Reversible solid-state reaction between 18-Crown[6] and M[H2PO4] (M = K, Rb, Cs) and an investigation of the decomplexation process

On heating the hydrated complexes 18-Crown[6].M[H2PO4].xH(2)O (x = 2 for M = K, Rb; x = 1.5 for M = Cs), quantitatively prepared by mechanical mixing of crystalline 18-Crown[6] and M[H2PO4], to ca. 60 degrees C, water loss takes place, accompanied by the extrusion of the crown ether from the crystalline complex and followed by reconstruction of the inorganic phase M[H2PO4] (M = K, Rb, Cs); the resulting solid mixture reverts to 18-Crown[6].M[H2PO4].xH(2)O (x = 2 for M = K, Rb; x = 1.5 for M = Cs) upon grinding in air.