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Acta Cryst. (2009). E65, o126    [ doi:10.1107/S1600536808042165 ]

3-Phenyl-1H-1,2,4-triazol-5-amine-5-phenyl-1H-1,2,4-triazol-3-amine (1/1)

A. V. Dolzhenko, G. K. Tan, L. L. Koh, A. V. Dolzhenko and W. K. Chui

Abstract top

In the title compound, C8H8N4·C8H8N4, two tautomers, viz. 3-phenyl-1,2,4-triazol-5-amine and 5-phenyl-1,2,4-triazol-3-amine, are crystallized together in equal amounts. The 3-phenyl-1,2,4-triazol-5-amine molecule is essentially planar; the phenyl ring makes a dihedral angle of 2.3 (2)° with the mean plane of the 1,2,4-triazole ring. In the 5-phenyl-1,2,4-triazol-3-amine tautomer, the mean planes of the phenyl and 1,2,4-triazole rings form a dihedral angle of 30.8 (2)°. The [pi]-electron delocalization of the amino group with the 1,2,4-triazole nucleus in the 3-phenyl-1,2,4-triazol-5-amine molecule is more extensive than that in the 5-phenyl-1,2,4-triazol-3-amine tautomer. The molecules are linked into a two-dimensional network parallel to (100) by N-H...N hydrogen bonds.

Comment top

1,2,4-Triazol-5-amines have been used as building blocks for the synthesis of fused heterocyclic systems, e.g. 1,2,4-triazolo[1,5-a]pyrimidines (Fischer, 2007) and 1,2,4-triazolo[1,5-a][1,3,5]triazines (Dolzhenko et al., 2006). Herein, we report the structural study of 3(5)-phenyl-1,2,4-triazol-5(3)-amine, which was used as a synthon in our previous works (Dolzhenko et al., 2007a,b).

Due to annular tautomerism in 1,2,4-triazole ring, there is a theoretical possibility of three tautomeric forms, namely 3-phenyl-1,2,4-triazol-5-amine (I), 5-phenyl-1,2,4-triazol-3-amine (II), and 5-phenyl-4H-1,2,4-triazol-3-amine (III) (Fig.1).

Usually, tautomerizable 1,2,4-triazoles with nonequivalent substituents at positions 3 and 5 crystallize as a tautomer bearing at position 5 substituent with relatively more pronounced electronodonor properties (Buzykin et al., 2006). Considering significant difference in electronic properties of phenyl and amino group, the crystal would be assembled from the molecules of tautomer I analogously to the reported 3-pyridin-2-yl-1,2,4-triazol-5-amine (Dolzhenko et al., 2009). Surprisingly, two tautomeric forms I and II were found crystallized together in the crystal. To the best of our knowledge, this is the first example of existence in crystal of unequally 3,5-disubstituted tautomerizable 1,2,4-triazole tautomeric form with electronodonor group located at position 3.

The geometry of the tautomer I molecule is essentially planar (Fig.2). The amino group is involved in π-electron delocalization with the 1,2,4-triazole nucleus. It is almost planar with small deviation 0.06 (2) Å of the nitrogen atom from the C8/H4A/H4B plane. The length of the C8—N4 bond is 1.337 (3) Å. The π-electron delocalization of the amino group of II with the 1,2,4-triazole nucleus is significantly lower. The nitrogen atom (N8) of the amino group adopts a pyramidal configuration with 0.21 (2) Å deviation of the nitrogen atom from the C16/H8A/H8B plane. The C16—N8 bond [1.372 (3) Å] is also longer. The phenyl ring of I makes a small dihedral angle of 2.3 (2)° with the mean plane of the 1,2,4-triazole ring. The molecule of tautomer II loses this planarity. The mean planes of the phenyl and 1,2,4-triazole rings of II form a dihedral angle of 30.8 (2)°.

The molecules are linked into a two-dimensional network parallel to the (100) by N—H···N hydrogen bonds (Table 1 and Fig.3).

