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Abstract
An enormous variety of biological redox reactions are accompanied by changes in proton content at enzyme active sites, in their associated cofactors, in substrates and/or products, and between protein interfaces. Understanding this breadth of reactivity is an ongoing chemical challenge. A great many workers have developed and investigated biomimetic model complexes to build new ways of thinking about the mechanistic underpinnings of such complex biological proton-coupled electron transfer (PCET) reactions. Of particular importance are those model reactions that involve transfer of one proton (H(+)) and one electron (e(-)), which is equivalent to transfer of a hydrogen atom (H(•)). In this Current Topic, we review key concepts in PCET reactivity and describe important advances in biomimetic PCET chemistry, with a special emphasis on research that has enhanced efforts to understand biological PCET reactions.
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Affiliation(s)
- Jeffrey J. Warren
- Simon Fraser University, Department of Chemistry, 8888 University Drive, Burnaby BC, Canada V5A 1S6
| | - James M. Mayer
- Yale University, Department of Chemistry, P.O. Box 208107, 225 Prospect Street, New Haven, CT 06520-8107
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102
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Kleespies ST, Oloo WN, Mukherjee A, Que L. C-H Bond Cleavage by Bioinspired Nonheme Oxoiron(IV) Complexes, Including Hydroxylation of n-Butane. Inorg Chem 2015; 54:5053-64. [PMID: 25751610 DOI: 10.1021/ic502786y] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The development of efficient and selective hydrocarbon oxidation processes with low environmental impact remains a major challenge of the 21st century because of the strong and apolar nature of the C-H bond. Naturally occurring iron-containing metalloenzymes can, however, selectively functionalize strong C-H bonds on substrates under mild and environmentally benign conditions. The key oxidant in a number of these transformations is postulated to possess an S = 2 Fe(IV)═O unit in a nonheme ligand environment. This oxidant has been trapped and spectroscopically characterized and its reactivity toward C-H bonds demonstrated for several nonheme iron enzyme classes. In order to obtain insight into the structure-activity relationships of these reactive intermediates, over 60 synthetic nonheme Fe(IV)(O) complexes have been prepared in various laboratories and their reactivities investigated. This Forum Article summarizes the current status of efforts in the characterization of the C-H bond cleavage reactivity of synthetic Fe(IV)(O) complexes and provides a snapshot of the current understanding of factors that control this reactivity, such as the properties of the supporting ligands and the spin state of the iron center. In addition, new results on the oxidation of strong C-H bonds such as those of cyclohexane and n-butane by a putative S = 2 synthetic Fe(IV)(O) species that is generated in situ using dioxygen at ambient conditions are presented.
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Affiliation(s)
- Scott T Kleespies
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Williamson N Oloo
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Anusree Mukherjee
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Lawrence Que
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota 55455, United States
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103
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Lo WK, McAdam CJ, Blackman AG, Crowley JD, McMorran DA. The pentadentate ligands 2PyN2Q and N4Py, and their Cu(II) and Zn(II) complexes: A synthetic, spectroscopic and crystallographic structural study. Inorganica Chim Acta 2015. [DOI: 10.1016/j.ica.2014.11.036] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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104
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Codolà Z, Gómez L, Kleespies ST, Que L, Costas M, Lloret-Fillol J. Evidence for an oxygen evolving iron-oxo-cerium intermediate in iron-catalysed water oxidation. Nat Commun 2015; 6:5865. [PMID: 25609387 DOI: 10.1038/ncomms6865] [Citation(s) in RCA: 113] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2014] [Accepted: 11/17/2014] [Indexed: 02/08/2023] Open
Abstract
The non-haem iron complex α-[Fe(II)(CF3SO3)2(mcp)] (mcp=(N,N'-dimethyl-N,N'-bis(2-pyridylmethyl)-1,2-cis-diaminocyclohexane) reacts with Ce(IV) to oxidize water to O2, representing an iron-based functional model for the oxygen evolving complex of photosystem II. Here we trap an intermediate, characterized by cryospray ionization high resolution mass spectrometry and resonance Raman spectroscopy, and formulated as [(mcp)Fe(IV)(O)(μ-O)Ce(IV)(NO3)3](+), the first example of a well-characterized inner-sphere complex to be formed in cerium(IV)-mediated water oxidation. The identification of this reactive Fe(IV)-O-Ce(IV) adduct may open new pathways to validate mechanistic notions of an analogous Mn(V)-O-Ca(II) unit in the oxygen evolving complex that is responsible for carrying out the key O-O bond forming step.
