Crystal structure of zwitterionic 3,3'-[1,1'-(butane-1,4-di-yl)bis-(1-imidazol-3-ium-3,1-di-yl)]bis-(propane-1-sulfonate) dihydrate.

The crystal structure of the title compound, CHNOS·2HO, a water-soluble di--heterocyclic carbene ligand precursor was determined using a single crystal grown by the slow cooling of a hot ,-di-methyl-formamide solution of the compound. The dihydrate crystallizes in the monoclinic space group 2/, with half of the zwitterionic mol-ecule and one water mol-ecule of crystallization in the asymmetric unit. The remaining part of the mol-ecule is completed by inversion symmetry.