Related literature top

For a summary of structural data for 1,2,4-triazoles, see: Buzykin et al. (2006). For the crystal structure of 3-pyridin-2-yl-1,2,4-triazol-5-amine, see: Dolzhenko et al. (2009). For the use of 1,2,4-triazol-5-amines as building blocks in the synthesis of fused heterocyclic systems, see: Dolzhenko et al. (2006, 2007a,b); Fischer (2007).

Experimental top

(5)-Phenyl-1,2,4-triazol-5(3)-amine was prepared according to Dolzhenko et al. (2007a,b). The crystals suitable for crystallographic analysis were grown by recrystallization from ethanol.

Refinement top

N-bound H-atoms were located in a difference map and refined freely. C-bound H atoms were positioned geometrically (C-H = 0.94 Å) and were constrained in a riding motion approximation with Uiso(H) = 1.2Ueq(C).

Computing details top

Data collection: SMART (Bruker, 2001); cell refinement: SAINT (Bruker, 2001); data reduction: SAINT (Bruker, 2001); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXS97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. Possible tautomers of 3(5)-phenyl-1,2,4-triazol-5(3)-amine.
[Figure 2] Fig. 2. The molecular structure of 3(5)-phenyl-1,2,4-triazol-5(3)-amine with the atomic numbering scheme. Displacement ellipsoids are drawn at the 50% probability level.
[Figure 3] Fig. 3. Molecular packing in the crystal, viewed along the b axis. Hydrogen bonds are shown as dashed lines.
3-Phenyl-1H-1,2,4-triazol-5-amine–5-phenyl-1H-1,2,4-triazol- 3-amine (1/1) top
Crystal data top
C8H8N4·C8H8N4F(000) = 672
Mr = 320.36Dx = 1.387 Mg m−3
Monoclinic, P21/cMelting point: 460 K
Hall symbol: -P 2ybcMo Kα radiation, λ = 0.71073 Å
a = 17.817 (2) ÅCell parameters from 1028 reflections
b = 5.0398 (6) Åθ = 2.4–22.6°
c = 18.637 (2) ŵ = 0.09 mm−1
β = 113.573 (4)°T = 223 K
V = 1533.9 (3) Å3Rod, colourless
Z = 40.60 × 0.10 × 0.06 mm
Data collection top
Bruker SMART APEX CCD
diffractometer		3523 independent reflections
Radiation source: fine-focus sealed tube2394 reflections with I > 2σ(I)
graphiteRint = 0.063
φ and ω scansθmax = 27.5°, θmin = 2.2°
Absorption correction: multi-scan
(SADABS; Sheldrick, 2001)		h = −17→23
Tmin = 0.947, Tmax = 0.995k = −6→6
10288 measured reflectionsl = −24→20
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)] = 0.067Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.168H atoms treated by a mixture of independent and constrained refinement
S = 0.99 w = 1/[σ2(Fo2) + (0.0813P)2 + 0.5041P]
where P = (Fo2 + 2Fc2)/3
3523 reflections(Δ/σ)max = 0.001
241 parametersΔρmax = 0.43 e Å−3
0 restraintsΔρmin = −0.24 e Å−3
Crystal data top
C8H8N4·C8H8N4V = 1533.9 (3) Å3
Mr = 320.36Z = 4
Monoclinic, P21/cMo Kα radiation
a = 17.817 (2) ŵ = 0.09 mm−1
b = 5.0398 (6) ÅT = 223 K
c = 18.637 (2) Å0.60 × 0.10 × 0.06 mm
β = 113.573 (4)°
Data collection top
Bruker SMART APEX CCD
diffractometer		3523 independent reflections
Absorption correction: multi-scan
(SADABS; Sheldrick, 2001)		2394 reflections with I > 2σ(I)
Tmin = 0.947, Tmax = 0.995Rint = 0.063
10288 measured reflectionsθmax = 27.5°
Refinement top
R[F2 > 2σ(F2)] = 0.067H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.168Δρmax = 0.43 e Å−3
S = 0.99Δρmin = −0.24 e Å−3
3523 reflectionsAbsolute structure: ?
241 parametersFlack parameter: ?
0 restraintsRogers parameter: ?
Special details top

