Synthesis and Characterization of New Rare‐Earth Sandwich‐Type Tungstoarsenates

Two new sandwich‐type tungstoarsenate complexes [{Ln3O3(OH2)2}(AsW9O34)2]15− (Ln=La, Ce) were synthesized and studied using spectroscopy and cyclic voltammetry. Ion‐exchange experiments provided evidence for covalent, inner‐sphere bonding of the rare‐earth cations to the trilacunary [AsW9O34]9− polyoxometalate. Cyclic voltammograms of [{Ln3O3(OH2)2}(AsW9O34)2]15− exhibited two pairs of waves with negative potential values, which were attributed to the WVI/WV redox processes in the polyoxotungstate framework. Redox studies of the cerium derivative revealed the presence of two types of cerium ions.