Therefore, we believe that understanding the nature of the metal-metal bonding in the transition metal corrole dimers is still in need of further investigation using computational methods that are beyond the single determinant method (DFT). Here we report a computational study on the {M[TpMePC]}2 (M = Re or Os) complexes and their oxidation and reduction forms to shed some light on the nature of the metal-metal bonding in these important complexes using the complete active space self-consistent field (CASSCF) methodology.