REVERSIBLE TOPOTACTIC HYDRATION AND DEHYDRATION OF AN EUROPIUM COMPLEX

Solid samples of the salt [Eu[L-OEt](2)(H2O)(2)]BF4, ((L-OEt) = [CoCp{ P(OEt)(2)O}(3)]) may be reversibly dehydrated under very mild conditio ns to give the corresponding mono aqua complex [Eu(L-OEt)(2)(H2O)]BF4. The conversion can be monitored by single crystal x-ray diffraction, In the course of the reaction the crystallinity of the substance is re tained: both compounds crystallize in space group P2(1)/c with similar lattice constants and essentially the same packing arrangement. The c ations show the expected change in the Eu coordination geometry with l onger metal-ligand distances for the higher coordinated Eu atoms in th e diaqua complex. The crystalline-stale reaction is facilitated by a s uitable morphology.