organic compounds
2,2′-Dithiodianiline: a redetermination at 100 K
aX-ray Crystallography Unit, School of Physics, Universiti Sains Malaysia, 11800 USM, Penang, Malaysia, and bDepartment of Studies in Chemistry, Mangalore University, Mangalagangotri, Mangalore 574 199, India
*Correspondence e-mail: hkfun@usm.my
Structural studies of the title compound [systematic name: 2,2′-(disulfanediyl)dianiline], C12H12N2S2, were previously performed at room temperature [Gomes de Mesquita (1967). Acta Cryst. 23, 671; Lee & Bryant (1970). Acta Cryst. B26, 1729; Ribar et al. (1975). Bull. Yugoslav. Crystallogr. Centre, A10, 68]. The results of the current redetermination allow a clarification of the nature of the intra- and intermolecular N—H⋯S hydrogen bonding described in the literature for this compound. On cooling to 100 K, the contracts most in the c axis, and it changes rather less in the directions involving the strongly hydrogen-bonded chains, which are the a and b axes. In the N—H⋯N hydrogen bonds link neighbouring molecules into two-dimensional frameworks parallel to the ab plane. An additional intermolecular N—H⋯S hydrogen bond has also been established, based on freely refined H-atom positions. Intermolecular C—H⋯π interactions further stabilize the crystal structure.
Related literature
For previously reported structure determinations of the title compound, see: Gomes de Mesquita (1967); Lee & Bryant (1970); Ribar et al. (1975). For general background to and applications of the title compound, see: Garbarczyk et al. (1999); Kalluraya et al. (2000); Kalluraya & Chimbalkar (2001). For a description of the Cambridge Structural Database, see: Allen (2002). For the stability of the temperature controller used for the data collection, see: Cosier & Glazer (1986).
Experimental
Crystal data
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Refinement
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Data collection: APEX2 (Bruker, 2009); cell SAINT (Bruker, 2009); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009).
Supporting information
https://doi.org/10.1107/S1600536810000024/tk2598sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536810000024/tk2598Isup2.hkl
The title compound is obtained by exposing 2-aminobenzenethiol to sunlight in an open beaker for two days. The reagent 2-aminobenzenethiol undergoes self aerial oxidation to furnish the crystals. The crude product obtained through the photochemical condition was washed with ethanol and dried. Single crystals suitable for X-ray analysis were obtained from ethanol by slow evaporation.
All the H atoms were located from difference Fourier map [range of C—H = 0.93 (3) - 1.00 (3) Å, and see Table 1 for N–H distances] and allowed to refine freely.
Nitrogen- and sulphur- containing compounds are important intermediates in the synthesis of various
Ortho amino thiophenols are important precursors in the preparation of a variety of heterocycles such as benzothiadiazepines, thiadiazoles, thiadiazines etc. (Kalluraya et al., 2000; Kalluraya & Chimbalkar, 2001). The title compound was obtained during an attempt to study the aerial oxidation of aminothiophenols. Molecular and crystal structures of thioamide derivatives have been analyzed (Garbarczyk et al., 1999).A search of the November 2008 release of the Cambridge Structural Database (Allen, 2002) reveals that the room temperature crystal structures of the title compound (Fig. 1) were first reported with R = 0.057 for 369 reflections (Gomes de Mesquita, 1967), then followed with R = 0.086 for 1313 reflections (Lee & Bryant, 1970) and R = 0.042 (Ribar et al., 1975). The current redetermination at 100 K increases significantly the precision of the structural and geometrical parameters and provides a lower R value (R = 0.048 based on 2750 independent observed reflections).
