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5-Methyl­sulfanyl-1H-tetrazole, C2H4N4S, crystallizes in dimor­phic forms; the α-form crystallizes at room temperature in the monoclinic crystal system, space group P21/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

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270103022704/av1152sup1.cif
Contains datablocks Ia, Ib, global

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270103022704/av1152Iasup2.hkl
Contains datablock Ia

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270103022704/av1152Ibsup3.hkl
Contains datablock Ib

CCDC references: 231068; 231069

Comment top

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).

Experimental top

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.

Refinement top

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.

Computing details top

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).

Figures top
[Figure 1]
[Figure 2]
[Figure 3]
[Figure 4]
Figure 1. A DSC thermogram for the α-form of (I) (heating rate 5° min−1, weight of sample 7.8 mg).

Figure 2. A DSC thermogram for the β-form of (I) (heating rate 5° min−1, weight of sample 6.8 mg).

Figure 3. A layer of molecules in the structure of the α-form of (I). Only one of the disordered H atoms is shown. Displacement ellipsoids for non-H atoms are drawn at the 50% probability level.

Figure 4. A layer of molecules in the structure of the β-form of (I). Only one of the disordered H atoms is shown. Dispalcement ellipsoids for non-H atoms are drawn at the 50% probability level.

Table 1. Comparison of selected geometric parameters in the dimorphs of (I) (Å, °).

