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 pi-pi stacking interactions.