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 > 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*/Ueq
N10.45958 (12)0.2679 (4)0.41243 (11)0.0227 (5)
N20.44655 (12)0.1498 (4)0.29112 (11)0.0228 (5)
N30.50228 (12)0.3557 (4)0.31965 (12)0.0232 (5)
H3N0.5206 (17)0.441 (6)0.2883 (17)0.034 (8)*
N40.55437 (15)0.6210 (5)0.43462 (14)0.0306 (5)
H4A0.5543 (18)0.650 (6)0.483 (2)0.047 (9)*
H4B0.5900 (18)0.694 (6)0.4217 (17)0.038 (8)*
C10.36387 (14)−0.0976 (5)0.34673 (13)0.0221 (5)
C20.32601 (15)−0.2542 (5)0.28099 (14)0.0275 (6)
H20.3384−0.22970.23690.033*
C30.26999 (16)−0.4464 (5)0.27973 (16)0.0326 (6)
H30.2450−0.55250.23490.039*
C40.25056 (16)−0.4837 (5)0.34337 (16)0.0317 (6)
H40.2119−0.61280.34200.038*
C50.28814 (18)−0.3303 (6)0.40898 (17)0.0405 (7)
H50.2754−0.35570.45280.049*
C60.34456 (17)−0.1385 (6)0.41101 (16)0.0352 (7)
H60.3700−0.03520.45630.042*
C70.42378 (14)0.1068 (5)0.34941 (13)0.0205 (5)
C80.50768 (14)0.4241 (5)0.39146 (13)0.0223 (5)
N50.18197 (12)0.2602 (4)0.01779 (11)0.0225 (5)
N60.17613 (13)−0.1706 (4)0.02735 (12)0.0241 (5)
H6N0.165 (2)−0.339 (7)0.0188 (19)0.057 (10)*
N70.25003 (12)−0.1005 (4)0.08543 (11)0.0247 (5)
N80.31434 (13)0.3193 (5)0.12197 (13)0.0257 (5)
H8A0.3424 (19)0.261 (6)0.1652 (19)0.042 (9)*
H8B0.302 (2)0.500 (7)0.1168 (19)0.055 (10)*
C90.05728 (14)0.0322 (5)−0.07822 (14)0.0237 (5)
C100.03648 (17)0.2181 (5)−0.13815 (16)0.0341 (7)
H100.07410.3502−0.13710.041*
C11−0.04013 (18)0.2079 (6)−0.19945 (17)0.0444 (8)
H11−0.05420.3339−0.23990.053*
C12−0.09593 (17)0.0147 (6)−0.20168 (17)0.0423 (8)
H12−0.14770.0092−0.24350.051*
C13−0.07527 (17)−0.1708 (6)−0.14209 (18)0.0417 (8)
H13−0.1131−0.3025−0.14320.050*
C140.00090 (17)−0.1621 (6)−0.08100 (16)0.0345 (6)
H14A0.0148−0.2891−0.04080.041*
C150.13744 (15)0.0420 (5)−0.01207 (13)0.0219 (5)
C160.24976 (14)0.1614 (5)0.07732 (13)0.0198 (5)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
N10.0273 (11)0.0216 (10)0.0205 (10)−0.0031 (9)0.0108 (9)−0.0002 (8)
N20.0274 (11)0.0216 (10)0.0200 (10)−0.0022 (9)0.0099 (8)−0.0016 (8)
N30.0306 (11)0.0236 (11)0.0193 (10)−0.0060 (9)0.0143 (9)−0.0013 (9)
N40.0378 (13)0.0325 (13)0.0266 (12)−0.0140 (11)0.0182 (10)−0.0090 (10)
