5-Methylsulfanyl-1
H-tetrazole, C
2H
4N
4S, crystallizes in dimorphic forms; the α-form crystallizes at room temperature in the monoclinic crystal system, space group
P2
1/
m, and the β-form crystallizes by sublimation at 423 K in the orthorhombic crystal system, space group
Pbcm. In both forms, the molecules occupy crystallographic mirror planes and are connected to one another
via N—H
N hydrogen bonds, the amino H atoms being disordered. The two forms differ from one another in their packing; there are polar layers in the α-form and non-polar layers in the β-form.
Supporting information
CCDC references: 231068; 231069
Compound (I) was obtained from a commercial source (Aldrich) and was used without further purification. Crystals of the α-form were grown from an ethanol solution. Crystals of the β-form were prepared by sublimation of the α-form at 423 K for 0.5 h. The sublimate was recrystallized at once from an ethanol solution, to give colorless prisms of the β-form.
The amino H atoms in both forms are disordered, and these atoms were refined as riding on? the relevent N atoms. The occupancy factors of the H atoms in the α-form were refined at the initial stages. When the occupancies were found to be equal, they were fixed at 0.5. For the β-form, the occupancy factors of the amino H atoms were refined to 0.8 and 0.2. The methyl H atoms in the β-form were found to be disordered between two equally distributed conformations.
For both compounds, data collection: Collect (Nonius, 2000); cell refinement: DENZO SMN (Otwinowski & Minor 1997); data reduction: DENZO SMN; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997).
(Ia) 5-Methylsulfanyl-1
H-tetrazole (
α-form)
top
Crystal data top
C2H4N4S | F(000) = 120 |
Mr = 116.15 | Dx = 1.625 Mg m−3 |
Monoclinic, P21/m | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2yb | Cell parameters from 828 reflections |
a = 5.041 (1) Å | θ = 2.8–25.5° |
b = 6.547 (1) Å | µ = 0.54 mm−1 |
c = 7.247 (1) Å | T = 293 K |
β = 96.98 (2)° | Prism, colorless |
V = 237.40 (7) Å3 | 0.51 × 0.30 × 0.24 mm |
Z = 2 | |
Data collection top
Nonius KappaCCD diffractometer | 419 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.015 |
Graphite monochromator | θmax = 25.5°, θmin = 2.8° |
Detector resolution: 95 pixels mm-1 | h = −6→6 |
ϕ scan | k = −6→7 |
828 measured reflections | l = −8→8 |
479 independent reflections | |
Refinement top
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.029 | H atoms treated by a mixture of independent and constrained refinement |
wR(F2) = 0.069 | w = 1/[σ2(Fo2) + (0.0448P)2] where P = (Fo2 + 2Fc2)/3 |
S = 1.10 | (Δ/σ)max < 0.001 |
479 reflections | Δρmax = 0.19 e Å−3 |
51 parameters | Δρmin = −0.28 e Å−3 |
0 restraints | Extinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 2.18 (12) |
Crystal data top
C2H4N4S | V = 237.40 (7) Å3 |
Mr = 116.15 | Z = 2 |
Monoclinic, P21/m | Mo Kα radiation |
