
• T = 150 K
• Mean [sigma](C-C) = 0.007 Å
• R factor = 0.029
• wR factor = 0.051
• Data-to-parameter ratio = 20.9

checkCIF/PLATON results

No syntax errors found



Alert level C
PLAT910_ALERT_3_C Missing # of FCF Reflections Below Th(Min) .....          1
PLAT911_ALERT_3_C Missing # FCF Refl Between THmin & STh/L=  0.600         11
PLAT913_ALERT_3_C Missing # of Very Strong Reflections in FCF ....          3

Alert level G
ABSTY01_ALERT_1_G  Extra text has been found in the _exptl_absorpt_correction_type
            field, which should be only a single keyword. A literature
            citation should be included in the _exptl_absorpt_process_details
            field.
REFLT03_ALERT_4_G Please check that the estimate of the number of Friedel pairs is
            correct. If it is not, please give the correct count in the
            _publ_section_exptl_refinement section of the submitted CIF.
           From the CIF: _diffrn_reflns_theta_max           27.50
           From the CIF: _reflns_number_total               4914
           Count of symmetry unique reflns         2699
           Completeness (_total/calc)            182.07%
           TEST3: Check Friedels for noncentro structure
           Estimate of Friedel pairs measured      2215
           Fraction of Friedel pairs measured     0.821
           Are heavy atom types Z>Si present        yes
PLAT005_ALERT_5_G No _iucr_refine_instructions_details in CIF ....          ?
PLAT007_ALERT_5_G Note: Number of Unrefined D-H Atoms ............          2
PLAT083_ALERT_2_G SHELXL Second Parameter in WGHT Unusually Large.       8.58

   0 ALERT level A = Most likely a serious problem - resolve or explain
   0 ALERT level B = A potentially serious problem, consider carefully
   3 ALERT level C = Check. Ensure it is not caused by an omission or oversight
   5 ALERT level G = General information/check it is not something unexpected

   1 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   1 ALERT type 2 Indicator that the structure model may be wrong or deficient
   3 ALERT type 3 Indicator that the structure quality may be low
   1 ALERT type 4 Improvement, methodology, query or suggestion
   2 ALERT type 5 Informative message, check

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S1. Comment

Halogenated derivatives of heterocycles are important starting compounds for building new heterocyclic chiral ligands via cross-coupling reactions. In recent times 4,5-diiodoimidazole and its derivatives were used for the preparation of various disubstituted 4,5-dicarbaimidazoles (Zhang et al., 2006; Ito & Uedaira, 2004; Kim et al., 1999; Haruki et al., 1965). To the best of our knowledge, there are a couple of structures of dihalogenated imidazoles determined by X-ray diffraction methods, but the 4,5-diido-1H-imidazole structure as the most versatile and simpliest member of the series is missing. Compound I (Scheme 1) was separated as a byproduct from a reaction described by Ishihara (Ishihara & Togo, 2006) but is usually prepared by the method of Garden (Garden et al., 2001). The title compound crystallizes (Fig. 1) in an orthorhombic space group with two independent molecules in the unit cell (Fig. 2). Both molecules reveal similar structural behavior showing two planar conjugated rings – phenyl and imidazolyl. The interplanar angles between imidazolyl and phenyl planes are 16.35 (3)° and 17.48 (6)°, respectively. The formation of infinite chains is provided by the connection of both types of molecules via N–H···N hydrogen bridges. The linear chains interact via the iodine atoms at neighbouring imidazole moieties. In contrast to typical C–I bond lenghts of ca. 2.095 Å (Allen et al., 1987) which is the same for monoiodoimidazoles, the C–I separations in diiodoimidazoles significantly differ between ca. 2.05 and 2.09 Å (Panday et al., 2000; Terinek & Vasella, 2003). This phenomenon is also seen in one of the molecules of I, where the C11–I3 bond length is 2.075 (5) Å and the C12–I4 bond located next to the N–H function is shortened to 2.058 (5) Å. On the other hand, in the first molecule both C–I bond lenghts (2.051 (5) and 2.058 (5) Å) are almost identical and thus comparable to the same parameters found in compounds containing the 4,5-diidoimidazolium ion (Mukai & Nishikawa, 2010a,b). Only one iodine atom I1 is located in the same plane defined by the imidazole ring, while the others show deviations of 0.07-0.148 Å. Bond lenghts between the atoms forming the imidazole rings are comparable to literature values (Allen et al., 1987) except of C1–N2 which is elongated by 0.02 Å and C10–N3 which is slightly shortened.

