Similarly, in the M' 2 Ni type nodes, M' is trivalent and Ni is divalent, maintaining charge neutrality. Given that the ligands carry a charge of -8, the total charge on the metals must be +8, as observed experimentally. The different possible spin-states for all the cases are listed in Table . The lowest-energy spin state at the M06-L level of theory was selected for subsequent comparisons of the reaction-energy barriers. A more detailed discussion of the spin-states is provided in Section S1 of the Supplementary Information.