Comparison with the previously reported π interactions only whereas along the a and b axes, the molecules are interconnected by the stronger hydrogen bonds (Figs 2 & 3, Table 1). The previously reported structure (Lee & Bryant, 1970) suggests two intramolecular N—H···S hydrogen bonds, but the current work observes no such intramolecular hydrogen bonds with bond angle larger than 120°. The bond lengths are comparable to but more precise than the previously reported structures (Lee & Bryant, 1970; Ribar et al., 1975).
parameters (Ribar et al., 1975) reveals that on cooling to 100 K, a expands by 0.41 %, whereas b and c contract by 1.15 and 1.74 %, respectively. This can be explained by the fact that along the c axis, the molecules are interconnected by weak C—H···In the
molecules are linked into two-dimensional frameworks parallel to the ab plane (Fig. 3) rather than one-dimensional infinite chains as reported previously (Lee & Bryant, 1970). Based on freely refined hydrogen atom positions, an additional intermolecular N2—H2N2···S1 hydrogen bond (Table 1) has also been established. Intermolecular C4—H4A···Cg1 and C9—H9A···Cg2 interactions (Table 1) further stabilize the crystal structure.For previously reported structure determinations of the title compound, see: Gomes de Mesquita (1967); Lee & Bryant (1970); Ribar et al. (1975). For general background to and applications of the title compound, see: Garbarczyk et al. (1999); Kalluraya et al. (2000); Kalluraya & Chimbalkar (2001). For a description of the Cambridge Structural Database, see: Allen (2002). For the stability of the temperature controller used for the data collection, see: Cosier & Glazer (1986).
Data collection: APEX2 (Bruker, 2009); cell
SAINT (Bruker, 2009); data reduction: SAINT (Bruker, 2009); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).Fig. 1. The molecular structure of the title compound, showing 50% probability displacement ellipsoids for non-H atoms and the atom-numbering scheme. | |
Fig. 2. Part of the crystal structure, viewed along the a axis, showing two interlayers being joined along the c axis by weak intermolecular C—H···π interactions. Hydrogen atoms not involved in intermolecular interactions (dashed lines) have been omitted for clarity. | |
Fig. 3. The crystal structure of the title compound, viewed along the c axis, showing a two-dimensional framework parallel to the ab plane. Intermolecular hydrogen bonds are shown as dashed lines. |
C12H12N2S2 | F(000) = 1040 |
Mr = 248.36 | Dx = 1.372 Mg m−3 |
Orthorhombic, Pbca | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2ac 2ab | Cell parameters from 9179 reflections |
a = 8.2531 (1) Å | θ = 3.1–29.9° |
b = 13.0278 (2) Å | µ = 0.42 mm−1 |
c = 22.3655 (4) Å | T = 100 K |
V = 2404.73 (6) Å3 | Block, yellow |
Z = 8 | 0.23 × 0.18 × 0.17 mm |