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Affiliation(s)
- Zoel Codolà
- Institut de Química Computacional i Catàlisi (IQCC) and Departament de Química, Universitat de Girona, Campus de Montilivi, 17071 Girona, Spain
| | - Laura Gómez
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant St S.E., Minneapolis, Minnesota 55455, USA
| | - Scott T Kleespies
- Serveis Tècnics de Recerca (STR), Parc Cientific i Tecnològic, Universitat de Girona, 17003 Girona, Spain
| | - Lawrence Que
- Serveis Tècnics de Recerca (STR), Parc Cientific i Tecnològic, Universitat de Girona, 17003 Girona, Spain
| | - Miquel Costas
- Institut de Química Computacional i Catàlisi (IQCC) and Departament de Química, Universitat de Girona, Campus de Montilivi, 17071 Girona, Spain
| | - Julio Lloret-Fillol
- Institut de Química Computacional i Catàlisi (IQCC) and Departament de Química, Universitat de Girona, Campus de Montilivi, 17071 Girona, Spain
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105
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Faponle AS, Quesne MG, Sastri CV, Banse F, de Visser SP. Differences and comparisons of the properties and reactivities of iron(III)-hydroperoxo complexes with saturated coordination sphere. Chemistry 2015; 21:1221-36. [PMID: 25399782 PMCID: PMC4316188 DOI: 10.1002/chem.201404918] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Indexed: 11/06/2022]
Abstract
Heme and nonheme monoxygenases and dioxygenases catalyze important oxygen atom transfer reactions to substrates in the body. It is now well established that the cytochrome P450 enzymes react through the formation of a high-valent iron(IV)-oxo heme cation radical. Its precursor in the catalytic cycle, the iron(III)-hydroperoxo complex, was tested for catalytic activity and found to be a sluggish oxidant of hydroxylation, epoxidation and sulfoxidation reactions. In a recent twist of events, evidence has emerged of several nonheme iron(III)-hydroperoxo complexes that appear to react with substrates via oxygen atom transfer processes. Although it was not clear from these studies whether the iron(III)-hydroperoxo reacted directly with substrates or that an initial O-O bond cleavage preceded the reaction. Clearly, the catalytic activity of heme and nonheme iron(III)-hydroperoxo complexes is substantially different, but the origins of this are still poorly understood and warrant a detailed analysis. In this work, an extensive computational analysis of aromatic hydroxylation by biomimetic nonheme and heme iron systems is presented, starting from an iron(III)-hydroperoxo complex with pentadentate ligand system (L5(2)). Direct C-O bond formation by an iron(III)-hydroperoxo complex is investigated, as well as the initial heterolytic and homolytic bond cleavage of the hydroperoxo group. The calculations show that [(L5(2))Fe(III)(OOH)](2+) should be able to initiate an aromatic hydroxylation process, although a low-energy homolytic cleavage pathway is only slightly higher in energy. A detailed valence bond and thermochemical analysis rationalizes the differences in chemical reactivity of heme and nonheme iron(III)-hydroperoxo and show that the main reason for this particular nonheme complex to be reactive comes from the fact that they homolytically split the O-O bond, whereas a heterolytic O-O bond breaking in heme iron(III)-hydroperoxo is found.
