Heme enzymes utilize a redox active heme cofactor containing an iron bound porphyrin in the active site to facilitate chemical transformations in biology. One key species in heme enzymes is a reactive high-valent iron-oxo porphyrin pi-radical cation known as Compound-I (Cpd-I). The coordination of an anionic or neutral axial ligand trans to the oxo group in this species modulates its function. We previously demonstrated that the trianionic, ring-contracted porphyrinoid, TBP8Cz3- (TBP8Cz = octakis(p-tert-butylphenyl)corrolazinato) stabilizes a five-coordinate FeIV(O)(TBP8Cz+•), a Cpd-I analog. In this presentation, the influence of axial ligands on this species will be examined. We generated six-coordinate complexes, FeIV(O)(TBP8Cz+•)(L), where L = 1-methylimidazole, 4-dimethylaminopyridine, and CN-, in situ at low temperature (-80 ℃). Their reactivity toward a hydrogen atom donor, a TEMPOH derivative, was examined, and showed that the nature of the axial ligand dramatically effects their reactivity, CN⁻ causing a ~7000-fold decrease in reaction rate. The mechanism of this reaction was examined with DFT calculations and kinetics measurements including KIE and Eyring analysis. Also described is the synthesis and characterization of related iron chloride corrolazines in the formal +4 and +5 oxidation states. An Fe(IV)Cl complex was prepared by the one electron oxidation of its ferric congener. Characterization by single crystal X-ray diffraction (XRD), Mössbauer, UV-vis, and NMR spectroscopies, as well as mass spectrometry, will be presented. This complex can be oxidized further by a one electron oxidant, and preliminary reactivity studies of these species in H-atom transfer reactions will be discussed.