Bruker SMART APEXII CCD area-detector diffractometer | 2750 independent reflections |
Radiation source: fine-focus sealed tube | 2417 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.040 |
φ and ω scans | θmax = 27.5°, θmin = 3.1° |
Absorption correction: multi-scan (SADABS; Bruker, 2009) | h = −10→10 |
Tmin = 0.912, Tmax = 0.934 | k = −16→16 |
47724 measured reflections | l = −29→29 |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.048 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.124 | All H-atom parameters refined |
S = 1.19 | w = 1/[σ2(Fo2) + (0.0383P)2 + 5.2113P] where P = (Fo2 + 2Fc2)/3 |
2750 reflections | (Δ/σ)max < 0.001 |
193 parameters | Δρmax = 0.50 e Å−3 |
0 restraints | Δρmin = −0.43 e Å−3 |
C12H12N2S2 | V = 2404.73 (6) Å3 |
Mr = 248.36 | Z = 8 |
Orthorhombic, Pbca | Mo Kα radiation |
a = 8.2531 (1) Å | µ = 0.42 mm−1 |
b = 13.0278 (2) Å | T = 100 K |
c = 22.3655 (4) Å | 0.23 × 0.18 × 0.17 mm |
Bruker SMART APEXII CCD area-detector diffractometer | 2750 independent reflections |
Absorption correction: multi-scan (SADABS; Bruker, 2009) | 2417 reflections with I > 2σ(I) |
Tmin = 0.912, Tmax = 0.934 | Rint = 0.040 |
47724 measured reflections |
R[F2 > 2σ(F2)] = 0.048 | 0 restraints |
wR(F2) = 0.124 | All H-atom parameters refined |
S = 1.19 | Δρmax = 0.50 e Å−3 |
2750 reflections | Δρmin = −0.43 e Å−3 |
193 parameters |
Experimental. The crystal was placed in the cold stream of an Oxford Cyrosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1)K. |
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. |
x | y | z | Uiso*/Ueq | ||
S1 | 0.02244 (8) | 0.44246 (5) | 0.29158 (3) | 0.02175 (17) | |
S2 | −0.18075 (7) | 0.49532 (5) | 0.33614 (3) | 0.01897 (17) | |
N1 | 0.1434 (3) | 0.65943 (19) | 0.27327 (11) | 0.0261 (5) | |
N2 | −0.3466 (3) | 0.28926 (19) | 0.32376 (10) | 0.0226 (5) | |
C1 | 0.2321 (3) | 0.6022 (2) | 0.31445 (12) | 0.0208 (5) | |
C2 | 0.3664 (3) | 0.6450 (2) | 0.34391 (13) | 0.0267 (6) | |
C3 | 0.4491 (3) | 0.5893 (2) | 0.38682 (14) | 0.0308 (7) | |
C4 | 0.4032 (3) | 0.4902 (2) | 0.40210 (13) | 0.0287 (6) | |
C5 | 0.2712 (3) | 0.4467 (2) | 0.37320 (12) | 0.0233 (5) | |
C6 | 0.1857 (3) | 0.5017 (2) | 0.32969 (11) | 0.0193 (5) | |
C7 | −0.2077 (3) | 0.40351 (19) | 0.39331 (11) | 0.0171 (5) | |
C8 | −0.1543 (3) | 0.4247 (2) | 0.45123 (12) | 0.0220 (5) | |
C9 | −0.1837 (3) | 0.3567 (2) | 0.49755 (12) | 0.0275 (6) | |
C10 | −0.2661 (4) | 0.2664 (2) | 0.48554 (13) | 0.0295 (6) | |
C11 | −0.3206 (3) | 0.2437 (2) | 0.42842 (13) | 0.0251 (6) | |
C12 | −0.2934 (3) | 0.31171 (19) | 0.38114 (11) | 0.0190 (5) | |
H2A | 0.402 (4) | 0.715 (3) | 0.3335 (14) | 0.034 (9)* | |
H3A | 0.536 (4) | 0.621 (3) | 0.4078 (15) | 0.038 (9)* | |
H4A | 0.457 (4) | 0.451 (3) | 0.4337 (15) | 0.033 (9)* | |
H5A | 0.240 (4) | 0.379 (2) | 0.3819 (13) | 0.025 (8)* | |
H8A | −0.100 (4) | 0.492 (2) | 0.4590 (14) | 0.027 (8)* | |
