(E)-N-[(Benzo­[b]­thio­phen-3-yl)­methyl­ene]-N'-(2,5-di­chloro­phenyl)­hydrazine

The title compound, C₁₅H₁₀Cl₂N₂S, crystallizes in the centrosymmetric space group P2₁/c with one mol­ecule in the asymmetric unit. The mol­ecule assumes an approximately planar configuration and has an E geometry about the azomethine C=N double bond. The crystal structure is stabilized by extensive hydrogen bonding.

S1. Comment

Tuberculosis is a contagious disease caused by Mycobacterium tuberculosis. After a long period in which this disease seemed to be declining, in the last two decades an unexpected return has been recorded (Raviglione et al., 1995). Isoniazid, pyraziniamide, ethambutol, rifampicin and streptomycin, generally used in combination, are still the current drugs of choice in the therapy of tuberculosis (Lounis et al., 1997). Numerous recent reports in the literature provide evidence of renewed interest, as the search for new antitubercular agents continues. A series of novel hydrazones were synthesized and screened for antitubercular activity at the Tuberculosis Antimicrobial Acquisition and Coordinating Facility (TAACF), and the title compound, (I), was found to be very active, with 96% inhibition in the preliminary screen at 6.25 µg ml⁻¹. \sch

Compound (I) was prepared by condensation of benzo[b]thiophene-3-carboxaldehyde with 2,5-dichlorophenylhydrazine to afford a single geometrical isomer. The structure of the product, (I), was initially identified by NMR spectroscopy. In order to confirm the double-bond geometry of this compound, and to obtain more detailed information on the structural conformation of the molecule which may be of value in structure-activity analysis, its X-ray structure determination has been carried out and the results are presented here.

The molecules of (I) adopt an E geometry about the azomethine C═N double bond, with atom C2 of the benzo[b]thiophene moiety and the 2,5-dichlorophenyl group on opposite sides of the C9═N10 bond. Overall, the molecule is planar, with an N11—N10—C9—C2 torsion angle of 179.3 (2)° (Fig. 1). The r.m.s. deviation of the non-H atoms from the least-squares mean plane is only 0.018 (13) Å. This configuration is in agreement with common observations in phenyl hydrazone derivatives. The N10—N11 bond distance of 1.371 (3) Å is shorter than a normal N—N single bond, as in the case of 2,4-dinitrophenylhydrazine [1.405 (6) Å; Okabe et al., 1993], which suggests delocalization of the azomethine double bond in the benzo[b]thiophene ring, and this observation is further supported by the shortened C2—C9 bond length [1.450 (4) Å] compared with the standard value for a C_ar—Csp² single bond (Wilson, 1992). Also, the N11—C12 bond distance is 1.387 (4) Å (Table 1), which indicates partial double-bond character between atom N11 and atom C12 of 2,5-dichlorophenyl ring.

Intermolecular hydrogen bonding exists between the imino H atom and the Cl atoms. The mode of packing of (I) along the a direction is illustrated in Fig. 2. van der Waal's forces contribute to the stabilization of the crystal structure.

S2. Experimental

A mixture of 2,5-dichlorophenyl hydrazine (0.531 g, 3 mmol) and benzo[b]thiophene-3-carboxaldehyde (0.487 g, 3 mmol) was dissolved in methanol (10 ml) and the solution was refluxed for 2 h. After cooling the reaction mixture, crystals of (I) formed and were collected by filtration. Recrystallization of the product from methanol afforded pale-yellow plates suitable for X-ray analysis. ¹H NMR (CDCl₃, δ, p.p.m.): 6.78 (dd, J = 7.8 and 2.4 Hz, 1H), 7.42 (d, J = 8.7 Hz, 1H), 7.44 (t, J = 7.5 Hz, 1H), 7.55 (t, J = 7.5 Hz, 1H), 7.59 (d, J = 2.4 Hz, 1H), 7.61 (s, 1H), 7.88 (d, J = 8.4 Hz, 1H), 8.00 (s, 1H), 8.69 (d, J = 7.8 Hz, 1H); ¹³C NMR (CDCl₃, δ, p.p.m.): 114.0, 115.2, 119.9, 122.8, 124.9, 125.3, 125.4, 128.8, 130.1, 131.4, 134.1, 136.0, 137.1, 140.8, 141.4.

