Characterization and mechanistic study of oxygen-iron intermediates in mononuclear nonheme model systems

The work herein focuses on the chemistry of metastable hydroperoxoiron(III), (eta2-peroxo)iron(III) and oxoiron(IV) species in coordination environments containing either biologically-relevant anionic donors or rigid ligand structures. The spectroscopic characteristics, lifetimes, and decay products of the intermediates generated provide insight into the role of coordination environment in oxygen activation at nonheme iron sites. A better understanding of the mechanisms of nonheme systems may lead to the design of more efficient catalysts for hydrocarbon oxidation.; The reaction of [FeIII(PaPy3)]+, where PaPy3 is an NS ligand with an amidate moiety, with hydrogen peroxide affords [FeIII(PaPy3)(OOH)] +, which decays via a 2-electron process as indicated by a site-specific ligand modification. The proposed mechanism for this decomposition proceeds via heterolytic cleavage of the peroxide O-O bond, similar to that proposed for cytochrome P450. Based on this, a putative oxoiron(V) species is proposed.; The pentadentate N5 ligands Lo and Lu are isomers built upon the rigid bispidine backbone. Lo and Lu differ in the connectivity of the fifth nitrogen ligand, a 2-pyridylmethyl moiety, and Lo provides a weaker ligand field than Lu. These two ligands give rise to hydroperoxoiron(III), (eta2-peroxo)iron(III) and oxoiron(IV) complexes with different stabilities, which increase with the strength of the ligand field.; The approximately square-planar L8Py2 ligand affords high-spin alkylperoxoiron(III) complexes with a site that allows coordination of a variable sixth ligand trans to the alkylperoxo moiety. As the basicity of the ligand at this site increases, the lifetime of the alkylperoxoiron(III) intermediate increases. The reaction of [FeII (L8Py2)(OTf)](OTf) in acetonitrile with alkylperoxides yields an oxoiron(IV) species that originates from heterolysis of the peroxide O-O bond, similar to the reaction proposed for pterin-dependent hydroxylases.; The complex [FeII(TMCS)](PF6) has a square pyramidal N4-SR coordination sphere that models the active site of superoxide reductase. The reaction of [FeII(TMCS)](PF 6) with hydrogen peroxide generates an oxoiron(IV)-SR species with intense visible chromophores, unlike other oxoiron(IV) species characterized to date. A second oxoiron(IV) species was characterized in which the thiolate ligand was oxidized to a sulfinate moiety. The spectroscopic characteristics and lifetimes of these intermediates are explored.