2-Amino-5-chloropyridinium hydrogen succinate

In the title salt, C5H6ClN2 +·C4H5O4 −, the pyridine N atom is protonated. The pyridinium and amino groups associate via a pair of N—H⋯O hydrogen bonds to the carboxylate O atoms of the singly deprotonated succinate anion. The hydrogen succinate anions self-assemble via O—H⋯O hydrogen bonds into chains along the b axis. The crystal structure is further stabilized by additional N—H⋯O hydrogen bonds involving the second amino H atoms, as well as C—H⋯O contacts, forming a three-dimensional network.

In the title salt, C 5 H 6 ClN 2 + ÁC 4 H 5 O 4 À , the pyridine N atom is protonated. The pyridinium and amino groups associate via a pair of N-HÁ Á ÁO hydrogen bonds to the carboxylate O atoms of the singly deprotonated succinate anion. The hydrogen succinate anions self-assemble via O-HÁ Á ÁO hydrogen bonds into chains along the b axis. The crystal structure is further stabilized by additional N-HÁ Á ÁO hydrogen bonds involving the second amino H atoms, as well as C-HÁ Á ÁO contacts, forming a three-dimensional network.
In the crystal packing (Fig. 2), the protonated N1 atom and the 2-amino group is hydrogen-bonded to the carboxylate oxygen atoms (O1 and O2) via a pair of N-H···O hydrogen bonds forming a R 2 2 (8) ring motif (Bernstein et al. 1995

Experimental
A hot methanolic solution (10 ml) of 2-amino-5-chloropyridine (32 mg, Aldrich) and a hot aqueous solution (10 ml) of succinic acid (29 mg, Merck) were mixed and warmed over a water bath for 10 minutes. The resulting solution was allowed to cool slowly at room temperature. Single crystals of (I) appeared from the mother liquor after a few days.

Refinement
All the H atoms were located in a difference Fourier map and allowed to refine freely [N-H = 0.83 (2) Fig. 1. The asymmetric unit of (I) showing atom labelling scheme. Displacement ellipsoids are drawn at the 50% probability level.

Special details
Experimental. The crystal was placed in the cold stream of an Oxford Cryosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) k.
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 > 2sigma(F 2 ) is used only for calculating R-factors(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.