Fast Water Oxidation Using Iron

Ellis, W. Chadwick; McDaniel, Neal D.; Bernhard, Stefan; Collins, Terrence J.

doi:10.1021/ja104766z

Cited by 598 publications

(448 citation statements)

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“…1 top and an I2M mechanism is found when the favored species resemble those of the oxyl radical form depicted in the lower part of Figure 1 Recently several first row transition metal complexes have been reported as catalysts for the water oxidation reaction. [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40] While these catalysts are of interest because of their high abundance and low toxicity, their performance is much poorer than their Ru or Ir analogues, and in addition their mechanistic pathways are in most cases basically unknown. [28][29][30][41][42][43] We have very recently reported a new complex based on Cu, containing the amidate ligand OPBAN that can carry out the water oxidation reaction in a very efficient manner.…”

Section: Introductionmentioning

confidence: 99%

Single Electron Transfer Steps in Water Oxidation Catalysis. Redefining the Mechanistic Scenario

et al. 2017

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Section: Introductionmentioning

confidence: 99%

Single Electron Transfer Steps in Water Oxidation Catalysis. Redefining the Mechanistic Scenario

et al. 2017

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“…Citing just a small portion of the broad interest in molecular water oxidation: ruthenium dimers [9][10][11][12] and tetramers, [13][14][15] cobalt tetramers, 16,17 manganese dimers 18 along with recent work detailing single-site catalysts [19][20][21][22][23][24][25][26] all illustrate the diversity of successful catalysts. More recently, a variety of Cp*Ir complexes (Cp* = C 5 Me 5 -) have been shown to act as efficient water oxidation precatalysts.…”

Section: Introductionmentioning

confidence: 99%

Carbene iridium complexes for efficient water oxidation: scope and mechanistic insights

Woods

Lalrempuia

Petronilho

et al. 2014

Energy Environ. Sci.

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107

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Iridium complexes of Cp* and mesoionic carbene ligands were synthesized and evaluated as potential water oxidation catalysts using cerium ammonium nitrate as a chemical oxidant. Performance was evaluated by turnover frequency at 50% conversion and by absolute turnover number, and the most promising precatalysts were subjected to further study. Molecular turnover frequencies varied from 190 to 451 per hour with a maximum turnover number of 38,000. While the rate of oxygen evolution depends linearly on iridium concentration, 10 concurrent spectroscopic and manometric monitoring of stoichiometric additions of oxidant suggests oxygen evolution occurs as two sequential first order reactions. Under the conditions herein, the oxygen evolving species appears to be well defined and molecular based on the kinetic effects of careful ligand design, reproducibility, and the absence of persistent dynamic light scattering signals. Outside of these conditions, the complex mechanism is highly dependent on reaction conditions. While confident characterization of the catalytically active species is difficult, especially under high-turnover conditions, this work indicates IrOx is not essential for the 15 formation of catalytically active water oxidation species.

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“…Accordingly, Tiago de Oliveira et al 32 reported the synthesis of an oxoiron(V) ( An Fe V (O)(OH) species has been implicated as the active oxidant responsible for the cis-dihydroxylation of C = C double bonds 2,4,33 and the oxidation of water 34 in a number of ironcontaining non-haem natural and model systems, but with only indirect proof of its existence [35][36][37] . However, the spectroscopically characterized [(TAML)Fe V (O)] − anion, which is the only known isolable oxoiron(V) species in the literature, was found to be a sluggish oxidant 32 38 . Therefore, the involvement of Fe V (O)(OH) intermediates in oxygenation reactions remained doubtful until very recently 39 .…”

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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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Fast Water Oxidation Using Iron

Cited by 598 publications

References 19 publications

Single Electron Transfer Steps in Water Oxidation Catalysis. Redefining the Mechanistic Scenario

Single Electron Transfer Steps in Water Oxidation Catalysis. Redefining the Mechanistic Scenario

Carbene iridium complexes for efficient water oxidation: scope and mechanistic insights

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

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