In the crystal structure of the title compound, C(7)H(6)N(2)S, mol-ecules related by an inversion center are linked via N-H⋯N hydrogen bonds involving the amino groups, forming dimers. In turn, these dimers are linked via a second N-H⋯N hydrogen bond, forming an infinite two-dimensional network parallel to (011).

The asymmetric unit of the title compound, C6H9N3, contains three crystallographically independent mol-ecules of similar geometry. All of the mol-ecules are almost planar, with r.m.s. deviations of 0.003, 0.016 and 0.005 Å. In the crystal, the mol-ecules are linked by N-H⋯N hydrogen bonds into zigzag ribbons parallel to the c axis, generating rings of R2(2)(8) graph-set motif.

In the title compound, C(5)H(5)ClN(2), a by-product in the synthesis of ethyl 2-(3-chloro-pyridin-2-yl)-5-oxopyrazolidine-3-carboxyl-ate, the amine groups form inter-molecular hydrogen-bonding associations with pyridine N-atom acceptors, giving centrosymmetric cyclic dimers. Short inter-molecular Cl⋯Cl inter-actions [3.278 (3) Å] also occur.