Amino(5-{2-[amino(iminio)methyl]hydrazin-1-yl}-3,5-dimethyl-4,5-dihydro-1H-pyrazol-1-yl)methaniminium dinitrate

The reaction of aqueous solutions of aminoguanidine hydrogennitrate and acetylacetone produces the title pyrazole salt, C7H18N8 2+·2NO3 −. The crystal structure is stabilized by a complex N—H⋯O hydrogen-bonding network. The difference in the engagement of the two nitrate anions in hydrogen bonding is reflected in the variation of the corresponding N—O bond lengths.

The reaction of aqueous solutions of aminoguanidine hydrogennitrate and acetylacetone produces the title pyrazole salt, C 7 H 18 N 8 2+ Á2NO 3 À . The crystal structure is stabilized by a complex N-HÁ Á ÁO hydrogen-bonding network. The difference in the engagement of the two nitrate anions in hydrogen bonding is reflected in the variation of the corresponding N-O bond lengths.

Comment
In the paper (Thiele & Dralle, 1898) the reaction of aqueous aminoguanidine hydrogennitrate and acetylacetone solutions was described which, according to the authors, led to the formation of acetylacetonebis(aminoguanidine) dihydrogendinitrate (C 7 H 16 N 8 .2HNO 3 ). However, our investigations of the crystal and molecular structure of the obtained product have shown that this reaction did not form the cited Schiff base but a cyclic product of the same chemical composition, i.e.

Experimental
To a solution of aminoguanidine hydrogennitrate (1.4 g, 10 mmol) in H 2 O (20 ml) acetylacetone (0.5 ml, 5 mmol) was added. The reaction mixture was homogenized by stirring on magnetic stirrer (20 min) at room temperature. After three days the resulting white crystals have been filtered and washed with water (35% yield).

Refinement
The H atoms bonded to C and N atoms were placed at geometrically calculated positions and refined using a riding model.
C-H distances were fixed to 0.96 and 0.97 Å from methyl and methylene C atoms respectively. Their U iso (H) values where supplementary materials sup-2 equal to 1.5 times U eq of the corresponding C (sp 3 ) atom. N-H distances were fixed to 0.86 Å with U iso (H) values equal to 1.2 U eq of the parent N.
In the absence of significant anomalous scattering, the absolute configuration could not be reliably determined and then the Friedel pairs were merged and any references to the Flack parameter were removed. Fig. 1. The molecular structure of (I), with atom labels and 50% probability displacement ellipsoids for non-H atoms. H atoms are represented as small spheres of arbitrary radii. Hydrogen bonds are shown as dashed lines.

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.