H9A | −0.153 (4) | 0.373 (2) | 0.5377 (14) | 0.022 (8)* | |
H10A | −0.285 (4) | 0.219 (3) | 0.5158 (14) | 0.030 (9)* | |
H11A | −0.374 (4) | 0.179 (3) | 0.4193 (14) | 0.029 (8)* | |
H1N1 | 0.199 (5) | 0.706 (3) | 0.2542 (18) | 0.048 (11)* | |
H2N1 | 0.083 (5) | 0.620 (3) | 0.2483 (16) | 0.040 (10)* | |
H1N2 | −0.422 (5) | 0.244 (3) | 0.3209 (15) | 0.037 (9)* | |
H2N2 | −0.362 (4) | 0.343 (3) | 0.3004 (14) | 0.025 (8)* |
U11 | U22 | U33 | U12 | U13 | U23 | |
S1 | 0.0167 (3) | 0.0245 (3) | 0.0240 (3) | −0.0045 (2) | 0.0039 (2) | −0.0044 (3) |
S2 | 0.0123 (3) | 0.0188 (3) | 0.0258 (3) | −0.0004 (2) | 0.0000 (2) | 0.0029 (2) |
N1 | 0.0241 (12) | 0.0220 (12) | 0.0321 (13) | 0.0011 (10) | 0.0068 (10) | 0.0039 (10) |
N2 | 0.0204 (11) | 0.0205 (11) | 0.0268 (12) | −0.0038 (9) | −0.0012 (9) | −0.0006 (9) |
C1 | 0.0160 (12) | 0.0212 (12) | 0.0253 (12) | 0.0025 (10) | 0.0079 (10) | −0.0026 (10) |
C2 | 0.0163 (12) | 0.0258 (14) | 0.0381 (15) | −0.0049 (11) | 0.0101 (11) | −0.0089 (12) |
C3 | 0.0112 (12) | 0.0430 (17) | 0.0382 (16) | −0.0015 (12) | 0.0018 (11) | −0.0154 (13) |
C4 | 0.0152 (12) | 0.0395 (17) | 0.0313 (15) | 0.0069 (11) | 0.0002 (11) | −0.0045 (13) |
C5 | 0.0185 (12) | 0.0235 (13) | 0.0278 (13) | 0.0035 (10) | 0.0050 (10) | −0.0007 (11) |
C6 | 0.0140 (11) | 0.0219 (12) | 0.0220 (12) | −0.0008 (9) | 0.0057 (9) | −0.0013 (10) |
C7 | 0.0100 (11) | 0.0188 (12) | 0.0225 (12) | 0.0029 (9) | 0.0026 (9) | 0.0022 (9) |
C8 | 0.0144 (12) | 0.0275 (14) | 0.0242 (13) | 0.0028 (10) | −0.0004 (10) | −0.0030 (10) |
C9 | 0.0211 (13) | 0.0400 (17) | 0.0214 (13) | 0.0066 (12) | 0.0004 (10) | 0.0007 (12) |
C10 | 0.0278 (14) | 0.0325 (16) | 0.0282 (14) | 0.0090 (12) | 0.0086 (12) | 0.0095 (12) |
C11 | 0.0214 (13) | 0.0206 (13) | 0.0333 (14) | 0.0022 (11) | 0.0068 (11) | 0.0029 (11) |
C12 | 0.0114 (11) | 0.0212 (12) | 0.0244 (12) | 0.0028 (9) | 0.0038 (9) | −0.0009 (10) |
S1—C6 | 1.771 (3) | C4—C5 | 1.388 (4) |
S1—S2 | 2.0687 (9) | C4—H4A | 0.97 (3) |
S2—C7 | 1.765 (3) | C5—C6 | 1.400 (4) |
N1—C1 | 1.392 (4) | C5—H5A | 0.94 (3) |
N1—H1N1 | 0.87 (4) | C7—C8 | 1.396 (4) |
N1—H2N1 | 0.91 (4) | C7—C12 | 1.416 (3) |
N2—C12 | 1.388 (3) | C8—C9 | 1.384 (4) |
N2—H1N2 | 0.86 (4) | C8—H8A | 1.00 (3) |
N2—H2N2 | 0.88 (3) | C9—C10 | 1.386 (4) |
C1—C2 | 1.405 (4) | C9—H9A | 0.96 (3) |
C1—C6 | 1.407 (4) | C10—C11 | 1.386 (4) |
C2—C3 | 1.383 (4) | C10—H10A | 0.93 (3) |
C2—H2A | 0.98 (3) | C11—C12 | 1.397 (4) |
C3—C4 | 1.388 (4) | C11—H11A | 0.97 (3) |
C3—H3A | 0.95 (4) | ||
C6—S1—S2 | 103.87 (9) | C6—C5—H5A | 119 (2) |
C7—S2—S1 | 103.05 (8) | C5—C6—C1 | 120.5 (2) |
C1—N1—H1N1 | 115 (3) | C5—C6—S1 | 119.7 (2) |
C1—N1—H2N1 | 113 (2) | C1—C6—S1 | 119.8 (2) |
H1N1—N1—H2N1 | 112 (3) | C8—C7—C12 | 120.2 (2) |
C12—N2—H1N2 | 116 (2) | C8—C7—S2 | 119.9 (2) |
C12—N2—H2N2 | 115 (2) | C12—C7—S2 | 119.74 (19) |
H1N2—N2—H2N2 | 113 (3) | C9—C8—C7 | 120.9 (3) |
N1—C1—C2 | 120.8 (3) | C9—C8—H8A | 120.6 (18) |
