2-(4-Chlorobenzoyl)-1-(diaminomethylene)hydrazinium chloride monohydrate

In the cation of the title compound, C8H10ClN4O+·Cl−·H2O, the guanidinium group is planar (maximum deviation = 0.0001 Å) and nearly perpendicular to carboxamide group, making a dihedral angle of 87.0 (3)°. The N atoms of the guanidine fragment have a planar trigonal configuration and the N atom of the carboxamide group adopts a pyramidal configuration. In the crystal structure, intermolecular N—H⋯O, N—H⋯Cl and O—H⋯Cl hydrogen bonds link the cations, anions and water molecules into layers parallel to the bc plane.

In the cation of the title compound, C 8 H 10 ClN 4 O + ÁCl À ÁH 2 O, the guanidinium group is planar (maximum deviation = 0.0001 Å ) and nearly perpendicular to carboxamide group, making a dihedral angle of 87.0 (3) . The N atoms of the guanidine fragment have a planar trigonal configuration and the N atom of the carboxamide group adopts a pyramidal configuration. In the crystal structure, intermolecular N-HÁ Á ÁO, N-HÁ Á ÁCl and O-HÁ Á ÁCl hydrogen bonds link the cations, anions and water molecules into layers parallel to the bc plane.
Carboxylic acids guanyl hydrazides can be regarded as acylated aminoguanidines. Therefore, by analogy with protonated aminoguanidine, it is possible to assume the existence of tautomeric forms A-C ( Fig. 1) for the title compound. In addition, the presence of acyl group makes it possible of tautomers D-G, the B-G forms can exist as cis-and trans-isomers.
Quantum chemical calculations predict the tautomer A is to be the more stable for aminoguanidine (Bharatam et al., 2004).
Thereby, the C 8 H 10 ClN 4 O cations, water molecules and chloride anions form a rigid three-dimensional framework in the crystal.

Special details
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 F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.