Spin unrestricted DFT geometry optimization was performed on 1 -4 assuming singlet, triplet, and septet spin states. Singlet and septet configurations have similar energies for 1 and 2, achieved in both cases by high-spin Co centers with opposite (singlet) or equivalent (septet) spin densities (Table ). The singlet state is most stable for 3 and 4, with no spin density on either Co site. Broken symmetry calculations for 3 and 4 also converged to a closed-shell ground state, with no spin density on Co. These results are consistent with the 1 H NMR Evans method measurements. Similar behavior has been observed in dirhodium(II) species which are closed shell binuclear complexes, despite having odd number of electrons on the Rh centers. The DFToptimized bond lengths for all compounds agree well with those measured by X-ray crystallography and Co K-edge EXAFS (Tables ), confirming the structural validity of the DFT model.