Abstract
In the cation of the title salt, C11H17N2O(+)·C7H8ClN2O2 (-), the piperazine ring adopts a distorted chair conformation and contains a positively charged N atom with quaternary character. Its mean plane makes a dihedral angle of 42.36 (8)° with the phenyl ring of its 2-meth-oxy-phenyl substituent. The 2,4-dioxopyrimidin-1-ide anion is generated by deprotonation of the N atom at the 1-position of the pyrimidine-dione ring. Intra-molecular C-H⋯O hydrogen bonds generate S(6) ring motifs in both the cation and the anion. In the crystal, N-H⋯O, N-H⋯N and C-H⋯O hydrogen bonds are also observed, resulting in a two-dimensional network parallel to the ab plane. The crystal stability is further consolidated by weak C-H⋯π inter-actions.