Computing details

Data collection: COLLECT (Nonius, 1999); cell refinement: SCALEPACK (Otwinowski & Minor, 1997); data reduction: DENZO-SMN (Otwinowski & Minor, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: XP in SHELXTL/PC (Sheldrick, 1995); software used to prepare material for publication: SHELX97 and local procedures.

Figures

	Fig. 1. A view of the asymmetric unit of (I), showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii.
	Fig. 2. The crystal packing of (I), viewed along the a axis. H atoms have been omitted for clarity.

(E)—N-Benzo[b]thiophen-3-ylmethylene-N-(2,5-dichloro-phenyl)hydrazine

Crystal data

C15H10Cl2N2S	F(000) = 656
Mr = 321.21	Dx = 1.548 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 3368 reflections
a = 13.2826 (5) Å	θ = 1.0–27.5°
b = 8.7162 (3) Å	µ = 0.61 mm^−1
c = 12.7914 (4) Å	T = 90 K
β = 111.4827 (17)°	Plates, pale yellow
V = 1378.03 (8) Å^3	0.22 × 0.20 × 0.05 mm
Z = 4

Data collection

Nonius KappaCCD area-detector diffractometer	3162 independent reflections
Radiation source: fine-focus sealed tube	1987 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.058
Detector resolution: 18 pixels mm^-1	θmax = 27.5°, θmin = 1.7°
ω scans at fixed χ = 55°	h = −17→17
Absorption correction: multi-scan (SCALEPACK; Otwinowski & Minor, 1997)	k = −11→11
Tmin = 0.877, Tmax = 0.970	l = −16→16
6100 measured reflections

