In our free energy landscapes, the oxidant-bound intermediate serves as the reactant instead of the resting state species. We make this choice because we predict that the resting state would be extremely short-lived following isopropanol release because binding of the oxidant at the open metal site is very favorable (Supporting Information Figures ). We compute barriers for metal-oxo formation and HAT by starting with a relaxed potential energy surface scan, in which we constrain the N-O distance and O-H distance in metal-oxo formation and HAT, respectively, followed by a partitioned rational function optimization (P-RFO) on the highest-energy structure from the scan (see Sec. 3). For HAT, we ensure that we locate transition states associated with an a-radical transfer for Fe catalysts and b-radical transfer for Ru catalysts by inspecting the Mulliken spin densities (Supporting Information Text S4). We assume that the rebound of the isopropyl radical is barrierless and model isopropanol release as an unassisted dissociation followed by rapid binding of 2,6-dichloropyridine 1-oxide, ignoring any kinetic barrier for this ligand exchange. ). The energetic spans, DG for each complex/metal combination assuming spin crossover is allowed are also shown as annotated insets. Of the four catalysts, only the energetic span of D with Ru depends on allowing spin-crossover. The alternative energetic span calculation without spin-crossover is provided in Supporting Information Table .