a = 5.041 (1) Å | µ = 0.54 mm−1 |
b = 6.547 (1) Å | T = 293 K |
c = 7.247 (1) Å | 0.51 × 0.30 × 0.24 mm |
β = 96.98 (2)° | |
Data collection top
Nonius KappaCCD diffractometer | 419 reflections with I > 2σ(I) |
828 measured reflections | Rint = 0.015 |
479 independent reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.029 | 0 restraints |
wR(F2) = 0.069 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.10 | Δρmax = 0.19 e Å−3 |
479 reflections | Δρmin = −0.28 e Å−3 |
51 parameters | |
Special details top
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 (Å2) top | x | y | z | Uiso*/Ueq | Occ. (<1) |
S1 | 0.90212 (10) | 0.2500 | 0.36836 (7) | 0.0404 (3) | |
N1 | 0.6360 (3) | 0.2500 | 0.0208 (3) | 0.0393 (5) | |
H1N | 0.4801 | 0.2500 | 0.0575 | 0.059* | 0.50 |
N2 | 0.6903 (4) | 0.2500 | −0.1592 (3) | 0.0455 (5) | |
N3 | 0.9450 (4) | 0.2500 | −0.1599 (3) | 0.0422 (5) | |
N4 | 1.0634 (4) | 0.2500 | 0.0187 (3) | 0.0347 (5) | |
H4N | 1.2325 | 0.2500 | 0.0543 | 0.052* | 0.50 |
C1 | 0.8695 (4) | 0.2500 | 0.1291 (3) | 0.0307 (5) | |
C2 | 1.2587 (4) | 0.2500 | 0.4184 (3) | 0.0420 (6) | |
H21 | 1.333 (3) | 0.133 (3) | 0.368 (2) | 0.063 (5)* | |
H22 | 1.301 (4) | 0.2500 | 0.555 (4) | 0.048 (7)* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
S1 | 0.0264 (4) | 0.0652 (5) | 0.0300 (4) | 0.000 | 0.0045 (2) | 0.000 |
N1 | 0.0309 (11) | 0.0494 (10) | 0.0361 (12) | 0.000 | −0.0019 (8) | 0.000 |
N2 | 0.0401 (12) | 0.0602 (11) | 0.0343 (11) | 0.000 | −0.0032 (9) | 0.000 |
N3 | 0.0432 (12) | 0.0512 (10) | 0.0321 (11) | 0.000 | 0.0039 (9) | 0.000 |
N4 | 0.0337 (9) | 0.0382 (9) | 0.0328 (11) | 0.000 | 0.0067 (8) | 0.000 |
C1 | 0.0277 (10) | 0.0331 (9) | 0.0307 (12) | 0.000 | 0.0012 (9) | 0.000 |
C2 | 0.0275 (12) | 0.0608 (14) | 0.0365 (15) | 0.000 | −0.0013 (10) | 0.000 |
Geometric parameters (Å, º) top
S1—C1 | 1.722 (2) | N3—N4 | 1.358 (3) |
S1—C2 | 1.790 (2) | N4—C1 | 1.336 (3) |
N1—C1 | 1.333 (3) | N4—H4N | 0.8600 |
N1—N2 | 1.365 (3) | C2—H21 | 0.946 (18) |
N1—H1N | 0.8600 | C2—H22 | 0.99 (3) |
N2—N3 | 1.285 (3) | | |
| | | |
C1—S1—C2 | 100.05 (10) | N3—N4—H4N | 126.2 |
C1—N1—N2 | 107.34 (18) | N1—C1—N4 | 107.8 (2) |
C1—N1—H1N | 126.3 | N1—C1—S1 | 124.23 (18) |
N2—N1—H1N | 126.3 | N4—C1—S1 | 128.01 (17) |
N3—N2—N1 | 108.65 (17) | S1—C2—H21 | 111.0 (10) |
N2—N3—N4 | 108.69 (19) | S1—C2—H22 | 106.9 (14) |
C1—N4—N3 | 107.57 (18) | H21—C2—H22 | 109.9 (12) |
C1—N4—H4N | 126.2 | | |
| | | |
C1—N1—N2—N3 | 0.0 | N3—N4—C1—N1 | 0.0 |
N1—N2—N3—N4 | 0.0 | N3—N4—C1—S1 | 180.0 |
N2—N3—N4—C1 | 0.0 | C2—S1—C1—N1 | 180.0 |
N2—N1—C1—N4 | 0.0 | C2—S1—C1—N4 | 0.0 |
N2—N1—C1—S1 | 180.0 | | |
(Ib) 5-Methylsulfanyl-1
H-tetrazole (
β-form)
top
Crystal data top
C2H4N4S | F(000) = 240 |
Mr = 116.15 | Dx = 1.523 Mg m−3 |
Orthorhombic, Pbcm | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2c 2b | Cell parameters from 827 reflections |
a = 7.714 (2) Å | θ = 2.6–25.0° |
b = 9.833 (2) Å | µ = 0.50 mm−1 |
