The reaction of alkali metal hexacyanoferrate(II/III) with (CH,_)rN~ (hexamethylenetetramine, abbreviated HMT) in an acidic medium yielded crystalline compounds of stoichiometries HK2[Fem(CN)r] 9 2HMT 9 4H20, H2K.,[Feu(CN)6] 9 2HMT 9 4H,_O, and HNa2[Fem(CN)6] 9 2HMT 9 5H20. Their crystal structures are based on a packing of three molecular components: neutral and/or protonated HMT, hexacyanoferrate, and an alkali metal ion-water cluster. The resulting three-dimensional supramolecular framework is constructed from the coordination of the alkali metal ion by aqua ligands as well as [Fe(CN)6]"-and HMT units, and further stabilization is achieved by hydrogen bonding between water molecules and the noncoordinated nitrogen atoms of HMT and hexacyanoferrate.