Top: Ligands used in this study that are proposed to support nonheme FeV(O) intermediates. Bottom: Various metal species involved in this study. The labelling scheme used throughout the text combines numbers that designate the metal species with letters that designate the ligands. For example, for complexes supported by TPA, the (L)FeII complex = 1a, (L)FeIII-OOH = 2a, (L)FeIII-OOAc = 3a, (L)FeIV(O)(•OAc) = 4a, and (L)FeV(O)(OAc) = 5a.