c = 6.679 (1) Å | T = 293 K |
V = 506.61 (18) Å3 | Plate, colorless |
Z = 4 | 0.36 × 0.21 × 0.15 mm |
Data collection top
Nonius KappaCCD diffractometer | 336 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.024 |
Graphite monochromator | θmax = 25.0°, θmin = 2.6° |
Detector resolution: 95 pixels mm-1 | h = −9→9 |
ϕ scan | k = −11→11 |
827 measured reflections | l = −7→7 |
484 independent reflections | |
Refinement top
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)] = 0.031 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.067 | H-atom parameters constrained |
S = 0.95 | w = 1/[σ2(Fo2) + (0.0337P)2] where P = (Fo2 + 2Fc2)/3 |
484 reflections | (Δ/σ)max < 0.001 |
45 parameters | Δρmax = 0.13 e Å−3 |
0 restraints | Δρmin = −0.23 e Å−3 |
Crystal data top
C2H4N4S | V = 506.61 (18) Å3 |
Mr = 116.15 | Z = 4 |
Orthorhombic, Pbcm | Mo Kα radiation |
a = 7.714 (2) Å | µ = 0.50 mm−1 |
b = 9.833 (2) Å | T = 293 K |
c = 6.679 (1) Å | 0.36 × 0.21 × 0.15 mm |
Data collection top
Nonius KappaCCD diffractometer | 336 reflections with I > 2σ(I) |
827 measured reflections | Rint = 0.024 |
484 independent reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.031 | 0 restraints |
wR(F2) = 0.067 | H-atom parameters constrained |
S = 0.95 | Δρmax = 0.13 e Å−3 |
484 reflections | Δρmin = −0.23 e Å−3 |
45 parameters | |
Special details top
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 (Å2) top | x | y | z | Uiso*/Ueq | Occ. (<1) |
S1 | 0.31157 (10) | 0.11585 (7) | 0.2500 | 0.0650 (3) | |
N1 | −0.0301 (3) | 0.1820 (2) | 0.2500 | 0.0511 (6) | |
H1N | −0.0106 | 0.2681 | 0.2500 | 0.077* | 0.79 (3) |
N2 | −0.1892 (3) | 0.1228 (2) | 0.2500 | 0.0594 (7) | |
N3 | −0.1628 (2) | −0.0058 (2) | 0.2500 | 0.0534 (6) | |
N4 | 0.0101 (3) | −0.0341 (2) | 0.2500 | 0.0457 (6) | |
H4N | 0.0569 | −0.1134 | 0.2500 | 0.069* | 0.21 (3) |
C1 | 0.0922 (3) | 0.0843 (2) | 0.2500 | 0.0431 (7) | |
C2 | 0.3906 (3) | −0.0567 (3) | 0.2500 | 0.0676 (9) | |
H2A | 0.3424 | −0.1049 | 0.3620 | 0.101* | 0.50 |
H2B | 0.5147 | −0.0563 | 0.2601 | 0.101* | 0.50 |
H2C | 0.3567 | −0.1009 | 0.1279 | 0.101* | 0.50 |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
S1 | 0.0545 (5) | 0.0526 (5) | 0.0880 (7) | −0.0172 (3) | 0.000 | 0.000 |
N1 | 0.0585 (14) | 0.0334 (12) | 0.0613 (16) | −0.0031 (11) | 0.000 | 0.000 |
N2 | 0.0551 (15) | 0.0414 (16) | 0.0818 (18) | 0.0058 (10) | 0.000 | 0.000 |
N3 | 0.0424 (14) | 0.0444 (16) | 0.0733 (18) | −0.0011 (10) | 0.000 | 0.000 |
N4 | 0.0479 (12) | 0.0320 (14) | 0.0571 (16) | −0.0033 (9) | 0.000 | 0.000 |
C1 | 0.0526 (15) | 0.0325 (14) | 0.0441 (18) | −0.0048 (13) | 0.000 | 0.000 |
C2 | 0.0416 (15) | 0.067 (2) | 0.094 (3) | 0.0018 (13) | 0.000 | 0.000 |
Geometric parameters (Å, º) top
S1—C1 | 1.721 (2) | N3—N4 | 1.363 (3) |
S1—C2 | 1.803 (3) | N4—C1 | 1.325 (3) |
N1—C1 | 1.346 (3) | N4—H4N | 0.8600 |
N1—N2 | 1.358 (3) | C2—H2A | 0.9600 |
N1—H1N | 0.8600 | C2—H2B | 0.9600 |
N2—N3 | 1.281 (3) | C2—H2C | 0.9600 |