N1—C1—C6 | 121.0 (2) | C7—C8—H8A | 118.4 (18) |
C2—C1—C6 | 118.1 (3) | C8—C9—C10 | 119.0 (3) |
C3—C2—C1 | 120.4 (3) | C8—C9—H9A | 121.3 (18) |
C3—C2—H2A | 120 (2) | C10—C9—H9A | 119.7 (18) |
C1—C2—H2A | 119 (2) | C9—C10—C11 | 121.2 (3) |
C2—C3—C4 | 121.6 (3) | C9—C10—H10A | 121 (2) |
C2—C3—H3A | 119 (2) | C11—C10—H10A | 118 (2) |
C4—C3—H3A | 119 (2) | C10—C11—C12 | 120.7 (3) |
C5—C4—C3 | 118.7 (3) | C10—C11—H11A | 121.7 (19) |
C5—C4—H4A | 119 (2) | C12—C11—H11A | 117.6 (19) |
C3—C4—H4A | 122 (2) | N2—C12—C11 | 121.0 (2) |
C4—C5—C6 | 120.7 (3) | N2—C12—C7 | 120.9 (2) |
C4—C5—H5A | 120 (2) | C11—C12—C7 | 118.0 (2) |
C6—S1—S2—C7 | −89.29 (13) | S1—S2—C7—C8 | 99.8 (2) |
N1—C1—C2—C3 | 176.9 (2) | S1—S2—C7—C12 | −84.50 (19) |
C6—C1—C2—C3 | −0.4 (4) | C12—C7—C8—C9 | 0.1 (4) |
C1—C2—C3—C4 | 0.1 (4) | S2—C7—C8—C9 | 175.7 (2) |
C2—C3—C4—C5 | 0.2 (4) | C7—C8—C9—C10 | 0.6 (4) |
C3—C4—C5—C6 | −0.3 (4) | C8—C9—C10—C11 | −0.7 (4) |
C4—C5—C6—C1 | 0.0 (4) | C9—C10—C11—C12 | 0.1 (4) |
C4—C5—C6—S1 | 177.7 (2) | C10—C11—C12—N2 | 179.6 (3) |
N1—C1—C6—C5 | −177.0 (2) | C10—C11—C12—C7 | 0.5 (4) |
C2—C1—C6—C5 | 0.3 (4) | C8—C7—C12—N2 | −179.7 (2) |
N1—C1—C6—S1 | 5.4 (3) | S2—C7—C12—N2 | 4.7 (3) |
C2—C1—C6—S1 | −177.36 (19) | C8—C7—C12—C11 | −0.6 (3) |
S2—S1—C6—C5 | 98.6 (2) | S2—C7—C12—C11 | −176.27 (19) |
S2—S1—C6—C1 | −83.8 (2) |
Cg1 and Cg2 are the centroids for C7–C12 and C1–C16 phenyl rings, respectively. |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1N1···N2i | 0.87 (4) | 2.39 (4) | 3.222 (3) | 160 (4) |
N2—H1N2···N1ii | 0.86 (4) | 2.39 (4) | 3.184 (3) | 155 (3) |
N2—H2N2···S1iii | 0.88 (4) | 2.61 (3) | 3.436 (2) | 156 (3) |
C4—H4A···Cg1iv | 0.97 (3) | 2.95 (3) | 3.689 (3) | 134 (2) |
C9—H9A···Cg2v | 0.96 (3) | 2.89 (3) | 3.637 (3) | 135 (2) |
Symmetry codes: (i) −x, y+1/2, −z+1/2; (ii) −x−1/2, y−1/2, z; (iii) x−1/2, y, −z+1/2; (iv) x+1, y, z; (v) −x, −y+1, −z+1. |
Experimental details
Crystal data | |
Chemical formula | C12H12N2S2 |
Mr | 248.36 |
Crystal system, space group | Orthorhombic, Pbca |
Temperature (K) | 100 |
a, b, c (Å) | 8.2531 (1), 13.0278 (2), 22.3655 (4) |
V (Å3) | 2404.73 (6) |
Z | 8 |
Radiation type | Mo Kα |
µ (mm−1) | 0.42 |
Crystal size (mm) | 0.23 × 0.18 × 0.17 |
Data collection | |
Diffractometer | Bruker SMART APEXII CCD area-detector diffractometer |
Absorption correction | Multi-scan (SADABS; Bruker, 2009) |
Tmin, Tmax | 0.912, 0.934 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 47724, 2750, 2417 |
Rint | 0.040 |
(sin θ/λ)max (Å−1) | 0.650 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.048, 0.124, 1.19 |
No. of reflections | 2750 |
No. of parameters | 193 |
H-atom treatment | All H-atom parameters refined |
Δρmax, Δρmin (e Å−3) | 0.50, −0.43 |
Computer programs: APEX2 (Bruker, 2009), SAINT (Bruker, 2009), SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).
