X-ray structural data for the cubane-type clusters [Mo₃CuS₄(dmpe)₃Cl₄]⁺ and Mo₃NiS₄(dmpe)₃Cl₄ (dmpe = 1,2-bis(dimethylphosphino)ethane) with 16 metal electrons have been compared with optimized structural parameters calculated using “ab initio” methodologies. Compound Mo₃NiS₄(dmpe)₃Cl₄ crystallizes in the cubic noncentrosymmetric space group P2₁3 with a Mo-Ni distance of 2.647 Å, that is 0.2 Å shorter than the Mo-Cu bond length in the isoelectronic copper cluster. The best agreement between theory and experiments has been obtained using the B3P86 method. In order to validate the B3P86 results, accurate infrared and Raman spectra have been acquired and the vibrational modes associated to the cubane-type Mo₃M’S₄ (M’ = Cu or Ni) unit have been assigned theoretically. The electronic changes taking place when incorporating the M’ into the Mo₃S₄ unit have been analyzed from a theoretical and experimental perspective. The bond dissociation energies between M’-Cl and Mo₃S₄ fragments show that formation of [Mo₃CuS₄(dmpe)₃Cl₄]⁺ is 135 kcal/mol energetically less favorable than the Ni incorporation. The more robust nature of the Mo₃NiS₄ fragment has been confirmed by mass spectrometry. The X-ray photoelectron spectroscopy (XPS) spectra of the trimetallic and tetrametallic complexes have been measured and the obtained binding energies compared with the computed electronic populations based on topological approaches of the electron localization function (ELF). The energies and shapes of the Cu 2p and Ni 2p lines indicate formal oxidation states of Cu(I) and Ni(II). However, the reductive addition of nickel into [Mo₃S₄(dmpe)₃Cl₃]⁺ causes a small decrease in the Mo 3d binding energies. This fact prevents an unambiguous assignment of an oxidation state in a conventional way, a circumstance that has been analyzed through the covariance of the electronic populations associated to the C(M’) core and V(Mo3Ni) and V(S(2)’) valence basins where Mo₃NiS₄ is a particularly electronically delocalized chemical entity.