A first method for obtaining of electron-rich bioctahedral rhenium clusters has been developed. Two cluster salts, namely (Et3NH)4(Me2NH2)4[Re12CS14(µ-S)3Cl6] (1) and (Et4N)4(Me2NH2)4[Re12CS14(µ-S)3Br6] (2), have been synthesized and isolated in the solid state. Single-crystal X-ray diffraction showed that salts 1 and 2 are based on the new cluster anions [Re12CS14(µ-S)3Cl6]8− and [Re12CS14(µ-S)3Br6]8− containing 48 cluster valence electrons (CVE). The correlations between geometry and CVE number of the bioctahedral chalcohalide anions have been examined using the DFT calculations. The dissolution of the salts 1 and 2 is accompanied by the oxidation yielding the [Re12CS14(µ-S)3Cl6]6− and [Re12CS14(µ-S)3Br6]6− anions. Properties of the new clusters in the DMSO solutions have been investigated by UV–Vis spectroscopy and cyclic voltammetry. The latter revealed the presence of multiple reversible one-electron redox waves in a narrow potential window.