In the case of a hexa-coordinated iron active site with bidentate succinate, Asp/Glu is monodentate, and the oxo or hydroxo moieties can be present in axial or equatorial positions, resulting in two configurational isomers (Figure and Supporting Information Figure ). Two such isomers can also be constructed when Asp/Glu is bidentate and succinate is monodentate (Figure and Supporting Information Figure ). Additionally, these two configurational isomers can be formed when we have a penta-coordinated iron active site where both succinate and Asp/Glu are monodentate (Figure and Supporting Information Figure ). Overall, given that both succinate and Asp/Glu can bind to iron in either a monodentate or bidentate fashion, we potentially have a total of six configurational isomers for intermediates (3) and (4) (Figure and Supporting Information Figure ).