Cg1 and Cg2 are the centroids for C7–C12 and C1–C16 phenyl rings, respectively. |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1N1···N2i | 0.87 (4) | 2.39 (4) | 3.222 (3) | 160 (4) |
N2—H1N2···N1ii | 0.86 (4) | 2.39 (4) | 3.184 (3) | 155 (3) |
N2—H2N2···S1iii | 0.88 (4) | 2.61 (3) | 3.436 (2) | 156 (3) |
C4—H4A···Cg1iv | 0.97 (3) | 2.95 (3) | 3.689 (3) | 134 (2) |
C9—H9A···Cg2v | 0.96 (3) | 2.89 (3) | 3.637 (3) | 135 (2) |
Symmetry codes: (i) −x, y+1/2, −z+1/2; (ii) −x−1/2, y−1/2, z; (iii) x−1/2, y, −z+1/2; (iv) x+1, y, z; (v) −x, −y+1, −z+1. |
Acknowledgements
HKF and JHG thank Universiti Sains Malaysia (USM) for the Research University Golden Goose grant (No. 1001/PFIZIK/811012). JHG also thanks USM for the award of a USM fellowship.
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Nitrogen- and sulphur- containing compounds are important intermediates in the synthesis of various heterocyclic compounds. Ortho amino thiophenols are important precursors in the preparation of a variety of heterocycles such as benzothiadiazepines, thiadiazoles, thiadiazines etc. (Kalluraya et al., 2000; Kalluraya & Chimbalkar, 2001). The title compound was obtained during an attempt to study the aerial oxidation of aminothiophenols. Molecular and crystal structures of thioamide derivatives have been analyzed (Garbarczyk et al., 1999).
A search of the November 2008 release of the Cambridge Structural Database (Allen, 2002) reveals that the room temperature crystal structures of the title compound (Fig. 1) were first reported with R = 0.057 for 369 reflections (Gomes de Mesquita, 1967), then followed with R = 0.086 for 1313 reflections (Lee & Bryant, 1970) and R = 0.042 (Ribar et al., 1975). The current redetermination at 100 K increases significantly the precision of the structural and geometrical parameters and provides a lower R value (R = 0.048 based on 2750 independent observed reflections).
Comparison with the previously reported unit cell parameters (Ribar et al., 1975) reveals that on cooling to 100 K, a expands by 0.41 %, whereas b and c contract by 1.15 and 1.74 %, respectively. This can be explained by the fact that along the c axis, the molecules are interconnected by weak C—H···π interactions only whereas along the a and b axes, the molecules are interconnected by the stronger hydrogen bonds (Figs 2 & 3, Table 1). The previously reported structure (Lee & Bryant, 1970) suggests two intramolecular N—H···S hydrogen bonds, but the current work observes no such intramolecular hydrogen bonds with bond angle larger than 120°. The bond lengths are comparable to but more precise than the previously reported structures (Lee & Bryant, 1970; Ribar et al., 1975).
In the crystal structure, molecules are linked into two-dimensional frameworks parallel to the ab plane (Fig. 3) rather than one-dimensional infinite chains as reported previously (Lee & Bryant, 1970). Based on freely refined hydrogen atom positions, an additional intermolecular N2—H2N2···S1 hydrogen bond (Table 1) has also been established. Intermolecular C4—H4A···Cg1 and C9—H9A···Cg2 interactions (Table 1) further stabilize the crystal structure.