Using XPS and DFT, we have studied a series of octahedral rhenium cluster compounds: ternary thiobromides Re₆S_4+nBr_10–2n, n = 0, 1, 3, 4 and alkali metal salts of anionic complexes [Re₆S_4+nBr_10-n]^n–, n = 1–4. These two series contain [Re₆S_4+nBr_4-n] cluster cores, which are the building blocks of both discrete complexes and polymeric compounds, and have the same coordination polyhedron of rhenium atoms. The constancy of the coordination polyhedron of Re reduces the effect of structural differences and allows to study the change in the electronic state of the rhenium atoms of the Re₆ metallocluster with increasing number of less electronegative (compared to bromine) sulfur atoms in the cluster core. This change results in the decrease in the binding energy (BE) Re 4f_7/2 in the series of anionic complexes [Re₆S_4+nBr_10-n]^n–. A similar dependence is observed in the series of ternary thiobromides. Re₆S₈Br₂ falls out of this trend, which is explained by a change in the type of binding of the cluster cores. The BE S 2p_3/2 of the sulfide ligands and the BE Br 3d_5/2 of the bromide ligands decrease as the number of sulfur atoms in the cluster core and the charge of anionic complexes increases. The difference in BE values for the inner Brⁱ and apical Br^a bromide ligands shows that the inner ligands are more covalent and the apical ligands are more ionic. Calculated energies of the Re 4f, S 2p, Br 3d orbitals confirm the general tendency for the energy to decrease as the number of sulfur atoms in the cluster cores increases. Calculation of the atom charges for discrete complexes [Re₆S_4+nBr_10-n]^n–, showed that with increasing number of sulfur atoms in the cluster cores, the negative charge of the ligands increases, while the charge of the rhenium atoms remains unchanged. This suggests that the chemical shift of the Re4f binding energy is determined by the potentials of the surrounding atoms (Madelung potential) and that the chemical shift of the ligands depends on the charge of the atom.