Acta Cryst. (2004). E60, o1285-o1287 [ doi:10.1107/S1600536804015521 ]
Abstract: In the title compound, bis[3,7-bis(cyclopropylmethyl)-7-aza-3-azoniaspiro[bicyclo[3.3.1]nonane-9,1'-cyclopentane]] (2E)-but-2-enedionate bis[(2E)-but-2-enedioic acid], 2C19H33N2+·C4H2O42-·2C4H4O4, the cations are protonated at only one N atom and there is no evidence of any disorder involving the alternative nitrogen. The system N+-HN represents an intramolecular hydrogen bond. The fumarate and fumaric acid residues form a network of 50-membered rings by classical hydrogen bonding; the cations are linked to these by C-HO contacts.
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