Dynamic Uptake and Release of Water in the Mixed-Metal EDTA Complex M3[Yb(EDTA)(CO3)] (M = K, Rb, Cs)

Abstract

Ethylenediaminetetraacetic acid (H4EDTA) acts as a multidentate ligand toward ytterbium nitrate in the presence of M2CO3 (M = K, Rb, Cs). All structurally characterized compounds are three-dimensional coordination polymers with eight-coordinated ytterbium and three alkali metal cations in the asymmetric unit. In the presence of potassium cations, two different phase pure reaction products can be obtained. From a water-containing solution, first a water-deficient compound with composition K3[Yb(EDTA) (CO3)](H2O)·H2O precipitates. When kept in the reaction mixture, this kinetic product transforms into the more water-rich mixed-metal coordination network K3[Yb(EDTA)(CO3)](H2O)4·2H2O; alternatively, the conversion can be achieved by isolating the water-deficient product and immersing it into a water-containing solvent. The reverse reaction, partial dehydration, may be induced by prolonged drying in a desiccator, vacuum treatment, or heating. For the heavier alkali cations Rb+ and Cs+, only one crystalline str...