C10.0229 (12)0.0212 (12)0.0217 (12)0.0036 (10)0.0082 (10)−0.0010 (10)
C20.0293 (13)0.0302 (14)0.0244 (13)−0.0007 (11)0.0122 (11)−0.0013 (11)
C30.0286 (14)0.0343 (15)0.0310 (14)−0.0080 (12)0.0079 (11)−0.0104 (12)
C40.0268 (14)0.0275 (14)0.0419 (15)−0.0067 (11)0.0150 (12)0.0017 (12)
C50.0476 (18)0.0449 (17)0.0391 (16)−0.0131 (15)0.0279 (14)−0.0024 (14)
C60.0448 (16)0.0356 (15)0.0298 (14)−0.0133 (13)0.0197 (13)−0.0075 (12)
C70.0249 (12)0.0190 (12)0.0176 (11)0.0031 (10)0.0085 (9)0.0007 (9)
C80.0237 (12)0.0228 (13)0.0208 (12)0.0009 (10)0.0093 (10)0.0011 (10)
N50.0246 (10)0.0196 (10)0.0214 (10)0.0019 (8)0.0072 (8)−0.0015 (8)
N60.0264 (11)0.0176 (11)0.0250 (11)0.0004 (9)0.0067 (9)0.0018 (9)
N70.0276 (11)0.0219 (11)0.0211 (10)0.0015 (9)0.0061 (9)0.0004 (8)
N80.0267 (12)0.0222 (12)0.0223 (11)0.0028 (9)0.0037 (9)−0.0001 (9)
C90.0223 (12)0.0203 (12)0.0277 (13)0.0023 (10)0.0091 (10)−0.0052 (10)
C100.0383 (15)0.0234 (13)0.0338 (14)0.0007 (12)0.0073 (12)0.0002 (11)
C110.0453 (18)0.0347 (17)0.0357 (16)0.0085 (14)−0.0022 (14)0.0022 (13)
C120.0278 (15)0.0420 (18)0.0431 (17)0.0073 (13)−0.0008 (13)−0.0139 (14)
C130.0285 (15)0.0431 (17)0.0506 (18)−0.0101 (13)0.0126 (13)−0.0157 (15)
C140.0357 (15)0.0313 (15)0.0349 (15)−0.0016 (12)0.0123 (12)−0.0024 (12)
C150.0261 (12)0.0193 (12)0.0218 (12)0.0001 (10)0.0113 (10)−0.0022 (10)
C160.0241 (12)0.0196 (12)0.0166 (11)0.0031 (10)0.0092 (9)−0.0009 (9)
Geometric parameters (Å, °) top
N1—C81.332 (3)N5—C151.340 (3)
N1—C71.359 (3)N5—C161.366 (3)
N2—C71.321 (3)N6—C151.326 (3)
N2—N31.387 (3)N6—N71.375 (3)
N3—C81.348 (3)N6—H6N0.87 (4)
N3—H3N0.89 (3)N7—C161.328 (3)
N4—C81.337 (3)N8—C161.372 (3)
N4—H4A0.92 (3)N8—H8A0.81 (3)
N4—H4B0.85 (3)N8—H8B0.94 (4)
C1—C21.385 (3)C9—C141.389 (4)
C1—C61.388 (3)C9—C101.390 (4)
C1—C71.470 (3)C9—C151.468 (3)
C2—C31.385 (4)C10—C111.387 (4)
C2—H20.94C10—H100.94
C3—C41.375 (4)C11—C121.380 (4)
C3—H30.94C11—H110.94
C4—C51.373 (4)C12—C131.384 (4)
C4—H40.94C12—H120.94
C5—C61.384 (4)C13—C141.380 (4)
C5—H50.94C13—H130.94
C6—H60.94C14—H14A0.94
C8—N1—C7103.55 (19)C15—N5—C16102.86 (19)
C7—N2—N3102.47 (18)C15—N6—N7110.6 (2)
