Azinyl Sulfides. LXVII. 1-Methyl­pyridine-4(1H)-thione

The title compound, C₆H₇NS, is planar, with endo-C-N-C bond angles of 118.7 (2) and 118.8 (2)°, and C-S bond lengths of 1.697 (2) and 1.692 (2) Å for the two symmetrically independent mol­ecules. 1-Methylpyridinium-4-thiol­ate is the major contributor to the molecular structure in the solid state.

S1. Comment

Insight into the nature of the thiocarbonyl group in thiolactams is important, i.e. for the evaluation of biological significance of pyrimidinethiones and pyrimidine-dithiones as rare-bases in RNA or purinethiones (e.g. thioguanine) as anticancer drugs (Reynolds, 1989). The synthetic application of thiolactams also seems to depend on their structural features. Due to electronic interactions expressed by mesomerism of the thiocarbonyl group in thioamides: the length of carbon sulfur bonds in thioamides are a little longer than those in thiones (Rozsondai, 1993) and vary from 1.622 (2) Å in thiocarbonylo-1,1'-bis(2-methylbenzimidazole) (II) (Dolling et al., 1995) to 1.692 (2) or 1.698 (2) Å in 2(1H)-pyridinethione (III) (Ohms et al., 1982), or from 1.677 (3) Å up to 1.691 (4) Å for 3-substituted 1-methyl-2(1H)-pyridinethiones (IVa,b) (Dupont et al., 1983, Dupont et al., 1984). γ-azinethiones can be considered as vinylogous analogs of thiolactams. Several papers deal with the study on dibenzo- and benzo-γ-pyridinethiones, i.e. on derivatives of 9(10H)-acridinethione (VI) (Jaud et al., 1995) or 4(1H)-quinolinethione (V) (Maślankiewicz et al., 1998), respectively. This paper presents the data for the parent γ-pyridinethione as exemplified by the title 1-methyl-4(1H)-pyridinethione (I).

The atom-numbering scheme is shown in the ORTEPII drawing in Fig. 1 (Johnson, 1976) with selected bond lengths and angles are given in Table 1. There are two symmetrically independent molecules in the unit cell which exhibit similar values of bond lengths and angles at the 2σ level. The pyridine rings of (I) are planar for both independent molecules (r.m.s. deviations of the ring atoms are 0.004 (3) and 0.005 (3) Å for molecules A and B, respectively); exo-substituents S41A, C11A and S41B are in plane of the appropriate rings within 3σ except for C11B which deviates out of the plane by 0.030 (4) Å. The two planar molecules are inclined by the angle 67.75 (7)°. There is one intermolecular C—H···π interaction between molecules A and B, C5B—H5B···(N1A/C2A/C3A/C4A/C5A/C6A)ⁱ and a H···Cg distance of 2.69 Å where Cg1 is the aromatic ring centroid and symmetry operator (i) = -1 - x,2y,1 - z.

The most interesting molecular feature of (I) is the planarity around the endocyclic-N atom indicating sp² hybridization of the N1 atom. Thus, the planar tricoordinated N1 atom should bear a positive charge and, furthermore, a pyridinium-type resonance form (Ia) should be the major contributor to the true molecular structure of (I).

It is well known (Witanowski et al., 1973) that a N atom bearing a formal positive charge tends to produce a relatively sharp ¹⁴N NMR signal. In fact the ¹⁴N NMR spectrum (in CDCl₃ solution) of the title compound 1-methyl-4(1H)-pyridinethione (I) reveals an N atom signal at δ = -220 p.p.m. with half-height of linewidths Δν_1/2 = 286 Hz (Zi\,eba & Maślankiewicz, 1996). It has led us to the conclusion that for compound (I), a pyridinium-type resonance form (Ia) is the major contributor to the real molecular structure of (I). The occurrence of a positively charged endocyclic N atom should be accompanied by elongation of the C–S bond of the thiocarbonyl group as shown in formula (Ia). However, the value of the the endocyclic C–N–C bond angle of 118.7 (2) and 118.8 (2)° in (I) is below the generally accepted limit (120°) (Pauling, 1960) for the endocyclic C–N–C bond angle in pyridinium salts.

