6-Iodo-1H-indole-2,3-dione

The mol­ecule of the title compound, C₈H₄INO₂, is almost planar, having an r.m.s. deviation from planarity of 0.019 Å for all non-H atoms. In the crystal, mol­ecules are linked by pairs of N—H...O hydrogen bonds, forming inversion dimers with an R₂²(8) ring motif. The dimers are further linked by I...O close contacts of 3.078 (2) Å, forming chains along [10-1]. The nine-membered fused rings of the isatin mol­ecules stack along the b axis, with parallel slipped π–π inter­actions [inter­centroid distance = 3.594 (2) Å, inter­planar distance = 3.379 (1) Å and slippage = 1.243 Å]. These inter­actions lead to the formation of a three-dimensional network.

Key indicators

• Single-crystal X-ray study
• T = 200 K
• Mean [sigma](C-C) = 0.004 Å
• R factor = 0.020
• wR factor = 0.044
• Data-to-parameter ratio = 13.7

checkCIF/PLATON results

No syntax errors found



Alert level A
PLAT073_ALERT_1_A H-atoms ref, but _hydrogen_treatment reported as     constr Check

Alert level C
PLAT369_ALERT_2_C Long    C(sp2)-C(sp2) Bond  C1     -   C2     ..       1.55 Ang.

Alert level G
PLAT002_ALERT_2_G Number of Distance or Angle Restraints on AtSite          2 Note
PLAT172_ALERT_4_G The CIF-Embedded .res File Contains DFIX Records          1 Report
PLAT431_ALERT_2_G Short Inter HL..A  Contact I1     ..  O1      ..       3.08 Ang.
PLAT860_ALERT_3_G Number of Least-Squares Restraints .............          1 Note
PLAT910_ALERT_3_G Missing # of FCF Reflection(s) Below Theta(Min)           1 Note
PLAT912_ALERT_4_G Missing # of FCF Reflections Above STh/L=  0.600          8 Note
PLAT978_ALERT_2_G Number C-C Bonds with Positive Residual Density           3 Note

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

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

---

S1. Experimental

S1.1. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 1.

S2. Results and discussion

S3. Experimental

A commercial sample (Matrix Scientific) of 6-iodo-1H-indole-2,3-dione was used for crystallization. A sample suitable for single-crystal X-ray analysis was grown from the slow evaporation of an acetone solution.

S4. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2.

Structure description

In a continuing study of the structure of halogenated isatins, we report herein on the crystal structure of 6-iodoisatin (Fig. 1). The molecule possesses bond lengths and angles similar to those observed in the parent isatin (Goldschmidt & Llewellyn, 1950). The isatins dimerize in the solid state through pairs N1—H1···O1 hydrogen bonds, forming inversion dimers with an R₂²(8) ring motif. These dimers are further linked through I1···O1 close contacts of 3.078 (2) Å that result in infinite chains along [101]; see Fig. 2 and Table 1. The nine-membered rings of the isatin stack along b with parallel slipped π–π interactions [Cg2···Cg1ⁱ = 3.594 (2) Å, inter-planar distance: 3.379 (1) Å, slippage: 1.243 Å; Cg1 and Cg2 are the centroids of rings N1/C1–C3/C8 and C3–C8, respectively; symmetry code: (i) - x + 1, - y + 1, - z + 1]. The result of these interactions is the formation of a three-dimensional structure. The I···O close contacts reported in the title compound are observed in the other three isomers of iodoisatin (Garden et al., 2006; Golen & Manke, 2016a,b). The crystal structure of 6-bromoisatin (Turbitt et al., 2016) also exhibits a similar halogen–oxygen interaction.

Computing details

Data collection: APEX2 (Bruker, 2014); cell refinement: SAINT (Bruker, 2014); data reduction: SAINT (Bruker, 2014); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: OLEX2 (Dolomanov et al., 2009); software used to prepare material for publication: OLEX2 (Dolomanov et al., 2009) and publCIF (Westrip, 2010).

