Extended Huckel and density functional calculations carried out on 128-MVE Cu-8(dithiolato)(6) edge-bridged cubic clusters indicate that their stability is mainly driven by the chelating effect of the ligands, which provide a stable 16-electron configuration to the approximately trigonal planar metal centers. Nevertheless, a weak but significant d(10)-d(10) bonding interaction is present which is rather independent from the dithiolato bite effect. The metal centers have a nonbonding 4p(z) vacant AO pointing to the center of the cube available for bonding to an encapsulated atom. The electronic closed-shell requirement is satisfied for the 136-MVE and 140-MVE counts, respectively, when a main-group atom or a transition-metal atom is incorporated in the middle of the cube. The bonding within these dithiolato compounds is compared to other edge-bridged M-8 cubic clusters. In particular, it is shown that clusters of higher nuclearity but containing an M-8 cubic core are related to the dithiolato species. Indeed, their outer metal atoms can be considered as belonging to the ligand shell, interacting with the Mg cube in a way similar to the dithiolato ligands in the Cu-8 species.