title: The 2:1 complex of maleic acid and 1,4-diazabicyclo[2.2.2]octane: hydrogen-bonded sheets linked by C-H...O hydrogen bonds.
abstract: In the title complex, 1,4-diazoniabicyclo[2.2.2]octane bis(hydrogen maleate), C(6)H(14)N(2)(2+).2C(4)H(3)O(4)(-), the C(4)H(3)O(4)(-) and C(6)H(14)N(2)(2+) ions, derived from maleic acid and 1,4-diazabicyclo[2.2.2]octane, respectively, are disordered across a mirror plane in space group Cmc2(1), and they are linked by two nearly linear N-H...O hydrogen bonds, with N...O distances of 2.662 (3) and 2.614 (4) A, and N-H...O angles of 173 degrees. The crystal structure consists of sheets with reticulations of 3.3792 (4) A in stratum and 7.3892 (8) A in width. The sheets are linked by C-H...O hydrogen bonds.