Related literature

For the structures of various related compounds, see: Delest et al. (2008); Poverlein et al. (2007); Panday et al. (2000); Phillips et al. (1997); Terinek & Vasella (2003); Mukai & Nishikawa (2010a,b); Noland et al. (2003); Dou & Weiss (1992); Nagatomo et al. (1995). For the use of diiodoimidazoles as starting compounds for ligand synthesis, see: Haruki et al. (1965); Ito & Uedaira (2004); Kim et al. (1999); Zhang et al. (2006). For the synthetic procedure, see: Garden et al. (2001); Ishihara & Togo (2006). For typical bond lengths, see: Allen et al. (1987).

S2. Experimental

The title compound I was isolated in 30% yield as a byproduct from the reaction mixture of 2-phenyl-1H-imidazole-4-carbaldehyde with ethan-1,2-diamine, iodine and potassium carbonate in tert-butylalcohol, according to Ishihara (Ishihara & Togo, 2006) in order to prepare 2'-phenyl-4,5-dihydro-1H,1'H-2,4'-biimidazole. The reaction mixture was separated by the help of column chromatography on silicagel (ethyl acetate, hexane and dichloromethane – 1:3:10). Further crystallization from dichloromethane gave pure I. The identity and purity of I was confirmed by the same melting point, ¹H NMR and mass spectra patterns as published elsewhere (Garden et al., 2001). Single crystals of I were obtained by slow vapour diffussion of hexane into a solution of I in dichloromethane.

S3. Refinement

All hydrogen atoms were discernible in the difference electron density map. However, all hydrogen atoms were placed into idealized positions and refined riding on their parent C or N atoms, with N–H = 0.86 Å, C–H = 0.93 Å for aromatic H atoms, with U(H) = 1.2U_eq(C/N) for the NH group and U(H) = 1.5U_eq(C/N) for other H atoms, respectively.

Computing details

Data collection: COLLECT (Hooft, 1998) and DENZO (Otwinowski & Minor, 1997); cell refinement: COLLECT (Hooft, 1998) and DENZO (Otwinowski & Minor, 1997); data reduction: COLLECT (Hooft, 1998) and DENZO (Otwinowski & Minor, 1997); program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2009); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures

	Fig. 1. View of one of the independent molecules of the title compound with the displacement ellipsoids shown at the 50% probability level. H atoms are shown with arbitrary radii.
	Fig. 2. View of the crystal structure down the c axis showing the hydrogen bond interactions.

4,5-Diiodo-2-phenyl-1H-imidazole

Crystal data

C9H6I2N2	Dx = 2.409 Mg m^−3
Mr = 395.96	Melting point: 472 K
Orthorhombic, Aba2	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: A 2 -2ac	Cell parameters from 20579 reflections
a = 31.0150 (6) Å	θ = 1–27.5°
b = 17.5010 (5) Å	µ = 5.72 mm^−1
c = 8.0461 (9) Å	T = 150 K
V = 4367.4 (5) Å^3	Needle, colourless
Z = 16	0.45 × 0.16 × 0.07 mm
F(000) = 2880

