RESUMO

Extended Hückel 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 M(8) cube in a way similar to the dithiolato ligands in the Cu(8) species.