Non-isovalent Substitution in High-Valence Metal Cluster Complexes: Synthesis and Study of Re–W Heterometallic Clusters

A previously unexplored reaction of ReSe2 and WSe2 in a KCN melt resulted in the formation of the heterometallic cluster products, namely, the salt K5Re5WSe8(CN)6 and the chain polymer K6Re3.6W2.4Se8(CN)4(CN)2/2. Oxidative depolymerization and the differences in redox behavior of the complexes enabled the isolation of soluble salts of the cluster anions Re5WSe8(CN)64–, Re4W2Se8(CN)64–, and Re3W3Se8(CN)64– with TBA+ cations as individual crystalline compounds. A comparative study of the complexes shows that sequential substitution of rhenium atoms in the cluster core with electron-deficient tungsten atoms leads to periodic variations in the physicochemical properties of the clusters. This is reflected, for instance, in a cathodic shift of the redox potentials and in the greater number of accessible charge states. At the same time, DFT calculations indicate that the octahedral cluster geometry for electron-precise complexes is almost insensitive to the number of tungsten atoms and undergoes local distortions upon variation of the cluster skeletal electron count.