Table 2. Hydrogen-bonding geometry (Å, °) in the dimorphs of (I).
(Ia) 5-Methylsulfanyl-1H-tetrazole (α-form) top
Crystal data top
C2H4N4SF(000) = 120
Mr = 116.15Dx = 1.625 Mg m3
Monoclinic, P21/mMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybCell parameters from 828 reflections
a = 5.041 (1) Åθ = 2.8–25.5°
b = 6.547 (1) ŵ = 0.54 mm1
c = 7.247 (1) ÅT = 293 K
β = 96.98 (2)°Prism, colorless
V = 237.40 (7) Å30.51 × 0.30 × 0.24 mm
Z = 2
Data collection top
Nonius KappaCCD
diffractometer
419 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.015
Graphite monochromatorθmax = 25.5°, θmin = 2.8°
Detector resolution: 95 pixels mm-1h = 66
ϕ scank = 67
828 measured reflectionsl = 88
479 independent reflections
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.029H 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 reflectionsΔρmax = 0.19 e Å3
51 parametersΔρmin = 0.28 e Å3
0 restraintsExtinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 2.18 (12)
Crystal data top
C2H4N4SV = 237.40 (7) Å3
Mr = 116.15Z = 2
Monoclinic, P21/mMo Kα radiation
a = 5.041 (1) ŵ = 0.54 mm1
b = 6.547 (1) ÅT = 293 K
c = 7.247 (1) Å0.51 × 0.30 × 0.24 mm
β = 96.98 (2)°
Data collection top
Nonius KappaCCD
diffractometer
419 reflections with I > 2σ(I)
828 measured reflectionsRint = 0.015
479 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0290 restraints
wR(F2) = 0.069H atoms treated by a mixture of independent and constrained refinement
S = 1.10Δρmax = 0.19 e Å3
479 reflectionsΔρmin = 0.28 e Å3
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
xyzUiso*/UeqOcc. (<1)
S10.90212 (10)0.25000.36836 (7)0.0404 (3)
N10.6360 (3)0.25000.0208 (3)0.0393 (5)
H1N0.48010.25000.05750.059*0.50
N20.6903 (4)0.25000.1592 (3)0.0455 (5)
N30.9450 (4)0.25000.1599 (3)0.0422 (5)
N41.0634 (4)0.25000.0187 (3)0.0347 (5)
H4N1.23250.25000.05430.052*0.50
C10.8695 (4)0.25000.1291 (3)0.0307 (5)
C21.2587 (4)0.25000.4184 (3)0.0420 (6)
H211.333 (3)0.133 (3)0.368 (2)0.063 (5)*
H221.301 (4)0.25000.555 (4)0.048 (7)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
S10.0264 (4)0.0652 (5)0.0300 (4)0.0000.0045 (2)0.000
N10.0309 (11)0.0494 (10)0.0361 (12)0.0000.0019 (8)0.000
N20.0401 (12)0.0602 (11)0.0343 (11)0.0000.0032 (9)0.000
N30.0432 (12)0.0512 (10)0.0321 (11)0.0000.0039 (9)0.000
N40.0337 (9)0.0382 (9)0.0328 (11)0.0000.0067 (8)0.000
C10.0277 (10)0.0331 (9)0.0307 (12)0.0000.0012 (9)0.000
C20.0275 (12)0.0608 (14)0.0365 (15)0.0000.0013 (10)0.000
Geometric parameters (Å, º) top
S1—C11.722 (2)N3—N41.358 (3)
S1—C21.790 (2)N4—C11.336 (3)
N1—C11.333 (3)N4—H4N0.8600
N1—N21.365 (3)C2—H210.946 (18)
N1—H1N0.8600C2—H220.99 (3)
N2—N31.285 (3)
C1—S1—C2100.05 (10)N3—N4—H4N126.2
C1—N1—N2107.34 (18)N1—C1—N4107.8 (2)
C1—N1—H1N126.3N1—C1—S1124.23 (18)
N2—N1—H1N126.3N4—C1—S1128.01 (17)
N3—N2—N1108.65 (17)S1—C2—H21111.0 (10)
N2—N3—N4108.69 (19)S1—C2—H22106.9 (14)
C1—N4—N3107.57 (18)H21—C2—H22109.9 (12)
C1—N4—H4N126.2
C1—N1—N2—N30.0N3—N4—C1—N10.0
N1—N2—N3—N40.0N3—N4—C1—S1180.0
N2—N3—N4—C10.0C2—S1—C1—N1180.0
N2—N1—C1—N40.0C2—S1—C1—N40.0
N2—N1—C1—S1180.0
(Ib) 5-Methylsulfanyl-1H-tetrazole (β-form) top
Crystal data top
C2H4N4SF(000) = 240
Mr = 116.15Dx = 1.523 Mg m3
Orthorhombic, PbcmMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2c 2bCell parameters from 827 reflections
a = 7.714 (2) Åθ = 2.6–25.0°
b = 9.833 (2) ŵ = 0.50 mm1
c = 6.679 (1) ÅT = 293 K
V = 506.61 (18) Å3Plate, colorless
Z = 40.36 × 0.21 × 0.15 mm
Data collection top
Nonius KappaCCD
diffractometer
336 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.024
Graphite monochromatorθmax = 25.0°, θmin = 2.6°
Detector resolution: 95 pixels mm-1h = 99
ϕ scank = 1111
827 measured reflectionsl = 77
484 independent reflections
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)] = 0.031Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.067H-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 parametersΔρmax = 0.13 e Å3
0 restraintsΔρmin = 0.23 e Å3
Crystal data top
C2H4N4SV = 506.61 (18) Å3
Mr = 116.15Z = 4
Orthorhombic, PbcmMo Kα radiation
a = 7.714 (2) ŵ = 0.50 mm1
b = 9.833 (2) ÅT = 293 K
c = 6.679 (1) Å0.36 × 0.21 × 0.15 mm
Data collection top
Nonius KappaCCD
diffractometer
336 reflections with I > 2σ(I)
827 measured reflectionsRint = 0.024
484 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0310 restraints
wR(F2) = 0.067H-atom parameters constrained
S = 0.95Δρmax = 0.13 e Å3
484 reflectionsΔρmin = 0.23 e Å3
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
xyzUiso*/UeqOcc. (<1)
S10.31157 (10)0.11585 (7)0.25000.0650 (3)
N10.0301 (3)0.1820 (2)0.25000.0511 (6)
H1N0.01060.26810.25000.077*0.79 (3)
N20.1892 (3)0.1228 (2)0.25000.0594 (7)
N30.1628 (2)0.0058 (2)0.25000.0534 (6)
N40.0101 (3)0.0341 (2)0.25000.0457 (6)
H4N0.05690.11340.25000.069*0.21 (3)
C10.0922 (3)0.0843 (2)0.25000.0431 (7)
C20.3906 (3)0.0567 (3)0.25000.0676 (9)
H2A0.34240.10490.36200.101*0.50
H2B0.51470.05630.26010.101*0.50
H2C0.35670.10090.12790.101*0.50
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
S10.0545 (5)0.0526 (5)0.0880 (7)0.0172 (3)0.0000.000
N10.0585 (14)0.0334 (12)0.0613 (16)0.0031 (11)0.0000.000
N20.0551 (15)0.0414 (16)0.0818 (18)0.0058 (10)0.0000.000
N30.0424 (14)0.0444 (16)0.0733 (18)0.0011 (10)0.0000.000
N40.0479 (12)0.0320 (14)0.0571 (16)0.0033 (9)0.0000.000
C10.0526 (15)0.0325 (14)0.0441 (18)0.0048 (13)0.0000.000
C20.0416 (15)0.067 (2)0.094 (3)0.0018 (13)0.0000.000
Geometric parameters (Å, º) top
S1—C11.721 (2)N3—N41.363 (3)
S1—C21.803 (3)N4—C11.325 (3)
N1—C11.346 (3)N4—H4N0.8600
N1—N21.358 (3)C2—H2A0.9600
N1—H1N0.8600C2—H2B0.9600
N2—N31.281 (3)C2—H2C0.9600
C1—S1—C299.37 (11)N4—C1—N1107.0 (2)
C1—N1—N2109.1 (2)N4—C1—S1129.0 (2)
C1—N1—H1N125.4N1—C1—S1124.09 (19)
N2—N1—H1N125.4S1—C2—H2A109.5
N3—N2—N1106.2 (2)S1—C2—H2B109.5
N2—N3—N4110.9 (2)H2A—C2—H2B109.5
C1—N4—N3106.78 (19)S1—C2—H2C109.5
C1—N4—H4N126.6H2A—C2—H2C109.5
N3—N4—H4N126.6H2B—C2—H2C109.5
C1—N1—N2—N30.0N2—N1—C1—N40.0
N1—N2—N3—N40.0N2—N1—C1—S1180.0
N2—N3—N4—C10.0C2—S1—C1—N40.0
N3—N4—C1—N10.0C2—S1—C1—N1180.0
N3—N4—C1—S1180.0