S2. Experimental

Compound (1) was synthesized and purified by the method of Albert & Barlin (1959). Single crystals suitable for X-ray data collection were obtained on slow evaporation from a ethyl acetate solution.

S3. Refinement

The H atoms were treated as riding atoms using the SHELXL97 (Sheldrick, 1997) defaults, d(C—H) = 0.93 Å for the aromatic and 0.96 Å for methyl-H atoms.

Computing details

Data collection: CAD-4 Software (Enraf-Nonius, 1989); cell refinement: CAD-4 Software (Enraf-Nonius, 1989); data reduction: SDP (B. A. Frenz & Associates Inc., 1985); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEPII (Johnson, 1976); software used to prepare material for publication: SHELXL97 (Sheldrick, 1997).

Figures

SCHEME 1 SCHEME 2 Fig. 1. Molecular structures of the two symmetrically independent molecules of compound (I) at the 50% probability level (Farrugia, 1997). SCHEME 3

'1-Methyl-4(1H)-pyridinethione'

Crystal data

C6H7NS	Z = 4
Mr = 125.19	F(000) = 264
Triclinic, P1	Dx = 1.312 Mg m^−3
a = 7.544 (1) Å	Cu Kα radiation, λ = 1.54178 Å
b = 9.085 (1) Å	Cell parameters from 25 reflections
c = 9.302 (1) Å	θ = 7–19°
α = 89.84 (1)°	µ = 3.59 mm^−1
β = 84.03 (1)°	T = 293 K
γ = 87.98 (1)°	Block, yellow
V = 633.7 (1) Å^3	0.32 × 0.28 × 0.26 mm

Data collection

Enraf-Nonius CAD4 diffractometer	Rint = 0.022
Radiation source: fine-focus sealed tube	θmax = 78.2°, θmin = 4.8°
Graphite monochromator	h = 0→9
ω–2θ scans	k = −11→11
2861 measured reflections	l = −11→11
2654 independent reflections	3 standard reflections every 60 min
2012 reflections with I > 2σ(I)	intensity decay: <1%

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)] = 0.046	H-atom parameters constrained
wR(F^2) = 0.135	w = 1/[σ^2(Fo^2) + (0.0893P)^2 + 0.0559P] where P = (Fo^2 + 2Fc^2)/3
S = 1.04	(Δ/σ)max = 0.018
2654 reflections	Δρmax = 0.47 e Å^−3
148 parameters	Δρmin = −0.37 e Å^−3
0 restraints	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.012 (2)

