Structural- and Spectroscopic-Reactivity Relationships of Nonheme Oxoiron(IV) Complexes

Abstract

Non-heme oxoiron(IV) motifs have been identified as key intermediates that activate strong C—H bonds. Unlike the enzymatic intermediates however, most oxoiron(IV) complexes in synthetic chemistry have a triplet ground spin state and thus differ in their functional and electronic properties from the S = 2 units characterized in the enzymes. One striking exception is the complex [FeIV(O)(TQA)(L)]2+, where TQA = tris(2-quinolylmethyl)amine, which has Mössbauer parameters that closely resemble those of TauD-J, an enzymatic intermediate that has been relatively well-characterized. This oxoiron(IV) complex contains quinoline donors, and its thermal instability precludes its structural characterization (half-life = 15 minutes at 233 K). In this dissertation, several oxoiron(IV) complexes supported by pentadentate and tetradentate ligands are characterized, and examined for their reactivity and spectroscopic features. Crystallographic characterization of a few of these molecules is also reported. The structurally characterized oxoiron(IV) complexes along with some previously reported oxoiron(IV) complexes are used to set up structure-reactivity and spectroscopic-reactivity relationships, and show linear correlations with increasing isomer shifts, λmax values as well as metal-ligand distances. In addition, this thesis also uses 1H-NMR spectroscopy as an effective tool to identify solution-state structure as well the spin state of oxoiron(IV) complexes. We also characterize the first example of a spin crossover oxoiron(IV) complex, examples of which are only seen in iron(II) and iron(III) complexes.