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Mol­ecules of the title compound, C8H11NOS, are flat and almost Cs-symmetric. Bond lengths and angles resemble calculated values at the B3LYP/6-311+G(2 d,p) level of theory. The solid is characterized by van der Waals bonding and π stacking (stacking distance = 3.352 Å) of the basic motif of the structure: planar centrosymmetric dimers that are bonded by pairs of symmetry-equivalent N—H...S bonds. The dimer structure is rationalized by the nature of the hydrogen-bond acceptor orbital, the S(3p) orbital located in the mol­ecular plane. The double-donor–double-acceptor situation in the dimer results in an unusual C=S...H angle of about 127° which is large compared with isolated C=S...H bonds (circa 100°), but small compared with the almost linear acceptor geometry in related oxo compounds.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536807047599/bt2521sup1.cif
Contains datablocks I, global

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S1600536807047599/bt2521Isup2.hkl
Contains datablock I

CCDC reference: 667280

Key indicators

  • Single-crystal X-ray study
  • T = 200 K
  • Mean [sigma](C-C)= 0.002 Å
  • R factor = 0.041
  • wR factor = 0.118
  • Data-to-parameter ratio = 18.2

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Comment top

The title compound, C8H11NOS, was prepared as the parent acid of a potentially chelating ligand.

The flat molecules of the title compound combine to centrosymmetric dimers by means of two hydrogen bonds of the N—H···S=C type (Figure 2). The dimeric structure reflects the nature of the hydrogen-bond acceptor orbital at the sulfur atom: one of the sulfur lone pairs – the HOMO of the molecule which, in terms of an NBO analysis, exhibits S(3p) character – is the best suited acceptor orbital in terms of hydrogen-bond strength. This orbital lies in the molecular plane, perpendicular to the C=S axis. Almost flat dimers thus have to be expected with H···S=C angles close to 90°. Accordingly, the dimers are flat. The C=S···H angle, however, is unusually obtuse (127°) compared with the expectation values [approx. 90° from frontier-orbital considerations, approx. 100° as the experimental mean value, compare with Allen et al. (1997)]. The reason is the double-donor-double-acceptor situation in the dimer. The smaller the acceptor angle, the closer the repulsive N—H···H—N contact. The experimentally determined 127° angle is thus a compromise (note a somewhat different view on the dimer by counting the intramolecular H···S contact despite the small N—H···S angle of 108° as a hydrogen bond as well, ending up with bifurcated bonds). Though the acceptor angle is unusually large for a sulfur compound, it is much smaller than the acceptor angle in related oxo compounds due to the different acceptor-orbital situation in the oxo case (Ramos Silva et al., 2007).

The packing of the dimers is determined by van-der-Waals forces. Figure 3 shows the stacking of the flat molecules. The normal distance of the molecular planes is 3.352 Å and thus resembles the typical 3.4-Å distance of π-stacked nucleic bases. However, the typical partial overlap of the DNA azaaromates (Voet et al., 1999) is not observed in (I). Instead, a close perpendicular contact is found for a single ring atom only (C4). Figure 4 shows this situation in a normal view. The figure suggests that, possibly, the methyl groups prohibit a more extended π-stacking-type contact.

Related literature top

The title compound was prepared according to a modified procedure as previously described by Plater et al. (2002).

A recent analysis, including an identification of the acceptor lone pair and the considerable strength of hydrogen bonds to sulfur acceptors, has been published by Wennmohs et al. (2003) who use the NBO method as the localization algorithm. The metric aspects of hydrogen bonding to CS acceptors have been reviewed by Allen et al. (1997). The structure of a related, dimer-forming oxo analogue has recently been reported by Ramos Silva et al. (2007). A related N—H···SC-linked, but non-centrosymmetric, dimer has been found for a morpholine-dithione derivative (Linden et al., 2001).

For related literature, see: Voet et al. (1999).

Experimental top

The title compound, C8H11NOS, was prepared upon the reaction of thiophosgene with 3,3'-dimethylpyrrole in diethylether under ice cooling, subsequent heat up to room temperature, and quenching of the reaction products with methanol after 30 minutes' reaction time. Subsequent workup with column chromatography on silica with chloroform as the mobile phase yielded pale yellow crystals. Sublimation of the raw product yielded colourless crystals of the title compound.

