A monoclinic polymorph of N-ethoxycarbonyl-N′-(3-phenyl-1H-1,2,4-triazol-5-yl)thiourea

The title compound, C12H13N5O2S {systematic name: ethyl N-[N-(3-phenyl-1H-1,2,4-triazol-5-yl)carbamothioyl]carbamate}, is a monoclinic polymorph (space group P21/c) which crystallizes with three similar independent molecules in the asymmetric unit. The triazole ring makes dihedral angles of 6.6 (2), 8.4 (2) and 10.6 (2)° with the phenyl ring in the three independent molecules. The structure was previously reported [Dolzhenko et al. (2010a ▶). Acta Cryst., E46, o425] as a triclinic polymorph crystallizing in space group P . Molecules in both polymorphs possess two S(6) rings generated by intramolecular N—H⋯S and N—H⋯O hydrogen bonds, resulting in similar molecular geometries. However, the two polymorphs differ in the crystal packing. In contrast to the dimers of the triclinic polymorph, molecules of the monoclinic polymorph are connected by intermolecular N—H⋯S and N—H⋯N hydrogen bonds, forming pseudosymmetric trimers arranged in sheets parallel to (302).

In both polymorph, the N-H···S hydrogen bonds between the endocyclic NH group of the triazole ring and the thioureido sulfur atom ( Fig. 2 and Table 1) are arranged in a S6 graph-set motif (Bernstein et al., 1995) stabilizing the tautomer structure.
The general configurations of the carbethoxythiourea group in the title molecule replicate that of previously reported for triclinic polymorph (Dolzhenko et al., 2010a) and a similar structure (Dolzhenko et al., 2010b). The strong intramolecular hydrogen bonding between carbonyl oxygen atom and thiourea NH group arranged in S(6) graph-set motif which is common for carbethoxythioureas (Dolzhenko et al., 2010a,b). In the three independent molecules, the triazole ring make dihedral angles of 6.6 (2)°, 8.4 (2)° and 10.6 (2)° with the corresponding phenyl rings [cf. 6.59 (10)° for the triclinic polymorph (Dolzhenko et al., 2010a)].
The monoclinic and triclinic polymorphs are significantly different in crystal packing. In contrast to the dimers of triclinic polymorph (Dolzhenko et al., 2010a), molecules of monoclinic polymorph are connected with intermolecular hydrogen bonding of the C═S···H-N-N···H-N pattern forming pseudosymmetric trimer structures arranged in sheets parallel to the (302) plane.

Refinement
All the H atoms attached to the carbon atoms were constrained in a riding motion approximation [0.94 Å for C aryl -H, 0.98 Å for methylene H atoms and 0.97 Å for methyl groups; U iso (H) = 1.2U eq (C aryl and C methylene ) and 1.5U eq (C methyl )] while the N-bound H atoms were located in a difference map and refined with restraints in bond length and thermal parameters.
One of the ethoxy -OCH 2 CH 3 group is disordered over two orientations with occupancies of 0.634 (7) and 0.366 (7). The corresponding bond distances in the disorder components were restrained to be the same. The U ij parameters of disordered atoms were restrained to an approximate isotropic behaviour.   -carbethoxy-N'-(3-phenyl-1H-1,2,4-triazol-5-yl)