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Affiliation(s)
- Abayomi S Faponle
- Manchester Institute of Biotechnology and School of Chemical Engineering and Analytical Science, The University of Manchester131 Princess Street, Manchester M1 7DN (UK) E-mail:
| | - Matthew G Quesne
- Manchester Institute of Biotechnology and School of Chemical Engineering and Analytical Science, The University of Manchester131 Princess Street, Manchester M1 7DN (UK) E-mail:
| | - Chivukula V Sastri
- Department of Chemistry, Indian Institute of Technology Guwahati781039, Assam (India)
| | - Frédéric Banse
- Institut de Chimie Moleculaire et des Materiaux d'Orsay, Laboratoire de Chimie Inorganique, Université Paris-Sud11 91405 Orsay Cedex (France) E-mail:
| | - Sam P de Visser
- Manchester Institute of Biotechnology and School of Chemical Engineering and Analytical Science, The University of Manchester131 Princess Street, Manchester M1 7DN (UK) E-mail:
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106
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Ségaud N, Anxolabéhère-Mallart E, Sénéchal-David K, Acosta-Rueda L, Robert M, Banse F. Electrochemical study of a nonheme Fe(ii) complex in the presence of dioxygen. Insights into the reductive activation of O 2 at Fe(ii) centers. Chem Sci 2015; 6:639-647. [PMID: 28936313 PMCID: PMC5588783 DOI: 10.1039/c4sc01891e] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2014] [Accepted: 09/16/2014] [Indexed: 01/15/2023] Open
Abstract
Recent efforts to model the reactivity of iron oxygenases have led to the generation of nonheme FeIII(OOH) and FeIV(O) intermediates from FeII complexes and O2 but using different cofactors. This diversity emphasizes the rich chemistry of nonheme Fe(ii) complexes with dioxygen. We report an original mechanistic study of the reaction of [(TPEN)FeII]2+ with O2 carried out by cyclic voltammetry. From this FeII precursor, reaction intermediates such as [(TPEN)FeIV(O)]2+, [(TPEN)FeIII(OOH)]2+ and [(TPEN)FeIII(OO)]+ have been chemically generated in high yield, and characterized electrochemically. These electrochemical data have been used to analyse and perform simulation of the cyclic voltammograms of [(TPEN)FeII]2+ in the presence of O2. Thus, several important mechanistic informations on this reaction have been obtained. An unfavourable chemical equilibrium between O2 and the FeII complex occurs that leads to the FeIII-peroxo complex upon reduction, similarly to heme enzymes such as P450. However, unlike in heme systems, further reduction of this latter intermediate does not result in O-O bond cleavage.
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Affiliation(s)
- Nathalie Ségaud
- Institut de Chimie Moléculaire et des Matériaux d'Orsay , UMR CNRS 8182 , Université Paris Sud , F-91405 Orsay Cedex , France .
| | - Elodie Anxolabéhère-Mallart
- Laboratoire d'Electrochimie Moléculaire , Université Paris Diderot , Sorbonne Paris Cité , F-75205 PARIS CEDEX 13 , France .
| | - Katell Sénéchal-David
- Institut de Chimie Moléculaire et des Matériaux d'Orsay , UMR CNRS 8182 , Université Paris Sud , F-91405 Orsay Cedex , France .
| | - Laura Acosta-Rueda
- Institut de Chimie Moléculaire et des Matériaux d'Orsay , UMR CNRS 8182 , Université Paris Sud , F-91405 Orsay Cedex , France .
| | - Marc Robert
- Laboratoire d'Electrochimie Moléculaire , Université Paris Diderot , Sorbonne Paris Cité , F-75205 PARIS CEDEX 13 , France .
| | - Frédéric Banse
- Institut de Chimie Moléculaire et des Matériaux d'Orsay , UMR CNRS 8182 , Université Paris Sud , F-91405 Orsay Cedex , France .
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107
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108
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Saucedo-Vázquez JP, Kroneck PMH, Sosa-Torres ME. The role of molecular oxygen in the iron(iii)-promoted oxidative dehydrogenation of amines. Dalton Trans 2015; 44:5510-9. [DOI: 10.1039/c4dt03606a] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A mechanistic study is presented of the oxidative dehydrogenation of the iron(iii) complex [FeIIIL3]3+, 1, (L3 = 1,9-bis(2′-pyridyl)-5-[(ethoxy-2′′-pyridyl)methyl]-2,5,8-triazanonane) in ethanol in the presence of molecular oxygen.
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Affiliation(s)
- Juan Pablo Saucedo-Vázquez
- Departamento de Química Inorgánica y Nuclear
- Facultad de Química
- Universidad Nacional Autónoma de México
- Ciudad Universitaria
- México, D.F. 04510
| | | | - Martha Elena Sosa-Torres
- Departamento de Química Inorgánica y Nuclear
- Facultad de Química
- Universidad Nacional Autónoma de México
- Ciudad Universitaria
- México, D.F. 04510
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109
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Barbieri A, De Gennaro M, Di Stefano S, Lanzalunga O, Lapi A, Mazzonna M, Olivo G, Ticconi B. Isotope effect profiles in the N-demethylation of N,N-dimethylanilines: a key to determine the pKa of nonheme Fe(iii)–OH complexes. Chem Commun (Camb) 2015; 51:5032-5. [DOI: 10.1039/c5cc00411j] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
pKa of [(N4Py)FeIII–OH]2+ is obtained from the kinetic isotope effect profiles in the N-demethylation of N,N-dimethylanilines promoted by [(N4Py)FeIVO]2+.
