A synthetic precedent for the [Fe
 IV
 2
 (μ-O)
 2
 ] diamond core proposed for methane monooxygenase intermediate Q

Xue, Genqiang; Wang, Dong; Hont, Raymond De; Fiedler, Adam T.; Shan, Xuechuan; Münck, Eckard; Que, Lawrence

doi:10.1073/pnas.0708516105

Cited by 152 publications

(220 citation statements)

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“…A detailed analysis of EXAFS and Mössbauer spectroscopic data revealed that Q is best described as a strongly exchange-coupled S = 2 diiron(IV) species with an Fe-Fe distance of 2.46 Å and pairs of short and long Fe-O bonds of 1.77 and 2.05 Å, respectively, consistent with an Fe 2 IV (µ-O) 2 -diamond core structure 70 . Xue et al 71 (Fig. 5c) showed that the terminal iron(IV) oxo units are at least three orders of magnitude more reactive than the ones with diamond cores 74 .…”

Section: Dinuclear Bis(µ-oxo)diiron(iv) Model Complexesmentioning

confidence: 96%

The biology and chemistry of high-valent iron–oxo and iron–nitrido complexes

2012

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selective functionalization of unactivated c-H bonds and ammonia production are extremely important industrial processes. a range of metalloenyzmes achieve these challenging tasks in biology by activating dioxygen and dinitrogen using cheap and abundant transition metals, such as iron, copper and manganese. High-valent iron-oxo and -nitrido complexes act as active intermediates in many of these processes. the generation of well-described model compounds can provide vital insights into the mechanism of such enzymatic reactions. advances in the chemistry of model high-valent iron-oxo and -nitrido systems can be related to our understanding of the biological systems.H igh-valent oxoiron(IV) and formally oxoiron(V) species have been spectroscopically identified as active intermediates in the catalytic cycles of a number of enzymatic systems 1-10 . Haem and non-haem proteins use these reactive intermediates to couple the activation of dioxygen to the oxidation of their substrates. In most cases, an oxygen atom is inserted into an unactivated C-H bond of the substrate; for example, in hydroxylation reactions [1][2][3][4][5][6][7][8][9][10] . However, many other reactions, including halogenation, desaturation, cyclization, epoxidation and decarboxylation, are also known to involve oxoiron species 1,3 . Superoxidized iron complexes with (valence) isoelectronic imido and nitrido ligands, as well as 'surface nitrides' , have also been implicated as key intermediates in the nitrogen atom transfer reactions 11 , the biological synthesis of ammonia by the nitrogenase enzyme 12-16 and the industrial Haber-Bosch process 17 .The generation of well-described model compounds can provide vital insights into the mechanism of such enzymatic reactions. Consequently, considerable effort has been made by synthetic chemists to prepare viable models for the putative reaction intermediates in the catalytic cycles of O 2 and N 2 activating enzymes. In this review, we provide an overview of all high-valent oxoiron and nitridoiron species that have been either identified or proposed as reactive intermediates in biology. Subsequently, we summarize some of the recent advances in bioinorganic chemistry that have led to the identification and isolation of iron complexes in unusually high formal oxidation states, containing iron-oxygen or iron-nitrogen multiple bonds. The spectroscopic characterization and the reactivity studies of these model complexes provide vital insights into the mechanism that nature uses to induce the reductive cleavage of dioxygen or dinitrogen in carrying out a number of important biochemical oxidative transformations. Moreover, the comparative review of the electronic structures of the isoelectronic oxoiron and nitridoiron functionalities reveals that the Fe-N bonds are intrinsically more covalent than the Fe-O bonds.

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Section: Dinuclear Bis(µ-oxo)diiron(iv) Model Complexesmentioning

confidence: 96%

The biology and chemistry of high-valent iron–oxo and iron–nitrido complexes

2012

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“…(30), contains a monoμ-oxo bridged diiron center that has two additional amide bridges that model the carboxylate bridges of the biFe enzymes. Its Fe(III)Fe(III) form has been crystallized, and its conversions to the Fe(III)Fe(IV) and Fe(IV) 2 2 ] can be converted to the Fe(IV) 2 form by either electrolysis or chemical oxidation using WCl 6 , without undergoing any structural disruption according to their EXAFS spectra (31).…”