Refinement top

All H atoms were located in a difference map. C-bonded H atoms were refined as riding on their parent atoms. One common isotropic displacement parameter for the methyl-H atoms was refined, individual U values were refined for the methylidine-H and the N-bonded H. The positional parameters of the N-bonded H atom were refined freely.

Structure description top

The title compound, C8H11NOS, was prepared as the parent acid of a potentially chelating ligand.

The flat molecules of the title compound combine to centrosymmetric dimers by means of two hydrogen bonds of the N—H···S=C type (Figure 2). The dimeric structure reflects the nature of the hydrogen-bond acceptor orbital at the sulfur atom: one of the sulfur lone pairs – the HOMO of the molecule which, in terms of an NBO analysis, exhibits S(3p) character – is the best suited acceptor orbital in terms of hydrogen-bond strength. This orbital lies in the molecular plane, perpendicular to the C=S axis. Almost flat dimers thus have to be expected with H···S=C angles close to 90°. Accordingly, the dimers are flat. The C=S···H angle, however, is unusually obtuse (127°) compared with the expectation values [approx. 90° from frontier-orbital considerations, approx. 100° as the experimental mean value, compare with Allen et al. (1997)]. The reason is the double-donor-double-acceptor situation in the dimer. The smaller the acceptor angle, the closer the repulsive N—H···H—N contact. The experimentally determined 127° angle is thus a compromise (note a somewhat different view on the dimer by counting the intramolecular H···S contact despite the small N—H···S angle of 108° as a hydrogen bond as well, ending up with bifurcated bonds). Though the acceptor angle is unusually large for a sulfur compound, it is much smaller than the acceptor angle in related oxo compounds due to the different acceptor-orbital situation in the oxo case (Ramos Silva et al., 2007).

The packing of the dimers is determined by van-der-Waals forces. Figure 3 shows the stacking of the flat molecules. The normal distance of the molecular planes is 3.352 Å and thus resembles the typical 3.4-Å distance of π-stacked nucleic bases. However, the typical partial overlap of the DNA azaaromates (Voet et al., 1999) is not observed in (I). Instead, a close perpendicular contact is found for a single ring atom only (C4). Figure 4 shows this situation in a normal view. The figure suggests that, possibly, the methyl groups prohibit a more extended π-stacking-type contact.

The title compound was prepared according to a modified procedure as previously described by Plater et al. (2002).

A recent analysis, including an identification of the acceptor lone pair and the considerable strength of hydrogen bonds to sulfur acceptors, has been published by Wennmohs et al. (2003) who use the NBO method as the localization algorithm. The metric aspects of hydrogen bonding to CS acceptors have been reviewed by Allen et al. (1997). The structure of a related, dimer-forming oxo analogue has recently been reported by Ramos Silva et al. (2007). A related N—H···SC-linked, but non-centrosymmetric, dimer has been found for a morpholine-dithione derivative (Linden et al., 2001).

For related literature, see: Voet et al. (1999).

Computing details top

Data collection: COLLECT (Nonius, 2004); cell refinement: SCALEPACK (Otwinowski & Minor, 1997); data reduction: SCALEPACK and DENZO (Otwinowski & Minor, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEPIII (Burnett & Johnson, 1996); software used to prepare material for publication: SHELXL97 (Sheldrick, 1997).