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
N1A	−0.2188 (2)	0.64031 (19)	0.38365 (18)	0.0449 (4)
C2A	−0.0653 (3)	0.6837 (2)	0.4314 (2)	0.0474 (5)
H2A	−0.0708	0.7490	0.5087	0.057*
C3A	0.0951 (3)	0.6346 (2)	0.3697 (2)	0.0471 (4)
H3A	0.1974	0.6665	0.4061	0.057*
C4A	0.1131 (3)	0.5359 (2)	0.2512 (2)	0.0429 (4)
C5A	−0.0512 (3)	0.4955 (2)	0.2038 (2)	0.0522 (5)
H5A	−0.0503	0.4318	0.1256	0.063*
C6A	−0.2091 (3)	0.5474 (2)	0.2697 (3)	0.0532 (5)
H6A	−0.3141	0.5183	0.2356	0.064*
S41A	0.31282 (8)	0.47185 (6)	0.17014 (7)	0.0587 (2)
C11A	−0.3913 (3)	0.6968 (3)	0.4530 (3)	0.0637 (6)
H11A	−0.4856	0.6602	0.4028	0.095*
H11B	−0.3951	0.8025	0.4498	0.095*
H11C	−0.4062	0.6648	0.5519	0.095*
N1B	−0.7288 (2)	0.9911 (2)	1.10807 (17)	0.0470 (4)
C2B	−0.6816 (3)	0.8587 (2)	1.0474 (2)	0.0512 (5)
H2B	−0.6389	0.7839	1.1044	0.061*
C3B	−0.6946 (3)	0.8321 (2)	0.9061 (2)	0.0512 (5)
H3B	−0.6583	0.7401	0.8680	0.061*
C4B	−0.7621 (3)	0.9408 (2)	0.8143 (2)	0.0435 (4)
C5B	−0.8102 (3)	1.0766 (2)	0.8837 (2)	0.0494 (5)
H5B	−0.8557	1.1531	0.8304	0.059*
C6B	−0.7923 (3)	1.0991 (2)	1.0248 (2)	0.0505 (5)
H6B	−0.8244	1.1908	1.0657	0.061*
S41B	−0.78108 (9)	0.91137 (8)	0.63710 (6)	0.0669 (2)
C11B	−0.7161 (4)	1.0181 (4)	1.2623 (2)	0.0708 (7)
H11D	−0.8287	1.0005	1.3164	0.106*
H11E	−0.6852	1.1184	1.2758	0.106*
H11F	−0.6259	0.9531	1.2956	0.106*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
N1A	0.0404 (9)	0.0451 (8)	0.0498 (9)	−0.0043 (7)	−0.0076 (7)	−0.0022 (7)
C2A	0.0496 (11)	0.0475 (10)	0.0469 (10)	−0.0056 (8)	−0.0125 (8)	−0.0079 (8)
C3A	0.0440 (10)	0.0464 (10)	0.0534 (10)	−0.0059 (8)	−0.0149 (8)	−0.0066 (8)
C4A	0.0429 (10)	0.0363 (8)	0.0510 (10)	−0.0043 (7)	−0.0107 (8)	0.0003 (7)
C5A	0.0494 (12)	0.0508 (10)	0.0586 (12)	−0.0065 (9)	−0.0138 (9)	−0.0164 (9)
C6A	0.0447 (11)	0.0547 (11)	0.0631 (12)	−0.0091 (9)	−0.0161 (9)	−0.0116 (9)
S41A	0.0464 (3)	0.0529 (3)	0.0766 (4)	0.0024 (2)	−0.0067 (2)	−0.0151 (2)
C11A	0.0464 (12)	0.0706 (15)	0.0726 (15)	0.0004 (11)	0.0000 (10)	−0.0113 (12)
N1B	0.0467 (9)	0.0561 (10)	0.0389 (8)	−0.0082 (7)	−0.0058 (7)	−0.0029 (7)
C2B	0.0515 (12)	0.0478 (10)	0.0553 (11)	−0.0024 (9)	−0.0102 (9)	0.0078 (9)
C3B	0.0542 (12)	0.0382 (9)	0.0609 (12)	0.0005 (8)	−0.0059 (9)	−0.0084 (8)
C4B	0.0411 (10)	0.0477 (10)	0.0419 (9)	−0.0083 (8)	−0.0038 (7)	−0.0060 (7)
C5B	0.0590 (12)	0.0409 (9)	0.0485 (10)	0.0002 (9)	−0.0074 (9)	0.0022 (8)
C6B	0.0587 (12)	0.0420 (9)	0.0502 (11)	−0.0028 (9)	−0.0027 (9)	−0.0090 (8)
S41B	0.0719 (4)	0.0870 (5)	0.0437 (3)	−0.0132 (3)	−0.0108 (2)	−0.0170 (3)
C11B	0.0709 (16)	0.102 (2)	0.0407 (11)	−0.0151 (15)	−0.0086 (10)	−0.0077 (12)

Geometric parameters (Å, º)