Data collection

Bruker–Nonius KappaCCD area-detector diffractometer	4914 independent reflections
Radiation source: fine-focus sealed tube	4499 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.058
Detector resolution: 9.091 pixels mm^-1	θmax = 27.5°, θmin = 2.3°
ϕ and ω scans to fill the Ewald sphere	h = −39→40
Absorption correction: gaussian (Coppens, 1970)	k = −22→19
Tmin = 0.256, Tmax = 0.675	l = −9→10
20468 measured reflections

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.029	H-atom parameters constrained
wR(F^2) = 0.051	w = 1/[σ^2(Fo^2) + (0.0196P)^2 + 8.5806P] where P = (Fo^2 + 2Fc^2)/3
S = 1.04	(Δ/σ)max = 0.001
4914 reflections	Δρmax = 0.63 e Å^−3
235 parameters	Δρmin = −0.63 e Å^−3
1 restraint	Absolute structure: Flack (1983), 2233 Friedel pairs
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.01 (3)

Special details

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

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 > 2sigma(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
I3	0.239603 (10)	0.127609 (18)	0.00147 (5)	0.02406 (8)
I2	0.185474 (11)	0.465127 (18)	0.86344 (5)	0.02557 (9)
I1	0.142369 (12)	0.262855 (18)	0.73764 (5)	0.02639 (9)
I4	0.225974 (10)	0.324363 (17)	0.26443 (4)	0.02035 (8)
N1	0.11736 (13)	0.3687 (2)	0.4558 (5)	0.0172 (9)
N3	0.14573 (13)	0.1439 (2)	0.0814 (5)	0.0160 (8)
C14	0.05141 (17)	0.1305 (3)	0.0519 (7)	0.0210 (12)
H14	0.0683	0.1040	−0.0242	0.025*
C9	0.11213 (17)	0.5450 (3)	0.2022 (6)	0.0217 (12)
H9	0.1321	0.5741	0.2610	0.026*
C3	0.15163 (16)	0.4339 (3)	0.6553 (6)	0.0166 (10)
C1	0.11925 (16)	0.4415 (3)	0.4126 (6)	0.0153 (10)
C4	0.10087 (15)	0.4731 (2)	0.2585 (7)	0.0178 (10)
C13	0.07108 (16)	0.1796 (3)	0.1643 (6)	0.0151 (10)
C11	0.18543 (15)	0.1775 (3)	0.1070 (6)	0.0163 (10)
C2	0.13758 (15)	0.3637 (3)	0.6074 (6)	0.0146 (10)
C12	0.18168 (16)	0.2429 (3)	0.1949 (6)	0.0170 (10)
C10	0.11796 (16)	0.1907 (3)	0.1591 (6)	0.0150 (10)
N2	0.13961 (13)	0.4833 (2)	0.5321 (5)	0.0184 (9)
H2	0.1441	0.5318	0.5297	0.022*
C18	0.04545 (16)	0.2180 (3)	0.2794 (7)	0.0219 (11)
H18	0.0582	0.2511	0.3556	0.026*
C5	0.07161 (18)	0.4297 (3)	0.1697 (7)	0.0269 (13)
H5	0.0637	0.3815	0.2079	0.032*
C16	−0.01789 (19)	0.1579 (3)	0.1692 (8)	0.0301 (14)
H16	−0.0476	0.1507	0.1714	0.036*
N4	0.13889 (12)	0.2501 (2)	0.2280 (6)	0.0147 (8)
H4	0.1273	0.2867	0.2834	0.018*