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.050	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.121	H-atom parameters constrained
S = 1.42	w = 1/[σ^2(Fo^2) + (0.0598P)^2] where P = (Fo^2 + 2Fc^2)/3
3162 reflections	(Δ/σ)max < 0.001
181 parameters	Δρmax = 0.45 e Å^−3
0 restraints	Δρmin = −0.30 e Å^−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. 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
Cl1	0.71660 (5)	0.27047 (9)	0.43721 (6)	0.0303 (2)
Cl2	0.56039 (6)	−0.08268 (9)	0.77189 (6)	0.0329 (2)
S1	0.03323 (6)	0.55969 (9)	0.26976 (6)	0.0298 (2)
C1	0.1657 (2)	0.5484 (3)	0.2798 (2)	0.0247 (7)
H1	0.1943	0.6098	0.2359	0.030*
C2	0.2261 (2)	0.4436 (3)	0.3563 (2)	0.0227 (7)
C3	0.1627 (2)	0.3657 (3)	0.4118 (2)	0.0219 (6)
C4	0.1925 (2)	0.2533 (3)	0.4959 (2)	0.0254 (7)
H4	0.2650	0.2170	0.5261	0.030*
C5	0.1157 (2)	0.1960 (4)	0.5344 (2)	0.0313 (7)
H5	0.1359	0.1192	0.5911	0.038*
C6	0.0101 (2)	0.2473 (3)	0.4927 (2)	0.0299 (7)
H6	−0.0411	0.2055	0.5208	0.036*
C7	−0.0218 (2)	0.3585 (3)	0.4108 (2)	0.0241 (7)
H7	−0.0945	0.3941	0.3821	0.029*
C8	0.0548 (2)	0.4175 (3)	0.3711 (2)	0.0243 (7)
C9	0.3392 (2)	0.4179 (3)	0.3752 (2)	0.0247 (7)
H9	0.3708	0.4720	0.3304	0.030*
N10	0.39821 (18)	0.3247 (3)	0.4503 (2)	0.0255 (6)
N11	0.50357 (18)	0.3101 (3)	0.4585 (2)	0.0279 (6)
H11	0.5285	0.3668	0.4164	0.033*
C12	0.5705 (2)	0.2053 (3)	0.5336 (2)	0.0224 (6)
C13	0.6750 (2)	0.1780 (3)	0.5346 (2)	0.0239 (7)
C14	0.7444 (2)	0.0769 (3)	0.6097 (2)	0.0266 (7)
H14	0.8153	0.0621	0.6100	0.032*
C15	0.7103 (2)	−0.0039 (4)	0.6854 (2)	0.0287 (7)
H15	0.7570	−0.0744	0.7375	0.034*
C16	0.6064 (2)	0.0225 (3)	0.6817 (2)	0.0264 (7)
C17	0.5361 (2)	0.1243 (3)	0.6084 (2)	0.0242 (7)
H17	0.4653	0.1391	0.6088	0.029*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cl1	0.0252 (4)	0.0358 (5)	0.0346 (4)	−0.0008 (3)	0.0166 (3)	0.0029 (4)
Cl2	0.0389 (5)	0.0331 (5)	0.0319 (4)	−0.0026 (3)	0.0192 (4)	0.0015 (3)
S1	0.0253 (4)	0.0316 (5)	0.0336 (5)	0.0030 (3)	0.0122 (3)	0.0051 (4)
C1	0.0255 (16)	0.0270 (17)	0.0248 (16)	−0.0046 (13)	0.0130 (13)	−0.0075 (13)
C2	0.0237 (15)	0.0225 (16)	0.0224 (15)	−0.0022 (13)	0.0091 (12)	−0.0025 (13)
C3	0.0224 (15)	0.0234 (16)	0.0223 (15)	−0.0039 (13)	0.0108 (12)	−0.0060 (13)
C4	0.0198 (15)	0.0259 (17)	0.0295 (16)	0.0007 (13)	0.0077 (13)	−0.0016 (14)
C5	0.0329 (18)	0.0314 (18)	0.0307 (17)	−0.0016 (14)	0.0130 (15)	0.0033 (14)
C6	0.0264 (16)	0.0341 (18)	0.0355 (17)	−0.0060 (15)	0.0188 (13)	−0.0055 (16)
C7	0.0169 (15)	0.0282 (17)	0.0289 (17)	−0.0013 (13)	0.0103 (13)	−0.0035 (14)
C8	0.0242 (16)	0.0221 (15)	0.0277 (16)	−0.0021 (13)	0.0107 (13)	−0.0054 (13)
C9	0.0246 (16)	0.0262 (16)	0.0242 (16)	−0.0035 (13)	0.0100 (13)	−0.0020 (14)
N10	0.0227 (13)	0.0272 (14)	0.0282 (14)	−0.0015 (11)	0.0114 (11)	−0.0045 (12)
N11	0.0219 (13)	0.0317 (15)	0.0334 (14)	−0.0037 (11)	0.0139 (12)	0.0014 (12)
C12	0.0247 (15)	0.0218 (16)	0.0226 (15)	−0.0022 (12)	0.0111 (13)	−0.0058 (13)
C13	0.0209 (15)	0.0262 (17)	0.0254 (16)	−0.0020 (13)	0.0093 (13)	−0.0043 (13)
C14	0.0197 (15)	0.0287 (17)	0.0327 (17)	−0.0013 (13)	0.0110 (13)	−0.0085 (14)
C15	0.0292 (17)	0.0290 (17)	0.0268 (16)	−0.0009 (14)	0.0089 (14)	−0.0024 (14)
C16	0.0323 (17)	0.0228 (16)	0.0284 (16)	−0.0082 (14)	0.0162 (14)	−0.0057 (14)
C17	0.0215 (15)	0.0273 (17)	0.0251 (16)	−0.0034 (13)	0.0102 (13)	−0.0077 (13)

Geometric parameters (Å, º)

