Abstract
The asymmetric unit of the title compound, 2C(10)H(18)N(+)center dot HPO42-center dot 1.5C(4)H(4)O(4), contains two adamantan-1-aminium cations, one hydrogen phosphate anion, and one and a half molecules of fumaric acid, one of which exhibits crystallographic inversion symmetry. Each HPO42- anion is hydrogen bonded, via all of its O atoms, to four NH3+ groups of the adamantan-1-aminium cations, forming chains along [100]. These chains are, in turn, interconnected via a set of O-H center dot center dot center dot O hydrogen bonds involving the fumaric acid solvent molecules, forming layers parallel to (001). Weak C-H center dot center dot center dot O interactions lead to a consolidation of the three-dimensional set-up.