Received 22 October 2012
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.
For applications of pyrimidine derivatives, see: Condon et al. (1993); Maeno et al. (1990); Gilchrist (1997). For details of fumaric acid, see: Batchelor et al. (2000). For hydrogen-bonded synthons, see: Thakur & Desiraju (2008). For hydrogen-bond motifs, see: Bernstein et al. (1995). For bond-length data, see: Allen et al. (1987). For stability of the temperature controller used for the data collection, see: Cosier & Glazer (1986).
Data collection: APEX2 (Bruker, 2009); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009).
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: RZ5019 ).
The authors thank the Malaysian Government and Universiti Sains Malaysia (USM) for the research facilities and Fundamental Research Grant Scheme (FRGS) No. 203/PFIZIK/6711171 to conduct this work. KT thanks The Academy of Sciences for the Developing World and USM for a TWAS-USM fellowship.
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