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Affiliation(s)
- Alessia Barbieri
- Dipartimento di Chimica
- Sapienza Università di Roma and Istituto CNR di Metodologie Chimiche (IMC-CNR)
- Sezione Meccanismi di Reazione
- c/o Dipartimento di Chimica
- Sapienza Università di Roma
| | - Martina De Gennaro
- Dipartimento di Chimica
- Sapienza Università di Roma and Istituto CNR di Metodologie Chimiche (IMC-CNR)
- Sezione Meccanismi di Reazione
- c/o Dipartimento di Chimica
- Sapienza Università di Roma
| | - Stefano Di Stefano
- Dipartimento di Chimica
- Sapienza Università di Roma and Istituto CNR di Metodologie Chimiche (IMC-CNR)
- Sezione Meccanismi di Reazione
- c/o Dipartimento di Chimica
- Sapienza Università di Roma
| | - Osvaldo Lanzalunga
- Dipartimento di Chimica
- Sapienza Università di Roma and Istituto CNR di Metodologie Chimiche (IMC-CNR)
- Sezione Meccanismi di Reazione
- c/o Dipartimento di Chimica
- Sapienza Università di Roma
| | - Andrea Lapi
- Dipartimento di Chimica
- Sapienza Università di Roma and Istituto CNR di Metodologie Chimiche (IMC-CNR)
- Sezione Meccanismi di Reazione
- c/o Dipartimento di Chimica
- Sapienza Università di Roma
| | - Marco Mazzonna
- Dipartimento di Chimica
- Sapienza Università di Roma and Istituto CNR di Metodologie Chimiche (IMC-CNR)
- Sezione Meccanismi di Reazione
- c/o Dipartimento di Chimica
- Sapienza Università di Roma
| | - Giorgio Olivo
- Dipartimento di Chimica
- Sapienza Università di Roma and Istituto CNR di Metodologie Chimiche (IMC-CNR)
- Sezione Meccanismi di Reazione
- c/o Dipartimento di Chimica
- Sapienza Università di Roma
| | - Barbara Ticconi
- Dipartimento di Chimica
- Sapienza Università di Roma and Istituto CNR di Metodologie Chimiche (IMC-CNR)
- Sezione Meccanismi di Reazione
- c/o Dipartimento di Chimica
- Sapienza Università di Roma
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110
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Barman P, Vardhaman AK, Martin B, Wörner SJ, Sastri CV, Comba P. Influence of ligand architecture on oxidation reactions by high-valent nonheme manganese oxo complexes using water as a source of oxygen. Angew Chem Int Ed Engl 2014; 54:2095-9. [PMID: 25557423 DOI: 10.1002/anie.201409476] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2014] [Revised: 11/17/2014] [Indexed: 11/07/2022]
Abstract
Mononuclear nonheme Mn(IV)=O complexes with two isomers of a bispidine ligand have been synthesized and characterized by various spectroscopies and density functional theory (DFT). The Mn(IV)=O complexes show reactivity in oxidation reactions (hydrogen-atom abstraction and sulfoxidation). Interestingly, one of the isomers (L(1) ) is significantly more reactive than the other (L(2) ), while in the corresponding Fe(IV)=O based oxidation reactions the L(2) -based system was previously found to be more reactive than the L(1) -based catalyst. This inversion of reactivities is discussed on the basis of DFT and molecular mechanics (MM) model calculations, which indicate that the order of reactivities are primarily due to a switch of reaction channels (σ versus π) and concomitant steric effects.