Experimental details

(Ia)(Ib)
Crystal data
Chemical formulaC2H4N4SC2H4N4S
Mr116.15116.15
Crystal system, space groupMonoclinic, P21/mOrthorhombic, Pbcm
Temperature (K)293293
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), 9090, 90, 90
V3)237.40 (7)506.61 (18)
Z24
Radiation typeMo KαMo Kα
µ (mm1)0.540.50
Crystal size (mm)0.51 × 0.30 × 0.240.36 × 0.21 × 0.15
Data collection
DiffractometerNonius KappaCCD
diffractometer
Nonius KappaCCD
diffractometer
Absorption correction
No. of measured, independent and
observed [I > 2σ(I)] reflections
828, 479, 419 827, 484, 336
Rint0.0150.024
(sin θ/λ)max1)0.6060.595
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.029, 0.069, 1.10 0.031, 0.067, 0.95
No. of reflections479484
No. of parameters5145
H-atom treatmentH atoms treated by a mixture of independent and constrained refinementH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.19, 0.280.13, 0.23

Computer programs: Collect (Nonius, 2000), DENZO SMN (Otwinowski & Minor 1997), DENZO SMN, SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), ORTEP-3 for Windows (Farrugia, 1997).

Comparison of selected geometric parameters in the dimorphs of (I) (Å, °) top
α-form (I)β-form (II)
S1-C11.722 (2)1.721 (2)
S1-C21.790 (2)1.803 (3)
N1-C11.333 (3)1.346 (3)
N1-N21.365 (3)1.358 (3)
N2-N31.285 (3)1.281 (3)
N3-N41.358 (3)1.363 (3)
N4-C11.336 (3)1.325 (3)
α-form (I)β-form (II)
C1-S1-C2100.1 (1)99.4 (1)
C1-N1-N2107.3 (2)109.1 (2)
N3-N2-N1108.7 (2)106.2 (2)
N2-N3-N4108.7 (2)110.9 (2)
C1-N4-N3107.6 (2)106.8 (2)
N1-C1-N4107.8 (2)107.0 (2)
N1-C1-S1124.2 (2)124.1 (2)
N4-C1-S1128.0 (2)129.0 (2)
Hydrogen-bond geometry (Å, °) in the dimorphs of (I) top
D—H···AD—HH···AD···AD—H···A
α-form (I)
N1-H1N···N4i0.862.082.885 (3)154
N4-H4N···N1ii0.862.082.885 (3)156
β-form (II)
N1-H1N···N4iii0.861.952.797 (3)170
N4-H4N···N1iv0.862.022.797 (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.
 

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