Conserved hydrogen-bonded supramolecular synthons in pyridinium tetrachlorometallates

The crystal and molecular structures of the pyridinium tetrahalometallates, [Hpy]2[CoCl4] and [Etpy]2[CoCl4], have been determined and compared with those of other pyridinium tetrahalometallates and 4,4'-bipyridinium perhalometallates. The pyridinium cation in [Hpy]2[CoCl4] uses its heterocyclic N–H and 4-positioned C–H moieties to form bifurcated hydrogen-bonds to tetrahalometallate anions and thus generate organic–inorganic hybrid solids similar in composition to those formed by 4,4-bipyridinium perhalometallate salts. Although the supramolecular synthons based on C–H donors are longer, and by inference, less strong, than those based on N–H donors, they are nonetheless, structure determining. The hydrogen-bonding capability of the ethylpyridinium cation is restricted to C–H donors and hence is not structure determining, the layered hexagonal network structure of [Etpy]2[CoCl4] being dominated by π–π stacking interactions