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Affiliation(s)
- Prasenjit Barman
- Department of Chemistry, Indian Institute of Technology Guwahati, Assam, 781039 (India)
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111
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Barman P, Vardhaman AK, Martin B, Wörner SJ, Sastri CV, Comba P. Influence of Ligand Architecture on Oxidation Reactions by High-Valent Nonheme Manganese Oxo Complexes Using Water as a Source of Oxygen. Angew Chem Int Ed Engl 2014. [DOI: 10.1002/ange.201409476] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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112
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Geng C, Ye S, Neese F. Does a higher metal oxidation state necessarily imply higher reactivity toward H-atom transfer? A computational study of C-H bond oxidation by high-valent iron-oxo and -nitrido complexes. Dalton Trans 2014; 43:6079-86. [PMID: 24492533 DOI: 10.1039/c3dt53051e] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
In this work, the reactions of C-H bond activation by two series of iron-oxo ( (Fe(IV)), (Fe(V)), (Fe(VI))) and -nitrido model complexes ( (Fe(IV)), (Fe(V)), (Fe(VI))) with a nearly identical coordination geometry but varying iron oxidation states ranging from iv to vi were comprehensively investigated using density functional theory. We found that in a distorted octahedral coordination environment, the iron-oxo species and their isoelectronic nitrido analogues feature totally different intrinsic reactivities toward C-H bond cleavage. In the case of the iron-oxo complexes, the reaction barrier monotonically decreases as the iron oxidation state increases, consistent with the gradually enhanced electrophilicity across the series. The iron-nitrido complex is less reactive than its isoelectronic iron-oxo species, and more interestingly, a counterintuitive reactivity pattern was observed, i.e. the activation barriers essentially remain constant independent of the iron oxidation states. The detailed analysis using the Polanyi principle demonstrates that the different reactivities between these two series originate from the distinct thermodynamic driving forces, more specifically, the bond dissociation energies (BDEE-Hs, E = O, N) of the nascent E-H bonds in the FeE-H products. Further decomposition of the BDEE-Hs into the electron and proton affinity components shed light on how the oxidation states modulate the BDEE-Hs of the two series.
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Affiliation(s)
- Caiyun Geng
- Max-Planck Institute for Chemical Energy Conversion, Stiftstr. 34-36, D-45470 Mülheim an der Ruhr, Germany.
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113
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Zapata-Rivera J, Caballol R, Calzado CJ, Liakos DG, Neese F. On the reaction mechanism of the complete intermolecular O2 transfer between mononuclear nickel and manganese complexes with macrocyclic ligands. Chemistry 2014; 20:13296-304. [PMID: 25179780 DOI: 10.1002/chem.201403233] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2014] [Indexed: 11/07/2022]
Abstract
The recently described intermolecular O2 transfer between the side-on Ni-O2 complex [(12-TMC)Ni-O2](+) and the manganese complex [(14-TMC)Mn](2+), where 12-TMC and 14-TMC are 12- and 14-membered macrocyclic ligands, 12-TMC=1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecane and 14-TMC=1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane, is studied by means of DFT methods. B3LYP calculations including long-range corrections and solvent effects are performed to elucidate the mechanism. The potential energy surfaces (PESs) compatible with different electronic states of the reactants have been analyzed. The calculations confirm a two-step reaction, with a first rate-determining bimolecular step and predict the exothermic character of the global process. The relative stability of the products and the reverse barrier are in line with the fact that no reverse reaction is experimentally observed. An intermediate with a μ-η(1):η(1)-O2 coordination and two transition states are identified on the triplet PES, slightly below the corresponding stationary points of the quintet PES, suggesting an intersystem crossing before the first transition state. The calculated activation parameters and the relative energies of the two transition sates and the products are in very good agreement with the experimental data. The calculations suggest that a superoxide anion is transferred during the reaction.
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Affiliation(s)
- Jhon Zapata-Rivera
- Departament de Química Física i Inorgànica, Universitat Rovira i Virgili, Marcel⋅lí Domingo, s/n, 43007 Tarragona (Spain); Present address: Facultad de Ingeniería, Corporación Universidad de la Costa, Calle 58 # 55-66, Barranquilla (Colombia)
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114
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Ray K, Pfaff FF, Wang B, Nam W. Status of Reactive Non-Heme Metal–Oxygen Intermediates in Chemical and Enzymatic Reactions. J Am Chem Soc 2014; 136:13942-58. [DOI: 10.1021/ja507807v] [Citation(s) in RCA: 351] [Impact Index Per Article: 35.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Affiliation(s)
- Kallol Ray
- Department
of Chemistry, Humboldt-Universität zu Berlin, 12489 Berlin, Germany
| | - Florian Felix Pfaff
- Department
of Chemistry, Humboldt-Universität zu Berlin, 12489 Berlin, Germany
| | - Bin Wang
- Department
of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750, Korea
| | - Wonwoo Nam
- Department
of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750, Korea
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115
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Rana S, Bag S, Patra T, Maiti D. Catalytic Electrophilic Halogenations and Haloalkoxylations by Non-Heme Iron Halides. Adv Synth Catal 2014. [DOI: 10.1002/adsc.201400316] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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116
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Abiotic methanogenesis from organosulphur compounds under ambient conditions. Nat Commun 2014; 5:4205. [PMID: 24957135 DOI: 10.1038/ncomms5205] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2014] [Accepted: 05/23/2014] [Indexed: 11/08/2022] Open
Abstract
Methane in the environment is produced by both biotic and abiotic processes. Biomethanation involves the formation of methane by microbes that live in oxygen-free environments. Abiotic methane formation proceeds under conditions at elevated temperature and/or pressure. Here we present a chemical reaction that readily forms methane from organosulphur compounds under highly oxidative conditions at ambient atmospheric pressure and temperature. When using iron(II/III), hydrogen peroxide and ascorbic acid as reagents, S-methyl groups of organosulphur compounds are efficiently converted into methane. In a first step, methyl sulphides are oxidized to the corresponding sulphoxides. In the next step, demethylation of the sulphoxide via homolytic bond cleavage leads to methyl radical formation and finally to methane in high yields. Because sulphoxidation of methyl sulphides is ubiquitous in the environment, this novel chemical route might mimic methane formation in living aerobic organisms.
