The reactions catalyzed by nonheme iron enzymes typically proceed through FeOOH(R) and Fe(O) intermediates. Aromatic amino acid hydroxylases are a class of nonheme iron enzymes which catalyzes the arene hydroxylation of amino acid residues. We have synthesized two new ligands, N4Py2Ph and N4Py2Ph,amide, which provide phenyl groups tethered in the 2nd coordination sphere as potential substrates for arene hydroxylation. The iron(II) complexes of both the ligands were prepared and structurally characterized. The FeII complex [FeII(N4Py2Ph)(CH3CN)](BF4)2 undergoes intramolecular arene hydroxylation upon reaction with oxidants such as tBuOOH and IBX-ester via a proposed FeIV(O) intermediate. In contrast, no intermolecular arene hydroxylation occurs for the analogous unsubstituted N4Py system. Computational studies provide a rationale for the observed facile intramolecular arene hydroxylation, and the DFT results indicate that the positioning of the phenyl group in the 2nd coordination sphere is essential for the reactivity. The presence of an H-bond donating amide group in [FeII(N4Py2Ph,amide)](BF4)2 inhibits arene hydroxylation, and leads to formation of a high-spin FeIIIOOR complex at low temperature.

Experimental and computational studies on the influence of secondary coordination sphere elements in arene hydroxylation by nonheme iron complexes

248th National Meeting (2014)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.