Acta Cryst. (2012). E68, o3321-o3322
[ doi:10.1107/S1600536812045308 ]
Abstract: In the title salt, 2C4H6ClN4+·C4H2O42-, the complete fumarate dianion is generated by crystallographic inversion symmetry. The cation is essentially planar, with a maximum deviation of 0.018 (1) Å. In the anion, the carboxylate group is twisted slightly away from the attached plane, the dihedral angle between the carboxylate and (E)-but-2-ene planes being 12.78 (13)°. In the crystal, the protonated N atom and the 2-amino group of the cation are hydrogen bonded to the carboxylate O atoms of the anion via a pair of N-HO hydrogen bonds, forming an R22(8) ring motif. In addition, another type of R22(8) motif is formed by centrosymmetrically related pyrimidinium cations via N-HN hydrogen bonds. These two combined motifs form a heterotetramer. The crystal structure is further stabilized by stong N-HO, N-HCl and weak C-HO hydrogen bonds, resulting a three-dimensional network.
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