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117
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Chiang L, Savard D, Shimazaki Y, Thomas F, Storr T. FeIII Bipyrrolidine Phenoxide Complexes and Their Oxidized Analogues. Inorg Chem 2014; 53:5810-9. [DOI: 10.1021/ic500663x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Affiliation(s)
- Linus Chiang
- Department of Chemistry, Simon Fraser University , Burnaby, British Columbia V5A 1S6, Canada
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118
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Nam W, Lee YM, Fukuzumi S. Tuning reactivity and mechanism in oxidation reactions by mononuclear nonheme iron(IV)-oxo complexes. Acc Chem Res 2014; 47:1146-54. [PMID: 24524675 DOI: 10.1021/ar400258p] [Citation(s) in RCA: 383] [Impact Index Per Article: 38.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Mononuclear nonheme iron enzymes generate high-valent iron(IV)-oxo intermediates that effect metabolically important oxidative transformations in the catalytic cycle of dioxygen activation. In 2003, researchers first spectroscopically characterized a mononuclear nonheme iron(IV)-oxo intermediate in the reaction of taurine: α-ketogultarate dioxygenase (TauD). This nonheme iron enzyme with an iron active center was coordinated to a 2-His-1- carboxylate facial triad motif. In the same year, researchers obtained the first crystal structure of a mononuclear nonheme iron(IV)-oxo complex bearing a macrocyclic supporting ligand, [(TMC)Fe(IV)(O)](2+) (TMC = 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecene), in studies that mimicked the biological enzymes. With these breakthrough results, many other studies have examined mononuclear nonheme iron(IV)-oxo intermediates trapped in enzymatic reactions or synthesized in biomimetic reactions. Over the past decade, researchers in the fields of biological, bioinorganic, and oxidation chemistry have extensively investigated the structure, spectroscopy, and reactivity of nonheme iron(IV)-oxo species, leading to a wealth of information from these enzymatic and biomimetic studies. This Account summarizes the reactivity and mechanisms of synthetic mononuclear nonheme iron(IV)-oxo complexes in oxidation reactions and examines factors that modulate their reactivities and change their reaction mechanisms. We focus on several reactions including the oxidation of organic and inorganic compounds, electron transfer, and oxygen atom exchange with water by synthetic mononuclear nonheme iron(IV)-oxo complexes. In addition, we recently observed that the C-H bond activation by nonheme iron(IV)-oxo and other nonheme metal(IV)-oxo complexes does not follow the H-atom abstraction/oxygen-rebound mechanism, which has been well-established in heme systems. The structural and electronic effects of supporting ligands on the oxidizing power of iron(IV)-oxo complexes are significant in these reactions. However, the difference in spin states between nonheme iron(IV)-oxo complexes with an octahedral geometry (with an S = 1 intermediate-spin state) or a trigonal bipyramidal (TBP) geometry (with an S = 2 high-spin state) does not lead to a significant change in reactivity in biomimetic systems. Thus, the importance of the high-spin state of iron(IV)-oxo species in nonheme iron enzymes remains unexplained. We also discuss how the axial and equatorial ligands and binding of redox-inactive metal ions and protons to the iron-oxo moiety influence the reactivities of the nonheme iron(IV)-oxo complexes. We emphasize how these changes can enhance the oxidizing power of nonheme metal(IV)-oxo complexes in oxygen atom transfer and electron-transfer reactions remarkably. This Account demonstrates great advancements in the understanding of the chemistry of mononuclear nonheme iron(IV)-oxo intermediates within the last 10 years.