N1A—C6A	1.351 (3)	N1B—C2B	1.351 (3)
N1A—C2A	1.354 (3)	N1B—C6B	1.353 (3)
N1A—C11A	1.468 (3)	N1B—C11B	1.470 (3)
C2A—C3A	1.346 (3)	C2B—C3B	1.351 (3)
C2A—H2A	0.9300	C2B—H2B	0.9300
C3A—C4A	1.415 (3)	C3B—C4B	1.419 (3)
C3A—H3A	0.9300	C3B—H3B	0.9300
C4A—C5A	1.418 (3)	C4B—C5B	1.412 (3)
C4A—S41A	1.697 (2)	C4B—S41B	1.6922 (19)
C5A—C6A	1.352 (3)	C5B—C6B	1.350 (3)
C5A—H5A	0.9300	C5B—H5B	0.9300
C6A—H6A	0.9300	C6B—H6B	0.9300
C11A—H11A	0.9600	C11B—H11D	0.9600
C11A—H11B	0.9600	C11B—H11E	0.9600
C11A—H11C	0.9600	C11B—H11F	0.9600
C6A—N1A—C2A	118.71 (19)	C2B—N1B—C6B	118.80 (17)
C6A—N1A—C11A	121.21 (19)	C2B—N1B—C11B	121.2 (2)
C2A—N1A—C11A	120.07 (19)	C6B—N1B—C11B	120.0 (2)
C3A—C2A—N1A	121.57 (18)	N1B—C2B—C3B	121.77 (19)
C3A—C2A—H2A	119.2	N1B—C2B—H2B	119.1
N1A—C2A—H2A	119.2	C3B—C2B—H2B	119.1
C2A—C3A—C4A	122.11 (18)	C2B—C3B—C4B	121.76 (19)
C2A—C3A—H3A	118.9	C2B—C3B—H3B	119.1
C4A—C3A—H3A	118.9	C4B—C3B—H3B	119.1
C3A—C4A—C5A	114.18 (19)	C5B—C4B—C3B	113.95 (18)
C3A—C4A—S41A	123.53 (16)	C5B—C4B—S41B	122.90 (16)
C5A—C4A—S41A	122.29 (15)	C3B—C4B—S41B	123.14 (15)
C6A—C5A—C4A	121.52 (19)	C6B—C5B—C4B	122.29 (19)
C6A—C5A—H5A	119.2	C6B—C5B—H5B	118.9
C4A—C5A—H5A	119.2	C4B—C5B—H5B	118.9
N1A—C6A—C5A	121.90 (19)	C5B—C6B—N1B	121.40 (18)
N1A—C6A—H6A	119.1	C5B—C6B—H6B	119.3
C5A—C6A—H6A	119.1	N1B—C6B—H6B	119.3
N1A—C11A—H11A	109.5	N1B—C11B—H11D	109.5
N1A—C11A—H11B	109.5	N1B—C11B—H11E	109.5
H11A—C11A—H11B	109.5	H11D—C11B—H11E	109.5
N1A—C11A—H11C	109.5	N1B—C11B—H11F	109.5
H11A—C11A—H11C	109.5	H11D—C11B—H11F	109.5
H11B—C11A—H11C	109.5	H11E—C11B—H11F	109.5
C6A—N1A—C2A—C3A	−1.1 (3)	C6B—N1B—C2B—C3B	0.6 (3)
C11A—N1A—C2A—C3A	−179.6 (2)	C11B—N1B—C2B—C3B	179.3 (2)
N1A—C2A—C3A—C4A	0.4 (3)	N1B—C2B—C3B—C4B	−1.3 (4)
C2A—C3A—C4A—C5A	0.5 (3)	C2B—C3B—C4B—C5B	0.9 (3)
C2A—C3A—C4A—S41A	179.83 (16)	C2B—C3B—C4B—S41B	−179.77 (18)
C3A—C4A—C5A—C6A	−0.7 (3)	C3B—C4B—C5B—C6B	0.1 (3)
S41A—C4A—C5A—C6A	179.92 (18)	S41B—C4B—C5B—C6B	−179.19 (18)
C2A—N1A—C6A—C5A	0.9 (3)	C4B—C5B—C6B—N1B	−0.8 (4)
C11A—N1A—C6A—C5A	179.4 (2)	C2B—N1B—C6B—C5B	0.5 (3)
C4A—C5A—C6A—N1A	0.1 (4)	C11B—N1B—C6B—C5B	−178.2 (2)