Nonheme oxoiron(IV) intermediates are proposed to be involved in a number of important biological oxidation reactions, where all characterized examples thus far have a S = 2 ground spin state. In contrast, the majority of synthetic nonheme oxoiron(IV) complexes have a S = 1 ground spin state. In order to gain a deeper understanding of these important biological species, it is critical to expand the number of synthetic S = 2 nonheme oxoiron(IV) complexes and to study their reactivity with organic substrates. This thesis explores a synthetic strategy to obtain S = 2 nonheme oxoiron(IV) complexes by utilizing weak-field equatorial quinoline donors, in contrast to the relatively strong-field pyridine donors that are often used. The resulting S = 2 nonheme oxoiron(IV) complexes demonstrate spectroscopic signatures similar to those of the enzymatic oxoiron(IV) intermediates and reproduce the reactivity observed by these nonheme iron enzymes. Thus, this research has given rise to the first electronic and functional models of the nonheme oxoiron(IV) intermediates found in the enzymes TauD, CytC3 and SyrB2. In addition, the reactivity of known S = 1 nonheme oxoiron(IV) complexes were explored in the context of oxygen-atom exchange with H2O, which is an important reaction in tracking metal-oxo intermediates proposed to be involved in catalytic substrate oxidation reactions. Finally, a six-coordinate S = 1 nonheme imidoiron(IV) complex supported by a tetradentate ligand was synthesized and compared to its isoelectronic S = 1 nonheme oxoiron(IV) analogue.