Figures top
[Figure 1] Fig. 1. The molecular structure of (I), with atom labels and anisotropic displacement ellipsoids (drawn at 50% probability level) for non-H atoms.
[Figure 2] Fig. 2. N—H···S-bonded dimers. The contour of the S(3p) acceptor orbital from an NBO analysis on a single molecule of (I) is drawn at an isovalue of 0.02.
[Figure 3] Fig. 3. π stacking along [101], projected down [0 1 0].
[Figure 4] Fig. 4. Closest contact of the aromatic rings in a centrosymmetric pair of molecules of adjacent stacks in a normal view.
O-methyl 3,4-dimethylpyrrole-2-thiocarboxylate top
Crystal data top
C8H11NOSF(000) = 360
Mr = 169.24Dx = 1.298 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 15311 reflections
a = 7.4399 (2) Åθ = 3.1–27.5°
b = 13.9413 (5) ŵ = 0.32 mm1
c = 8.4118 (2) ÅT = 200 K
β = 96.928 (2)°Block, colourless
V = 866.12 (4) Å30.25 × 0.21 × 0.18 mm
Z = 4
Data collection top
Nonius KappaCCD
diffractometer
1724 reflections with I > 2σ(I)
Radiation source: rotating anodeRint = 0.015
MONTEL, graded multilayered X-ray optics monochromatorθmax = 27.5°, θmin = 3.8°
CCD; rotation images; thick slices scansh = 99
3806 measured reflectionsk = 1817
1980 independent reflectionsl = 1010
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.041Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.118Only H-atom displacement parameters refined
S = 1.10 w = 1/[σ2(Fo2) + (0.0618P)2 + 0.2807P]
where P = (Fo2 + 2Fc2)/3
1980 reflections(Δ/σ)max < 0.001
109 parametersΔρmax = 0.33 e Å3
0 restraintsΔρmin = 0.29 e Å3
Crystal data top
C8H11NOSV = 866.12 (4) Å3
Mr = 169.24Z = 4
Monoclinic, P21/cMo Kα radiation
a = 7.4399 (2) ŵ = 0.32 mm1
b = 13.9413 (5) ÅT = 200 K
c = 8.4118 (2) Å0.25 × 0.21 × 0.18 mm
β = 96.928 (2)°
Data collection top
Nonius KappaCCD
diffractometer
1724 reflections with I > 2σ(I)
3806 measured reflectionsRint = 0.015
1980 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0410 restraints
wR(F2) = 0.118Only H-atom displacement parameters refined
S = 1.10Δρmax = 0.33 e Å3
1980 reflectionsΔρmin = 0.29 e Å3
109 parameters
Special details top