Figures

	Fig. 1. Molecular structure of the title compound, showing the atom-labeling scheme. Displacement ellipsoids are drawn at the 50% probability level.
	Fig. 2. Crystal packing of the title compound viewed along the b axis, with hydrogen bonds shown as dashed lines (see Table 1), and Iodine-oxygen interactions shown as thin solid lines.

6-Iodo-1H-indole-2,3-dione

Crystal data

C8H4INO2	Z = 2
Mr = 273.02	F(000) = 256
Triclinic, P1	Dx = 2.259 Mg m^−3
a = 6.4152 (12) Å	Mo Kα radiation, λ = 0.71073 Å
b = 7.5089 (12) Å	Cell parameters from 5053 reflections
c = 8.9546 (15) Å	θ = 2.9–25.9°
α = 110.162 (7)°	µ = 3.94 mm^−1
β = 96.120 (8)°	T = 200 K
γ = 91.997 (8)°	BLOCK, yellow
V = 401.43 (12) Å^3	0.22 × 0.2 × 0.1 mm

Data collection

Bruker Venture D8 CMOS diffractometer	1428 reflections with I > 2σ(I)
Radiation source: Mo	Rint = 0.030
φ and ω scans	θmax = 25.9°, θmin = 2.9°
Absorption correction: multi-scan (SADABS; Bruker, 2014)	h = −7→7
Tmin = 0.197, Tmax = 0.259	k = −9→9
7043 measured reflections	l = −10→10
1533 independent reflections

Refinement

Refinement on F^2	1 restraint
Least-squares matrix: full	Hydrogen site location: mixed
R[F^2 > 2σ(F^2)] = 0.020	H-atom parameters constrained
wR(F^2) = 0.044	w = 1/[σ^2(Fo^2) + (0.0052P)^2 + 0.5065P] where P = (Fo^2 + 2Fc^2)/3
S = 1.13	(Δ/σ)max = 0.001
1533 reflections	Δρmax = 1.12 e Å^−3
112 parameters	Δρmin = −0.74 e Å^−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.

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

	x	y	z	Uiso*/Ueq
I1	0.88468 (3)	0.23586 (3)	0.83188 (2)	0.03175 (8)
O1	0.2881 (4)	0.1534 (3)	0.0076 (2)	0.0348 (5)
O2	0.0321 (3)	0.3232 (3)	0.2659 (3)	0.0326 (5)
N1	0.5260 (4)	0.1523 (4)	0.2204 (3)	0.0246 (5)
H1	0.621 (4)	0.087 (4)	0.168 (4)	0.030*
C1	0.3425 (5)	0.1870 (4)	0.1497 (3)	0.0244 (6)
C2	0.2080 (5)	0.2776 (4)	0.2872 (3)	0.0230 (6)
C3	0.3404 (4)	0.2856 (4)	0.4329 (3)	0.0208 (6)
C4	0.3091 (5)	0.3516 (4)	0.5932 (3)	0.0263 (6)
H4	0.1825	0.4068	0.6248	0.032*
C5	0.4653 (5)	0.3358 (4)	0.7071 (3)	0.0275 (7)
H5	0.4460	0.3788	0.8173	0.033*
C6	0.6502 (5)	0.2565 (4)	0.6580 (3)	0.0242 (6)
C7	0.6862 (5)	0.1905 (4)	0.4976 (3)	0.0229 (6)
H7	0.8137	0.1373	0.4662	0.028*
C8	0.5280 (5)	0.2063 (4)	0.3870 (3)	0.0205 (6)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
I1	0.03483 (13)	0.03183 (12)	0.02774 (12)	−0.00684 (8)	−0.01217 (8)	0.01497 (9)
O1	0.0388 (13)	0.0438 (13)	0.0224 (11)	0.0155 (11)	0.0011 (9)	0.0120 (10)
O2	0.0264 (12)	0.0370 (12)	0.0334 (12)	0.0136 (10)	0.0013 (9)	0.0106 (10)
N1	0.0219 (13)	0.0325 (13)	0.0186 (12)	0.0105 (11)	0.0028 (10)	0.0070 (10)
C1	0.0289 (16)	0.0229 (14)	0.0207 (15)	0.0066 (12)	0.0010 (12)	0.0071 (12)
C2	0.0220 (16)	0.0198 (13)	0.0264 (15)	0.0032 (12)	−0.0010 (12)	0.0079 (12)
C3	0.0214 (15)	0.0194 (13)	0.0219 (14)	0.0030 (11)	0.0008 (11)	0.0080 (11)
C4	0.0277 (17)	0.0265 (15)	0.0233 (15)	0.0036 (13)	0.0053 (12)	0.0063 (12)
C5	0.0350 (18)	0.0274 (15)	0.0189 (14)	0.0014 (13)	0.0051 (13)	0.0064 (12)
C6	0.0268 (17)	0.0222 (14)	0.0230 (14)	−0.0027 (12)	−0.0037 (12)	0.0096 (12)
C7	0.0204 (15)	0.0236 (14)	0.0242 (14)	0.0040 (11)	0.0007 (12)	0.0080 (12)
C8	0.0224 (15)	0.0196 (13)	0.0193 (14)	0.0015 (11)	0.0028 (11)	0.0066 (11)