C8—N3—N2109.15 (19)C15—N6—H6N131 (2)
C8—N3—H3N129.2 (18)N7—N6—H6N118 (2)
N2—N3—H3N120.4 (18)C16—N7—N6101.93 (18)
C8—N4—H4A118 (2)C16—N8—H8A115 (2)
C8—N4—H4B121 (2)C16—N8—H8B113 (2)
H4A—N4—H4B120 (3)H8A—N8—H8B119 (3)
C2—C1—C6118.5 (2)C14—C9—C10119.3 (2)
C2—C1—C7121.3 (2)C14—C9—C15120.1 (2)
C6—C1—C7120.2 (2)C10—C9—C15120.7 (2)
C3—C2—C1120.4 (2)C11—C10—C9119.7 (3)
C3—C2—H2119.8C11—C10—H10120.2
C1—C2—H2119.8C9—C10—H10120.2
C4—C3—C2120.6 (2)C12—C11—C10120.7 (3)
C4—C3—H3119.7C12—C11—H11119.6
C2—C3—H3119.7C10—C11—H11119.6
C5—C4—C3119.3 (2)C11—C12—C13119.7 (3)
C5—C4—H4120.3C11—C12—H12120.2
C3—C4—H4120.3C13—C12—H12120.2
C4—C5—C6120.5 (3)C14—C13—C12119.9 (3)
C4—C5—H5119.7C14—C13—H13120.0
C6—C5—H5119.7C12—C13—H13120.0
C5—C6—C1120.5 (3)C13—C14—C9120.7 (3)
C5—C6—H6119.7C13—C14—H14A119.6
C1—C6—H6119.7C9—C14—H14A119.6
N2—C7—N1114.8 (2)N6—C15—N5110.0 (2)
N2—C7—C1123.0 (2)N6—C15—C9123.7 (2)
N1—C7—C1122.1 (2)N5—C15—C9126.3 (2)
N1—C8—N4125.5 (2)N7—C16—N5114.6 (2)
N1—C8—N3110.0 (2)N7—C16—N8122.9 (2)
N4—C8—N3124.6 (2)N5—C16—N8122.4 (2)
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
N3—H3N···N2i0.89 (3)2.08 (3)2.966 (3)175 (3)
N4—H4A···N1ii0.92 (3)2.09 (3)3.011 (3)173 (3)
N4—H4B···N8i0.85 (3)2.25 (3)3.091 (3)170 (3)
N6—H6N···N5iii0.87 (4)2.04 (4)2.879 (3)159 (3)
N8—H8A···N20.81 (3)2.41 (3)3.206 (3)168 (3)
N8—H8B···N7iv0.94 (4)2.19 (4)3.115 (3)169 (3)
Symmetry codes: (i) −x+1, y+1/2, −z+1/2; (ii) −x+1, −y+1, −z+1; (iii) x, y−1, z; (iv) x, y+1, z.
Table 1
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
N3—H3N···N2i0.89 (3)2.08 (3)2.966 (3)175 (3)
N4—H4A···N1ii0.92 (3)2.09 (3)3.011 (3)173 (3)
N4—H4B···N8i0.85 (3)2.25 (3)3.091 (3)170 (3)
N6—H6N···N5iii0.87 (4)2.04 (4)2.879 (3)159 (3)
N8—H8A···N20.81 (3)2.41 (3)3.206 (3)168 (3)
N8—H8B···N7iv0.94 (4)2.19 (4)3.115 (3)169 (3)
Symmetry codes: (i) −x+1, y+1/2, −z+1/2; (ii) −x+1, −y+1, −z+1; (iii) x, y−1, z; (iv) x, y+1, z.
Acknowledgements top

This work was supported by the National Medical Research Council, Singapore (grant Nos. NMRC/NIG/0019/2008 and NMRC/NIG/0020/2008).

references
References top

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