Synthetic non-heme FeIV(O) complexes have emerged as powerful tools for elucidating the relationship between chemical environment and reactivity of short-lived non-heme FeIV(O) intermediates found within biological enzymes.1 To further this effort, the effects of ligand environment on synthetic FeIV(O) complexes has been probed in two different contexts - reactivity with organic molecules and rates of oxygen-atom exchange (OAE) with H218O.A synthetic non-heme FeIV(O) complex, [FeIV(O)(Bn-tpen)]2+ (where Bn-tpen = N-benzyl-N,N',N'-tris(2-pyridylmethyl)-1,2-diaminoethane) has previously been shown capable of oxidizing the strong C-H bonds of cyclohexane (BDE = 99 kcal/mol).2 We have synthesized two variants of Bn-tpen, one in which a pyridine ring has been replaced by a quinoline ring, Q-Bn-tpen, and the other in which the same pyridine ring has been replaced by a 6-methylpyridine ring, 6Me-Bn-tpen. Reaction of corresponding FeIV(O) compounds, [FeIV(O)(Q-Bn-tpen)]2+ and [FeIV(O)(6Me-Bn-tpen)]2+, with organic substrates, such as thioanisole, revealed a fifty-fold increase in oxidation rates compared to the parent complex, [FeIV(O)(Bn-tpen)]2+. A discussion for this increase in reactivity will be presented.Additionally, the effects of ligand environment on the kinetics of oxygen-atom exchange between synthetic non-heme FeIV(O) complexes and H218O was investigated through electrospray ionization mass spectrometry.3,4 These studies reveal that the denticity of the supporting ligand has a profound effect on the overall mechanism, where OAE with FeIV(O) complexes supported by tetradentate and pentadentate ligands appear to have two distinct rate-determining steps.  McDonald, et al. Coord. Chem. Rev. 2013 , 257, 414 � 428.Kaizer, et al. J. Am. Chem. Soc. 2004 , 126, 472 � 473.Seo, et al. Angew. Chem. 2004 , 116, 2471 � 2474.Company, et al. Chem. Eur. J. 2011 , 17, 1622 � 1634.

Ligand dependence on the reactivity of synthetic non-heme Fe<sup>IV</sup>(O) complexes

248th National Meeting (2014)

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Ligand dependence on the reactivity of synthetic non-heme FeIV(O) complexes

Ligand dependence on the reactivity of synthetic non-heme Fe^IV(O) complexes