Geometric parameters (Å, º)

I1—C6	2.096 (3)	C3—C8	1.400 (4)
O1—C1	1.217 (3)	C4—H4	0.9500
O2—C2	1.206 (3)	C4—C5	1.390 (4)
N1—H1	0.867 (10)	C5—H5	0.9500
N1—C1	1.354 (4)	C5—C6	1.392 (4)
N1—C8	1.403 (4)	C6—C7	1.396 (4)
C1—C2	1.553 (4)	C7—H7	0.9500
C2—C3	1.460 (4)	C7—C8	1.378 (4)
C3—C4	1.388 (4)
C1—N1—H1	124 (2)	C5—C4—H4	120.4
C1—N1—C8	111.5 (2)	C4—C5—H5	120.4
C8—N1—H1	124 (2)	C4—C5—C6	119.3 (3)
O1—C1—N1	128.2 (3)	C6—C5—H5	120.4
O1—C1—C2	125.7 (3)	C5—C6—I1	118.7 (2)
N1—C1—C2	106.1 (2)	C5—C6—C7	122.6 (3)
O2—C2—C1	123.7 (3)	C7—C6—I1	118.7 (2)
O2—C2—C3	131.6 (3)	C6—C7—H7	121.6
C3—C2—C1	104.7 (2)	C8—C7—C6	116.9 (3)
C4—C3—C2	132.3 (3)	C8—C7—H7	121.6
C4—C3—C8	120.3 (3)	C3—C8—N1	110.3 (2)
C8—C3—C2	107.4 (2)	C7—C8—N1	127.9 (3)
C3—C4—H4	120.4	C7—C8—C3	121.8 (3)
C3—C4—C5	119.2 (3)
I1—C6—C7—C8	179.9 (2)	C2—C3—C8—C7	−179.2 (3)
O1—C1—C2—O2	0.6 (5)	C3—C4—C5—C6	0.8 (4)
O1—C1—C2—C3	179.2 (3)	C4—C3—C8—N1	−179.1 (3)
O2—C2—C3—C4	−1.8 (6)	C4—C3—C8—C7	0.2 (4)
O2—C2—C3—C8	177.5 (3)	C4—C5—C6—I1	179.6 (2)
N1—C1—C2—O2	−178.5 (3)	C4—C5—C6—C7	−0.2 (4)
N1—C1—C2—C3	0.1 (3)	C5—C6—C7—C8	−0.3 (4)
C1—N1—C8—C3	−1.5 (3)	C6—C7—C8—N1	179.5 (3)
C1—N1—C8—C7	179.2 (3)	C6—C7—C8—C3	0.4 (4)
C1—C2—C3—C4	179.8 (3)	C8—N1—C1—O1	−178.2 (3)
C1—C2—C3—C8	−1.0 (3)	C8—N1—C1—C2	0.8 (3)
C2—C3—C4—C5	178.4 (3)	C8—C3—C4—C5	−0.7 (4)
C2—C3—C8—N1	1.5 (3)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···O1^i	0.87 (1)	2.10 (2)	2.888 (3)	152 (3)

Symmetry code: (i) −x+1, −y, −z.