Shape‐Selective Interception by Hydrocarbons of the O<sub>2</sub>‐Derived Oxidant of a Biomimetic Nonheme Iron Complex

Mukherjee, Anusree; Martinho, Marlène; Bominaar, Emile L.; Münck, Eckard; Que, Lawrence

doi:10.1002/anie.200805342

Cited by 83 publications

(79 citation statements)

References 29 publications

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“…Complex 63a reacted with O 2 to yield a product in which the ortho position of one of the phenyl substituents was hydroxylated [227]; a similar intramolecular hydroxylation was observed for a phenylpyruvate analog (63b) [228]. In subsequent work, the oxidant responsible for this intramolecular process (presumably an Fe(IV)-oxo species) was trapped by exogenous substrates, and the extent of trapping was found to be determined by the molecular shape of the substrate and the strength of the C-H bond being attacked [229]. More recently, decarboxylation of BF and sulfoxidation reactions were observed upon oxygenation of 64 ( Figure 32) in the presence of dimethyl sulfide or dimethyl sulfoxide [230].…”

Section: Monoiron-cofactor Complexes: Catecholates and α-Ketoglutaratesmentioning

confidence: 65%

Transition Metal Complexes and the Activation of Dioxygen

Yee

Tolman

2014

Metal Ions in Life Sciences

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In order to address how diverse metalloprotein active sites, in particular those containing iron and copper, guide O₂binding and activation processes to perform diverse functions, studies of synthetic models of the active sites have been performed. These studies have led to deep, fundamental chemical insights into how O₂coordinates to mono- and multinuclear Fe and Cu centers and is reduced to superoxo, peroxo, hydroperoxo, and, after O-O bond scission, oxo species relevant to proposed intermediates in catalysis. Recent advances in understanding the various factors that influence the course of O₂activation by Fe and Cu complexes are surveyed, with an emphasis on evaluating the structure, bonding, and reactivity of intermediates involved. The discussion is guided by an overarching mechanistic paradigm, with differences in detail due to the involvement of disparate metal ions, nuclearities, geometries, and supporting ligands providing a rich tapestry of reaction pathways by which O₂is activated at Fe and Cu sites.

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Section: Monoiron-cofactor Complexes: Catecholates and α-Ketoglutaratesmentioning

confidence: 65%

Transition Metal Complexes and the Activation of Dioxygen

Yee

Tolman

2014

Metal Ions in Life Sciences

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“…72 A putative Fe IV dO intermediate reacted with fluorene and DHA in 80% yield, but not at all with diphenylmethane, indicating that substrate access to the FedO might be rate-limiting. 73 A recent review describes the range of selectivity factors (including sterics) controlling CÀH activation reactions of organic molecules. 74 The large difference in HAT rates of CHD versus Me 2 CHD and CHD versus dihydronaphthalene with 1 3 t Bupy is among the most sensitive steric constraints observed for HAT reactions.…”

Section: Journal Of the American Chemical Societymentioning

confidence: 99%

Selectivity and Mechanism of Hydrogen Atom Transfer by an Isolable Imidoiron(III) Complex

