Crystal structures of an isomeric pair of 3-methylthio-5-amino-1,2,4-triazoles (original) (raw)

1984, Journal of Molecular Structure

The structures of an isomeric pair: l-[2-(2,6-dichlorophenoxy)-ethyl]-3-methylthio-5-amino-m-1,2,4-triazole (IV) and 2-[ 2-( 2,6-dichlorophenoxy)-ethyl] -3-methylthio-5-amino=-1,2,4-triazole (V) have been established by X-ray crystallography from diffractometer data. Crystals of IV are monoclinic, space group P2,/c with a = 11.220(l), b = 10.005(3), c = 12.784(3) A, p = 91.99(l)', 2 = 4, D, = 1.478 g cm-'. CrystalsofV are orthorhombic, space group Pbca with a = 'i-618(2), b = 14.289(4), c = 26.494(7) A, Z = 8, D, = 1.470 g cm-. The structures determined by direct methods were refined to R = 0.060 for 1931 reflections of IV and R = 0.061 for 1315 reflections of V. The X-ray analysis corroborated the structures assigned to the isomeric pair on the basis of proton coupled 13C-NMR spectra The features (i.e. the sequence of the endocyclic bond angle magnitudes) of the planar s-triazole rings are governed by the same rules reported recently by Kalman and Argay [J. Mol. Struct., 102 (1983) 3911 discussing the structures of the related I, II and III compounds. In contrast to I, II, III and IV the S(6 j C(7) bond of V is almost perpendicular to the best plane of the s-triazole ring C(7)-S(6)-C(3)-N(4) = -79.0(7)". This unusual orientation of the S-methyl bond is created by the steric hindrance of the very same uicinal P-ethyl (C(S)H,-C(lO)H,)