Crystal structures of morpholinium hydrogen bromanilate at 130, 145 and 180K

Crystal structures of the title compound (systematic name: morpholin-4-ium 2,5-dibromo-4-hydroxy-3,6-dioxocyclohexa-1,4-dien-1-olate), C₄H₁₀NO⁺·C₆HBr₂O₄ ^-, were determined at three temperatures, viz. 130, 145 and 180K. The asymmetric unit comprises one morpholinium cation and two halves of crystallographically independent bromanilate monoanions, which are located on inversion centres. The conformations of the two independent bromanilate anions are different from each other with respect to the O - H orientation. In the crystal, the two different anions are linked alternately into a chain along [211] through a short O - H⋯O hydrogen bond, in which the H atom is disordered over two positions. The refined site-occupancy ratios, which are almost constant in the temperature range studied, are 0.49(3):0.51(3), 0.52(3):0.48(3) and 0.50(3):0.50(3), respectively, at 130, 145 and 180K, and no significant difference in the molecular geometry and the molecular packing is observed at the three temperatures. The morpholinium cation links adjacent chains of anions via N - H⋯O hydrogen bonds, forming a sheet structure parallel to (-111).