Refinement. The refU entry for H-atom refinement summarizes: individual U for the single C-bonded H, one common U for the methyl-Hs. All H-atom parameters refined for the N-bonded H.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
S0.45898 (6)0.33388 (3)0.54208 (6)0.04671 (18)
O0.68081 (15)0.20285 (8)0.44864 (14)0.0402 (3)
N0.73885 (19)0.45490 (10)0.39510 (17)0.0379 (3)
H70.658 (3)0.4848 (15)0.435 (3)0.048 (6)*
C10.7642 (2)0.35680 (11)0.39575 (18)0.0324 (3)
C20.9182 (2)0.33903 (10)0.31993 (18)0.0329 (3)
C30.9836 (2)0.42870 (11)0.27372 (19)0.0367 (3)
C40.8693 (2)0.49803 (12)0.3232 (2)0.0408 (4)
H40.88100.56520.30870.054 (6)*
C51.0016 (2)0.24411 (12)0.2895 (2)0.0405 (4)
H510.90720.19970.24340.097 (3)*
H521.06080.21790.39060.097 (3)*
H531.09150.25250.21450.097 (3)*
C61.1463 (2)0.44705 (14)0.1889 (2)0.0482 (4)
H611.16550.51630.18100.097 (3)*
H621.12660.41930.08120.097 (3)*
H631.25310.41750.24910.097 (3)*
C70.6373 (2)0.29558 (11)0.46148 (18)0.0331 (3)
C80.5583 (2)0.13178 (13)0.4981 (2)0.0457 (4)
H810.44320.13490.42810.097 (3)*
H820.53690.14420.60890.097 (3)*
H830.61140.06780.49090.097 (3)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
S0.0442 (3)0.0386 (3)0.0618 (3)0.00333 (17)0.0247 (2)0.00071 (18)
O0.0395 (6)0.0279 (6)0.0560 (7)0.0006 (4)0.0165 (5)0.0023 (5)
N0.0409 (7)0.0272 (7)0.0481 (8)0.0021 (5)0.0153 (6)0.0026 (6)
C10.0348 (7)0.0260 (7)0.0367 (7)0.0016 (6)0.0062 (6)0.0008 (5)
C20.0349 (7)0.0299 (7)0.0340 (7)0.0018 (6)0.0047 (6)0.0011 (6)
C30.0380 (8)0.0330 (8)0.0403 (8)0.0015 (6)0.0093 (6)0.0009 (6)
C40.0453 (9)0.0274 (7)0.0516 (9)0.0024 (6)0.0140 (7)0.0018 (6)
C50.0396 (8)0.0332 (8)0.0500 (9)0.0067 (6)0.0104 (7)0.0020 (7)
C60.0451 (9)0.0466 (10)0.0563 (10)0.0021 (8)0.0202 (8)0.0057 (8)
C70.0342 (7)0.0312 (7)0.0341 (7)0.0008 (6)0.0043 (6)0.0005 (6)
C80.0456 (9)0.0325 (8)0.0618 (11)0.0076 (7)0.0176 (8)0.0040 (8)
Geometric parameters (Å, º) top
S—C71.6498 (16)C3—C61.499 (2)
O—C71.3403 (19)C4—H40.9500
O—C81.441 (2)C5—H510.9800
N—C41.346 (2)C5—H520.9800
N—C11.381 (2)C5—H530.9800
N—H70.84 (2)C6—H610.9800
C1—C21.399 (2)C6—H620.9800
C1—C71.432 (2)C6—H630.9800
C2—C31.413 (2)C8—H810.9800
C2—C51.497 (2)C8—H820.9800
C3—C41.385 (2)C8—H830.9800
C7—O—C8118.20 (13)C2—C5—H53109.5
C4—N—C1109.80 (14)H51—C5—H53109.5
C4—N—H7123.6 (14)H52—C5—H53109.5
C1—N—H7126.6 (14)C3—C6—H61109.5
N—C1—C2107.02 (13)C3—C6—H62109.5
N—C1—C7119.71 (14)H61—C6—H62109.5
C2—C1—C7133.22 (14)C3—C6—H63109.5
C1—C2—C3107.27 (13)H61—C6—H63109.5
C1—C2—C5127.87 (14)H62—C6—H63109.5
C3—C2—C5124.85 (15)O—C7—C1111.52 (13)
C4—C3—C2106.88 (14)O—C7—S124.00 (12)
C4—C3—C6125.78 (15)C1—C7—S124.48 (12)
C2—C3—C6127.34 (15)O—C8—H81109.5
N—C4—C3109.02 (14)O—C8—H82109.5
N—C4—H4125.5H81—C8—H82109.5
C3—C4—H4125.5O—C8—H83109.5
C2—C5—H51109.5H81—C8—H83109.5
C2—C5—H52109.5H82—C8—H83109.5
H51—C5—H52109.5
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N—H7···Si0.84 (2)2.69 (2)3.3622 (15)138.7 (18)
Symmetry code: (i) x+1, y+1, z+1.

Experimental details

Crystal data
Chemical formulaC8H11NOS
Mr169.24
Crystal system, space groupMonoclinic, P21/c
Temperature (K)200
a, b, c (Å)7.4399 (2), 13.9413 (5), 8.4118 (2)
β (°) 96.928 (2)
V3)866.12 (4)
Z4
Radiation typeMo Kα
µ (mm1)0.32
Crystal size (mm)0.25 × 0.21 × 0.18
Data collection
DiffractometerNonius KappaCCD
Absorption correction
No. of measured, independent and
observed [I > 2σ(I)] reflections
3806, 1980, 1724
Rint0.015
(sin θ/λ)max1)0.649
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.041, 0.118, 1.10
No. of reflections1980
No. of parameters109
H-atom treatmentOnly H-atom displacement parameters refined
Δρmax, Δρmin (e Å3)0.33, 0.29

Computer programs: COLLECT (Nonius, 2004), SCALEPACK (Otwinowski & Minor, 1997), SCALEPACK and DENZO (Otwinowski & Minor, 1997), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), ORTEPIII (Burnett & Johnson, 1996).

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N—H7···Si0.84 (2)2.69 (2)3.3622 (15)138.7 (18)
Symmetry code: (i) x+1, y+1, z+1.
 

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