Cl1—C13	1.735 (3)	C7—C8	1.392 (4)
Cl2—C16	1.750 (3)	C7—H7	0.9500
S1—C1	1.719 (3)	C9—N10	1.283 (3)
S1—C8	1.740 (3)	C9—H9	0.9500
C1—C2	1.363 (4)	N10—N11	1.371 (3)
C1—H1	0.9500	N11—C12	1.387 (4)
C2—C9	1.450 (4)	N11—H11	0.8800
C2—C3	1.454 (4)	C12—C17	1.394 (4)
C3—C4	1.400 (4)	C12—C13	1.403 (4)
C3—C8	1.408 (4)	C13—C14	1.379 (4)
C4—C5	1.380 (4)	C14—C15	1.400 (4)
C4—H4	0.9500	C14—H14	0.9500
C5—C6	1.380 (4)	C15—C16	1.383 (4)
C5—H5	0.9500	C15—H15	0.9500
C6—C7	1.374 (4)	C16—C17	1.378 (4)
C6—H6	0.9500	C17—H17	0.9500
C1—S1—C8	91.07 (14)	N10—C9—C2	122.3 (3)
C2—C1—S1	114.2 (2)	N10—C9—H9	118.9
C2—C1—H1	122.9	C2—C9—H9	118.9
S1—C1—H1	122.9	C9—N10—N11	116.2 (2)
C1—C2—C9	121.7 (3)	N10—N11—C12	119.4 (2)
C1—C2—C3	111.7 (2)	N10—N11—H11	120.3
C9—C2—C3	126.7 (3)	C12—N11—H11	120.3
C4—C3—C8	118.2 (2)	N11—C12—C17	121.4 (3)
C4—C3—C2	130.6 (3)	N11—C12—C13	119.9 (3)
C8—C3—C2	111.3 (2)	C17—C12—C13	118.7 (3)
C5—C4—C3	119.3 (3)	C14—C13—C12	121.4 (3)
C5—C4—H4	120.4	C14—C13—Cl1	119.3 (2)
C3—C4—H4	120.4	C12—C13—Cl1	119.3 (2)
C6—C5—C4	121.6 (3)	C13—C14—C15	120.1 (3)
C6—C5—H5	119.2	C13—C14—H14	120.0
C4—C5—H5	119.2	C15—C14—H14	120.0
C7—C6—C5	120.7 (3)	C16—C15—C14	117.6 (3)
C7—C6—H6	119.7	C16—C15—H15	121.2
C5—C6—H6	119.7	C14—C15—H15	121.2
C6—C7—C8	118.4 (3)	C17—C16—C15	123.4 (3)
C6—C7—H7	120.8	C17—C16—Cl2	118.2 (2)
C8—C7—H7	120.8	C15—C16—Cl2	118.4 (2)
C7—C8—C3	121.9 (3)	C16—C17—C12	118.8 (3)
C7—C8—S1	126.3 (2)	C16—C17—H17	120.6
C3—C8—S1	111.8 (2)	C12—C17—H17	120.6
C8—S1—C1—C2	−0.4 (2)	C1—C2—C9—N10	176.8 (3)
S1—C1—C2—C9	179.5 (2)	C3—C2—C9—N10	−3.6 (4)
S1—C1—C2—C3	−0.1 (3)	C2—C9—N10—N11	179.3 (2)
C1—C2—C3—C4	−178.9 (3)	C9—N10—N11—C12	−176.5 (2)
C9—C2—C3—C4	1.5 (5)	N10—N11—C12—C17	−5.9 (4)
C1—C2—C3—C8	0.7 (3)	N10—N11—C12—C13	173.5 (2)
C9—C2—C3—C8	−178.9 (3)	N11—C12—C13—C14	178.6 (2)
C8—C3—C4—C5	1.0 (4)	C17—C12—C13—C14	−1.9 (4)
C2—C3—C4—C5	−179.4 (3)	N11—C12—C13—Cl1	−2.7 (4)
C3—C4—C5—C6	−0.4 (4)	C17—C12—C13—Cl1	176.7 (2)
C4—C5—C6—C7	−0.1 (4)	C12—C13—C14—C15	1.5 (4)
C5—C6—C7—C8	0.1 (4)	Cl1—C13—C14—C15	−177.1 (2)
C6—C7—C8—C3	0.5 (4)	C13—C14—C15—C16	−0.3 (4)
C6—C7—C8—S1	−179.1 (2)	C14—C15—C16—C17	−0.5 (4)
C4—C3—C8—C7	−1.1 (4)	C14—C15—C16—Cl2	177.6 (2)
C2—C3—C8—C7	179.3 (2)	C15—C16—C17—C12	0.1 (4)
C4—C3—C8—S1	178.6 (2)	Cl2—C16—C17—C12	−178.0 (2)
C2—C3—C8—S1	−1.0 (3)	N11—C12—C17—C16	−179.5 (2)
C1—S1—C8—C7	−179.5 (3)	C13—C12—C17—C16	1.1 (4)
C1—S1—C8—C3	0.8 (2)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C4—H4···N10	0.95	2.49	3.059 (3)	118
C17—H17···N10	0.95	2.49	2.789 (4)	98
N11—H11···Cl1	0.88	2.56	2.960 (2)	109
N11—H11···Cl2^i	0.88	2.78	3.637 (3)	166
C17—H17···Cl2^ii	0.95	2.95	3.457 (3)	115

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