et al. 2011

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Hydrogen atom transfer (HAT, eq 1) is an elementary chemical transformation that results in the net transfer of both a proton and an electron. 1,2 MetalÀoxo complexes are widely used to abstract hydrogen atoms from organic compounds through HAT, which leads to the metal hydroxide (Scheme 1). 3 In oxidations by cytochrome P450, the mechanism is generally accepted to be HAT to an ironÀoxo species (FedO) followed by radical rebound. 4 Other enzymatic systems such as soluble methane monooxygenase, 5 ribonucleotide reductases and other B 12 -dependent enzymes, 6 lipoxygenases, 7 isopenicillin-N synthase, 8 and TauD 9 also utilize mechanisms with key HAT steps.Considerable effort has been devoted to synthesizing and studying biomimetic oxoiron complexes 10 in order to help elucidate the enzymatic mechanisms and to develop homogeneous iron-based oxidation catalysts. Studies on heme ironÀoxo complexes in the 1980s by Balch, La Mar, and Groves pioneered this field. 11 More recently, Que, Nam, and co-workers have reported isolable non-heme oxoiron(IV) complexes that react with hydrocarbons via HAT. 12 Reactions proceeding by HAT mechanisms have also been studied for terminal oxo complexes of Mn, Ru, Cr, and V. 13À19 In general, the selectivity of nonenzymatic HAT reactions is thermodynamically controlled, and reaction rates follow a linear correlation with the bond dissociation enthalpy (BDE) of the XÀH bond being broken (the BellÀEvansÀPolanyi relation), 1,20 i.e., homolytically weaker substrate bonds react more rapidly.Imido (NR 2À ) ligands are isoelectronic to oxo (O 2À ) ligands (Scheme 1), and imido complexes are often proposed as intermediates in hydrocarbon amination mechanisms in which the imido species performs the cleavage of the CÀH bond that precedes CÀN bond formation. Imido complexes are also more versatile than oxo complexes, because there is an opportunity to tune the steric and electronic properties of the complex by changing the nitrogen substituent. However, the HAT reactivity of imido complexes (MdNR) has not been investigated in as much detail as that of their oxo counterparts. There has been a recent renaissance of activity in the synthesis of imido complexes of the late transition metals (groups 8À11), 21 and this activity has resulted in the isolation of late transition metal complexes Received: January 18, 2011 ABSTRACT: In the literature, ironÀoxo complexes have been isolated and their hydrogen atom transfer (HAT) reactions have been studied in detail. IronÀimido complexes have been isolated more recently, and the community needs experimental evaluations of the mechanism of HAT from late-metal imido species. We report a mechanistic study of HAT by an isolable iron(III) imido complex, L Me FeNAd (L Me = bulky β-diketiminate ligand, 2,4-bis(2,6-diisopropylphenylimido)pentyl; Ad = 1-adamantyl). HAT is preceded by binding of tert-butylpyridine ( t Bupy) to form a reactive fourcoordinate intermediate L Me Fe(NAd)( t Bupy), as shown by equilibrium and kinetic studies. In the HAT step, very la...

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“…[10] The fate of the atomic constituents of dioxygen was determined by 18 [10,11] This hydroxylation reaction can be inhibited by the presence of different reagents that can intercept the putative high-spin Fe IV =O oxidant formed in the oxidative decarboxylation of the iron(II)-benzoylformate complex 2.…”

mentioning

confidence: 99%

Oxidative Decarboxylation of Benzilic Acid by a Biomimetic Iron(II) Complex: Evidence for an Iron(IV)–Oxo–Hydroxo Oxidant from O₂

2011

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Shape‐Selective Interception by Hydrocarbons of the O₂‐Derived Oxidant of a Biomimetic Nonheme Iron Complex

Cited by 83 publications

References 29 publications

Transition Metal Complexes and the Activation of Dioxygen

Transition Metal Complexes and the Activation of Dioxygen

Selectivity and Mechanism of Hydrogen Atom Transfer by an Isolable Imidoiron(III) Complex

Oxidative Decarboxylation of Benzilic Acid by a Biomimetic Iron(II) Complex: Evidence for an Iron(IV)–Oxo–Hydroxo Oxidant from O₂

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Shape‐Selective Interception by Hydrocarbons of the O2‐Derived Oxidant of a Biomimetic Nonheme Iron Complex

Cited by 83 publications

References 29 publications

Transition Metal Complexes and the Activation of Dioxygen

Transition Metal Complexes and the Activation of Dioxygen

Selectivity and Mechanism of Hydrogen Atom Transfer by an Isolable Imidoiron(III) Complex

Oxidative Decarboxylation of Benzilic Acid by a Biomimetic Iron(II) Complex: Evidence for an Iron(IV)–Oxo–Hydroxo Oxidant from O2

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Shape‐Selective Interception by Hydrocarbons of the O₂‐Derived Oxidant of a Biomimetic Nonheme Iron Complex

Oxidative Decarboxylation of Benzilic Acid by a Biomimetic Iron(II) Complex: Evidence for an Iron(IV)–Oxo–Hydroxo Oxidant from O₂