| | | |
C1—S1—C2 | 99.37 (11) | N4—C1—N1 | 107.0 (2) |
C1—N1—N2 | 109.1 (2) | N4—C1—S1 | 129.0 (2) |
C1—N1—H1N | 125.4 | N1—C1—S1 | 124.09 (19) |
N2—N1—H1N | 125.4 | S1—C2—H2A | 109.5 |
N3—N2—N1 | 106.2 (2) | S1—C2—H2B | 109.5 |
N2—N3—N4 | 110.9 (2) | H2A—C2—H2B | 109.5 |
C1—N4—N3 | 106.78 (19) | S1—C2—H2C | 109.5 |
C1—N4—H4N | 126.6 | H2A—C2—H2C | 109.5 |
N3—N4—H4N | 126.6 | H2B—C2—H2C | 109.5 |
| | | |
C1—N1—N2—N3 | 0.0 | N2—N1—C1—N4 | 0.0 |
N1—N2—N3—N4 | 0.0 | N2—N1—C1—S1 | 180.0 |
N2—N3—N4—C1 | 0.0 | C2—S1—C1—N4 | 0.0 |
N3—N4—C1—N1 | 0.0 | C2—S1—C1—N1 | 180.0 |
N3—N4—C1—S1 | 180.0 | | |
Experimental details
| (Ia) | (Ib) |
Crystal data |
Chemical formula | C2H4N4S | C2H4N4S |
Mr | 116.15 | 116.15 |
Crystal system, space group | Monoclinic, P21/m | Orthorhombic, Pbcm |
Temperature (K) | 293 | 293 |
a, b, c (Å) | 5.041 (1), 6.547 (1), 7.247 (1) | 7.714 (2), 9.833 (2), 6.679 (1) |
α, β, γ (°) | 90, 96.98 (2), 90 | 90, 90, 90 |
V (Å3) | 237.40 (7) | 506.61 (18) |
Z | 2 | 4 |
Radiation type | Mo Kα | Mo Kα |
µ (mm−1) | 0.54 | 0.50 |
Crystal size (mm) | 0.51 × 0.30 × 0.24 | 0.36 × 0.21 × 0.15 |
|
Data collection |
Diffractometer | Nonius KappaCCD diffractometer | Nonius KappaCCD diffractometer |
Absorption correction | – | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 828, 479, 419 | 827, 484, 336 |
Rint | 0.015 | 0.024 |
(sin θ/λ)max (Å−1) | 0.606 | 0.595 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.029, 0.069, 1.10 | 0.031, 0.067, 0.95 |
No. of reflections | 479 | 484 |
No. of parameters | 51 | 45 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.19, −0.28 | 0.13, −0.23 |
Comparison of selected geometric parameters in the dimorphs of (I) (Å, °) top | α-form (I) | β-form (II) |
S1-C1 | 1.722 (2) | 1.721 (2) |
S1-C2 | 1.790 (2) | 1.803 (3) |
N1-C1 | 1.333 (3) | 1.346 (3) |
N1-N2 | 1.365 (3) | 1.358 (3) |
N2-N3 | 1.285 (3) | 1.281 (3) |
N3-N4 | 1.358 (3) | 1.363 (3) |
N4-C1 | 1.336 (3) | 1.325 (3) |
| | |
| α-form (I) | β-form (II) |
C1-S1-C2 | 100.1 (1) | 99.4 (1) |
C1-N1-N2 | 107.3 (2) | 109.1 (2) |
N3-N2-N1 | 108.7 (2) | 106.2 (2) |
N2-N3-N4 | 108.7 (2) | 110.9 (2) |
C1-N4-N3 | 107.6 (2) | 106.8 (2) |
N1-C1-N4 | 107.8 (2) | 107.0 (2) |
N1-C1-S1 | 124.2 (2) | 124.1 (2) |
N4-C1-S1 | 128.0 (2) | 129.0 (2) |
Hydrogen-bond geometry (Å, °) in the dimorphs of (I) topD—H···A | D—H | H···A | D···A | D—H···A |
α-form (I) | | | | |
N1-H1N···N4i | 0.86 | 2.08 | 2.885 (3) | 154 |
N4-H4N···N1ii | 0.86 | 2.08 | 2.885 (3) | 156 |
| | | | |
β-form (II) | | | | |
N1-H1N···N4iii | 0.86 | 1.95 | 2.797 (3) | 170 |
N4-H4N···N1iv | 0.86 | 2.02 | 2.797 (3) | 149 |
Symmetry codes: (i) x − 1, y, z; (ii) x + 1, y, z; (iii) −x, y + 1/2, z; (iv) −x, y − 1/2, z. |
