Selective substitution of mu-SO22- groups by either O2- or Se2- ions occurs upon heating the bioctahedral rhenium cluster complex K-6[Re12CS14(mu-SO2)(3)(CN)(6)] in air atmosphere or in the presence of a Se source, respectively, manifesting the remarkable lability of SO22- ligands bound to a transition-metal cluster. A series of compounds based on the new mixed-ligand anions, [Re12CS14(mu-O)(3)(CN)(6)](6-), [Re12CS14(mu-Se)(3)(CN)(6)](6-), and [Re12CS14(mu-O)(3)(OH)(6)](6-), were isolated and their solid-state structures were elucidated by single-crystal X-ray diffraction analysis. Along with the previously reported mu-sulfide clusters, the new species constitute a series of rhenium anionic complexes with the common formula [Re12CS14(mu-Q)(3)L-6](5-) (Q = O, S, Se, L = CN-; Q = O, S, L = OH-), within which the total charge and number of cluster valence electrons (CVEs) are constant. The article presents insights into the mechanistic and synthetic aspects of the subStitution process, and it comprehensively discusses the influence of inner ligand environment on the structure, spectroscopic characteristics, and electrochemical behavior of the novel compounds.