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 K5[Re5WSe8(CN)6] and the chain polymer K6[Re3.6W2.4Se8(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)6]4–, [Re4W2Se8(CN)6]4–, and [Re3W3Se8(CN)6]4– 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.