Tetrazoles are acidic heterocycles that are deprotonated under physiological conditions and serve routinely as bioisosteric replacements for carboxylic acids in modern drug design (Kraft et al., 2002). The title compound, (I), decomposes upon heating at or slightly above its melting point, as do other 5-substituted mercaptotetrazoles. There are two known routes for the decomposition of (I). Lieber & Enkoji (1961) reported that 5-substituted mercaptotetrazoles undergo decomposition, at or near their melting points, to hydrazoic acid and the corresponding thiocyanate. Kroto & Suffolk (1972) and Solouki et al. (1976) reported that (I) decomposes mainly through the elimination of thioformaldehyde and the formation of tetrazale, which is split into an N atom?, cyanamide and carbodiimide.
Compound (I) has been examined because of its ability to undergo methyl rearrangement in the solid or in the liquid state (Kaftory & Handelsman-Benory, 1994, Handelsman-Benory et al., 2000, Greenberg et al. 2001, Kaftory et al., 2001, Kaftory, 2002).
Compound (I) crystallizes in dimorphic forms, viz. the α-form, (Iα), in space group P21/m, and the β-form, (Iβ), in space group Pbcm. The thermal behavior of (Iα) is indicated by the DSC thermograph shown in Fig. 1. The first small endothermic peak (at 382 K), with a measured enthalpy of 1.81 kJ mol−1, is assigned to a phase transition to the β-form. The second endothermic peak (at 425 K, ΔH = 13.10 kJ mol−1) is assigned to the melting point, and the last exothermic peak (at 429 K, ΔH = −33.65 kJ mol−1) is assigned to the decomposition of the compound. The thermal behavior of (Iβ) is indicated by the DSC thermograph shown in Fig. 2. The endothermic peak at 424 K (ΔH = 13.65 kJ mol−1) is assigned to the melting point, and the exothermic peak at 430 K (ΔH = −33.65 kJ mol−1) is assigned to the decomposition of the compound. The phase transition from the α-form to the β-form is reversible, although the reverse transition from the β- to the α-form could not be observed in the DSC thermograph because it takes about an hour. However, when the high temperature phase was left to stand for an hour the endotherm at 382 K was observed, thus indicating α-form formation.
Both dimorphs have layer structures, in which the molecules occupy crystallographic mirror sites. The molecules within the layers are connected to one another by N—H···N hydrogen bonds (Table 2, and Figs. 3 and 4). The dimorphs differ in the way that the molecules are arranged within the layers. In the α-form, a crystallographic center of inversion lies between the layers, and the molecules within the layer are arranged in parallel rows, so that the layer is polar. In the β-form, each second row is reversed, and therefore the layer is non-polar. In both forms, the amino H atoms are disordered. They are disordered equally between two sites in the α form, which fact is reflected in equivalence? of the N1—C1 and N4—C1 bond lengths (Table 1). In the β-form, the amino H atoms are distributed unevenly, with occupancy factors of 0.8 and 1/5, and the N—C1? bond lengths are significantly different (Table 1).