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confidence: 99%

“…Similarly, the di-oxo bridged low-spin Fe(IV) 2 and Fe(III)Fe(IV) complexes 2 were prepared from a high-spin Fe(III) 2 precursor (31,32). Again, although the major NRVS features of the high-valent complexes of 2 are in the energy region between 200 and 450 cm −1 , those of the Fe(III) 2 precursor appear at lower energy between 200 and 300 cm −1 (Fig.…”

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confidence: 99%

Nuclear resonance vibrational spectroscopic and computational study of high-valent diiron complexes relevant to enzyme intermediates

Park

Bell

Liu

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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High-valent intermediates of binuclear nonheme iron enzymes are structurally unknown despite their importance for understanding enzyme reactivity. Nuclear resonance vibrational spectroscopy combined with density functional theory calculations has been applied to structurally well-characterized high-valent mono-and di-oxo bridged binuclear Fe model complexes. Low-frequency vibrational modes of these high-valent diiron complexes involving Fe motion have been observed and assigned. These are independent of Fe oxidation state and show a strong dependence on spin state. It is important to note that they are sensitive to the nature of the Fe 2 core bridges and provide the basis for interpreting parallel nuclear resonance vibrational spectroscopy data on the highvalent oxo intermediates in the binuclear nonheme iron enzymes.iron-oxo cores | Fe enzymes C lass Ia ribonucleotide reductase (RR) (1) and soluble methane monooxygenase (sMMO) (2) are members of the class of binuclear nonheme iron enzymes. These have intrigued researchers due to their significance in the development of anticancer drugs (RR) (3) and biofuel catalysts (sMMO) (4) and their varied reactivities using a conserved 2 His/4 carboxylate ligand set. These enzymes use a biFe active site to activate O 2 for hydrogen atom abstraction and hydroxylation via key high-valent intermediates called X (5, 6) and Q (7, 8) in RR and sMMO, respectively.

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“…Consequently, considerable effort has been made by synthetic chemists to prepare viable models for the putative reaction intermediates in the catalytic cycles of O 2 -activating enzymes. Although in the case of MMO these efforts culminated in a number of structurally characterized model complexes that closely mimic the geometric and spectroscopic properties of several intermediates participating in the catalytic cycle of the enzyme (4, 9), a synthetic precedent for the [Fe IV 2 ( -O) 2 ] diamond core proposed for MMO-Q had been lacking prior to the work of Xue et al (8). For this reason, relatively little is currently known about the geometric and electronic structures of this powerful oxidant.…”

mentioning

confidence: 99%

“…Another important aspect of the work of Xue et al (8) is that it provides a suitable basis for the pursuit of a number of different research avenues pertaining to the mechanism of O 2 activation and substrate oxidation by diiron centers. First, carrying out detailed studies of the reactivity of this model complex will provide invaluable information regarding the mechanism by which enzyme intermediates possessing an [Fe IV 2 ( -O) 2 ] diamond core oxidize organic substrates.…”

mentioning

confidence: 99%

Synthetic iron-oxo “diamond core” mimics structure of key intermediate in methane monooxygenase catalytic cycle

Brunold

2007

Proc. Natl. Acad. Sci. U.S.A.

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A synthetic precedent for the [Fe ^IV ₂ (μ-O) ₂ ] diamond core proposed for methane monooxygenase intermediate Q

Cited by 152 publications

References 45 publications

The biology and chemistry of high-valent iron–oxo and iron–nitrido complexes

The biology and chemistry of high-valent iron–oxo and iron–nitrido complexes

Nuclear resonance vibrational spectroscopic and computational study of high-valent diiron complexes relevant to enzyme intermediates

Synthetic iron-oxo “diamond core” mimics structure of key intermediate in methane monooxygenase catalytic cycle

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A synthetic precedent for the [Fe IV 2 (μ-O) 2 ] diamond core proposed for methane monooxygenase intermediate Q

Cited by 152 publications

References 45 publications

The biology and chemistry of high-valent iron–oxo and iron–nitrido complexes

The biology and chemistry of high-valent iron–oxo and iron–nitrido complexes

Nuclear resonance vibrational spectroscopic and computational study of high-valent diiron complexes relevant to enzyme intermediates

Synthetic iron-oxo “diamond core” mimics structure of key intermediate in methane monooxygenase catalytic cycle

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A synthetic precedent for the [Fe ^IV ₂ (μ-O) ₂ ] diamond core proposed for methane monooxygenase intermediate Q