Tailoring Heterometallic Cluster Functional Building Blocks: Synthesis, Separation, Structural and DFT Studies of [Re<sub>6−x</sub>Mo<sub>x</sub>Se<sub>8</sub>(CN)<sub>6</sub>]<sup>n−</sup>.
Influence of the metal core composition and geometry on the structure, spectroscopic properties and redox potentials was investigated for the first time for heterometallic (Re/Mo)6 octahedral clusters. The discrete anionic clusters [Re6‐xMoxSe8(CN)6]n− (x=2, 3; n=4, 5) were obtained as individual salts. Their isomeric composition and bond‐length distribution were inspected using a combination of single‐crystal X‐ray structure analysis, NMR, EXAFS, and DFT calculations.