C17	0.00127 (17)	0.2077 (3)	0.2786 (8)	0.0296 (13)
H17	−0.0156	0.2343	0.3548	0.035*
C15	0.00750 (18)	0.1195 (3)	0.0545 (8)	0.0284 (13)
H15	−0.0053	0.0865	−0.0215	0.034*
C8	0.0937 (2)	0.5739 (3)	0.0577 (7)	0.0313 (14)
H8	0.1005	0.6230	0.0224	0.038*
C7	0.0656 (2)	0.5299 (3)	−0.0314 (8)	0.0343 (15)
H7	0.0542	0.5487	−0.1302	0.041*
C6	0.0541 (2)	0.4581 (3)	0.0261 (8)	0.0347 (15)
H6	0.0350	0.4285	−0.0352	0.042*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
I3	0.02447 (18)	0.02458 (16)	0.02313 (18)	0.00572 (12)	0.00691 (17)	−0.00173 (16)
I2	0.03117 (19)	0.02441 (17)	0.02114 (18)	0.00247 (14)	−0.01031 (16)	−0.00504 (16)
I1	0.0322 (2)	0.01704 (15)	0.0299 (2)	−0.00235 (14)	−0.00951 (16)	0.00849 (16)
I4	0.01828 (16)	0.01997 (15)	0.02279 (17)	−0.00410 (12)	−0.00100 (14)	−0.00314 (15)
N1	0.019 (2)	0.012 (2)	0.020 (2)	0.0002 (16)	−0.0024 (17)	−0.0020 (17)
N3	0.022 (2)	0.0113 (19)	0.014 (2)	0.0012 (16)	−0.0021 (17)	−0.0004 (17)
C14	0.023 (3)	0.019 (3)	0.021 (3)	0.003 (2)	−0.003 (2)	−0.002 (2)
C9	0.030 (3)	0.018 (3)	0.017 (3)	−0.003 (2)	−0.001 (2)	0.000 (2)
C3	0.016 (2)	0.017 (2)	0.017 (3)	−0.0009 (19)	−0.002 (2)	0.001 (2)
C1	0.019 (3)	0.013 (2)	0.014 (3)	−0.0019 (19)	−0.0007 (19)	0.0012 (19)
C4	0.020 (2)	0.019 (2)	0.014 (3)	0.0032 (19)	0.002 (2)	0.000 (2)
C13	0.021 (3)	0.011 (2)	0.014 (3)	0.0038 (18)	−0.006 (2)	0.0051 (19)
C11	0.019 (2)	0.013 (2)	0.017 (3)	0.0060 (18)	0.004 (2)	−0.001 (2)
C2	0.015 (2)	0.015 (2)	0.014 (3)	0.0024 (18)	0.003 (2)	0.0008 (19)
C12	0.018 (3)	0.014 (2)	0.019 (3)	−0.0025 (19)	0.001 (2)	0.001 (2)
C10	0.024 (3)	0.010 (2)	0.012 (2)	−0.0031 (18)	−0.001 (2)	−0.0004 (18)
N2	0.024 (2)	0.0103 (19)	0.021 (3)	0.0011 (16)	−0.0028 (18)	−0.0033 (17)
C18	0.022 (3)	0.018 (2)	0.027 (3)	0.0016 (19)	−0.001 (2)	−0.001 (2)
C5	0.028 (3)	0.019 (3)	0.034 (3)	−0.003 (2)	−0.008 (2)	0.005 (2)
C16	0.020 (3)	0.037 (3)	0.033 (4)	−0.008 (2)	−0.002 (3)	0.001 (3)
N4	0.017 (2)	0.0127 (18)	0.014 (2)	0.0015 (15)	−0.0053 (17)	−0.0043 (17)
C17	0.017 (3)	0.034 (3)	0.038 (4)	−0.001 (2)	0.002 (3)	0.002 (3)
C15	0.023 (3)	0.031 (3)	0.031 (3)	−0.006 (2)	−0.010 (2)	0.000 (2)
C8	0.045 (4)	0.024 (3)	0.026 (3)	−0.006 (2)	−0.009 (3)	0.007 (2)
C7	0.047 (4)	0.030 (3)	0.026 (4)	0.003 (3)	−0.015 (3)	0.009 (3)
C6	0.044 (4)	0.030 (3)	0.030 (4)	−0.013 (2)	−0.020 (3)	0.004 (3)

Geometric parameters (Å, º)

