2. Experimental

The title compound, C2H3N3OS, is a monoclinic (P21/c) polymorph of the previously reported triclinic structure [Kang et al. (2012). Acta Cryst. E68, o1198]. The asymmetric unit contains two independent molecules which are essentially planar, with r.m.s. deviations of 0.001 and 0.032 A ̊ from the mean plane defined by the seven non-H atoms. In the crystal, N—H N and N—H O hydrogen bonds link the molecules into a sheet parallel to (111)