Redetermination of the salt hexa­methyl­ene­tetra­minium fumarate

The crystal structure of the title compound [systematic name: 3,5,7-triaza-1-azoniatricyclo­[3.3.1.1(3,7)]decane (E)-3-carb­oxy­prop-2-enoate], C(6)H(13)N(4) (+)·C(4)H(3)O(4) (−), had been determined previously by Bowes et al. [Acta Cryst. (2003), B59, 100–117]. Their structure contained an approximately 3:1 ratio of fumarate and succinate monoanions disordered over the same position. The succinate anion component forms a similar structural role to the fumarate anion and came about due to an impurity in the starting material, fumaric acid. In this work, the crystal structure of the pure salt is presented, which is identical, apart from the lack of disorder of the anions, to the previous structure. In the crystal, the ions assemble in the solid state, forming chains via N(+)—H⋯O(−) and O—H⋯O(−) hydrogen bonds, which are linked into a three-dimensional network by C—H⋯O inter­actions.