I3—C11	2.075 (5)	C13—C10	1.467 (7)
I2—C3	2.051 (5)	C11—C12	1.350 (7)
I1—C2	2.058 (5)	C12—N4	1.360 (6)
I4—C12	2.058 (5)	C10—N4	1.345 (6)
N1—C1	1.323 (6)	N2—H2	0.8600
N1—C2	1.374 (6)	C18—C17	1.382 (7)
N3—C10	1.343 (6)	C18—H18	0.9300
N3—C11	1.379 (6)	C5—C6	1.370 (8)
C14—C15	1.376 (8)	C5—H5	0.9302
C14—C13	1.388 (7)	C16—C17	1.374 (8)
C14—H14	0.9301	C16—C15	1.388 (9)
C9—C4	1.381 (7)	C16—H16	0.9299
C9—C8	1.391 (8)	N4—H4	0.8600
C9—H9	0.9301	C17—H17	0.9300
C3—C2	1.360 (7)	C15—H15	0.9299
C3—N2	1.366 (6)	C8—C7	1.367 (8)
C1—N2	1.363 (6)	C8—H8	0.9301
C1—C4	1.472 (7)	C7—C6	1.385 (8)
C4—C5	1.383 (7)	C7—H7	0.9299
C13—C18	1.393 (7)	C6—H6	0.9299
C1—N1—C2	105.9 (4)	N4—C10—C13	124.7 (4)
C10—N3—C11	104.1 (4)	C1—N2—C3	107.4 (4)
C15—C14—C13	120.8 (5)	C1—N2—H2	126.0
C15—C14—H14	119.8	C3—N2—H2	126.6
C13—C14—H14	119.3	C17—C18—C13	120.0 (5)
C4—C9—C8	120.1 (5)	C17—C18—H18	120.3
C4—C9—H9	119.9	C13—C18—H18	119.8
C8—C9—H9	120.0	C6—C5—C4	119.8 (5)
C2—C3—N2	106.2 (4)	C6—C5—H5	120.3
C2—C3—I2	129.5 (4)	C4—C5—H5	120.0
N2—C3—I2	124.3 (3)	C17—C16—C15	119.2 (5)
N1—C1—N2	110.6 (4)	C17—C16—H16	120.2
N1—C1—C4	124.5 (4)	C15—C16—H16	120.6
N2—C1—C4	124.9 (4)	C10—N4—C12	108.6 (4)
C9—C4—C5	119.8 (5)	C10—N4—H4	126.0
C9—C4—C1	121.4 (4)	C12—N4—H4	125.4
C5—C4—C1	118.9 (4)	C16—C17—C18	121.0 (5)
C14—C13—C18	118.7 (5)	C16—C17—H17	119.8
C14—C13—C10	119.9 (4)	C18—C17—H17	119.2
C18—C13—C10	121.4 (4)	C14—C15—C16	120.2 (5)
C12—C11—N3	111.2 (4)	C14—C15—H15	120.0
C12—C11—I3	129.8 (4)	C16—C15—H15	119.7
N3—C11—I3	118.9 (3)	C7—C8—C9	119.8 (5)
C3—C2—N1	109.9 (4)	C7—C8—H8	120.4
C3—C2—I1	127.4 (4)	C9—C8—H8	119.9
N1—C2—I1	122.6 (3)	C8—C7—C6	119.9 (5)
C11—C12—N4	105.4 (4)	C8—C7—H7	119.4
C11—C12—I4	132.2 (4)	C6—C7—H7	120.6
N4—C12—I4	122.3 (3)	C5—C6—C7	120.6 (5)
N3—C10—N4	110.7 (4)	C5—C6—H6	119.9
N3—C10—C13	124.6 (4)	C7—C6—H6	119.4

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N2—H2···N3^i	0.86	2.01	2.845 (5)	165
N4—H4···N1	0.86	2.02	2.848 (6)	162

Symmetry code: (i) x, y+1/2, z+1/2.