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Affiliation(s)
- Wonwoo Nam
- Department
of Chemistry and Nano Science, Department of Bioinspired Science,
Center for Biomimetic Systems, Ewha Womans University, Seoul 120-750, Korea
| | - Yong-Min Lee
- Department
of Chemistry and Nano Science, Department of Bioinspired Science,
Center for Biomimetic Systems, Ewha Womans University, Seoul 120-750, Korea
| | - Shunichi Fukuzumi
- Department
of Chemistry and Nano Science, Department of Bioinspired Science,
Center for Biomimetic Systems, Ewha Womans University, Seoul 120-750, Korea
- Department
of Material and Life Science, Graduate School of Engineering, Osaka University, ALCA, Japan Science
and Technology Agency, Suita, Osaka 565-0871, Japan
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Company A, Sabenya G, González-Béjar M, Gómez L, Clémancey M, Blondin G, Jasniewski AJ, Puri M, Browne WR, Latour JM, Que L, Costas M, Pérez-Prieto J, Lloret-Fillol J. Triggering the generation of an iron(IV)-oxo compound and its reactivity toward sulfides by Ru(II) photocatalysis. J Am Chem Soc 2014; 136:4624-33. [PMID: 24568126 PMCID: PMC3985778 DOI: 10.1021/ja412059c] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
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The
preparation of [FeIV(O)(MePy2tacn)]2+ (2, MePy2tacn = N-methyl-N,N-bis(2-picolyl)-1,4,7-triazacyclononane)
by reaction of [FeII(MePy2tacn)(solvent)]2+ (1) and PhIO in CH3CN and its full
characterization are described. This compound can also be prepared
photochemically from its iron(II) precursor by irradiation at 447
nm in the presence of catalytic amounts of [RuII(bpy)3]2+ as photosensitizer and a sacrificial electron
acceptor (Na2S2O8). Remarkably, the
rate of the reaction of the photochemically prepared compound 2 toward sulfides increases 150-fold under irradiation, and 2 is partially regenerated after the sulfide has been consumed;
hence, the process can be repeated several times. The origin of this
rate enhancement has been established by studying the reaction of
chemically generated compound 2 with sulfides under different
conditions, which demonstrated that both light and [RuII(bpy)3]2+ are necessary for the observed increase
in the reaction rate. A combination of nanosecond time-resolved absorption
spectroscopy with laser pulse excitation and other mechanistic studies
has led to the conclusion that an electron transfer mechanism is the
most plausible explanation for the observed rate enhancement. According
to this mechanism, the in-situ-generated [RuIII(bpy)3]3+ oxidizes the sulfide to form the corresponding
radical cation, which is eventually oxidized by 2 to
the corresponding sulfoxide.
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Affiliation(s)
- Anna Company
- Grup de Química Bioinorgànica i Supramolecular (QBIS), Institut de Química Computacional i Catàlisi (IQCC) and Departament de Química, Universitat de Girona, Campus Montilivi , E17071 Girona, Catalonia, Spain
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120
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England J, Bigelow JO, Van Heuvelen KM, Farquhar ER, Martinho M, Meier KK, Frisch JR, Münck E, Que L. An Ultra-Stable Oxoiron(IV) Complex and Its Blue Conjugate Base. Chem Sci 2014; 5:1204-1215. [PMID: 24660055 PMCID: PMC3956701 DOI: 10.1039/c3sc52755g] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Treatment of [FeII(L)](OTf)2 (4), (where L = 1,4,8-Me3cyclam-11-CH2C(O)NMe2) with iodosylbenzene yielded the corresponding S = 1 oxoiron(IV) complex [FeIV(O(L)](OTf)2 (5) in nearly quantitative yield. The remarkably high stability of 5 (t1/2 ≈ 5 days at 25 °C) facilitated its characterization by X-ray crystallography and a raft of spectroscopic techniques. Treatment of 5 with strong base was found to generate a distinct, significantly less stable S = 1 oxoiron(IV) complex, 6 (t1/2 ~ 1.5 hrs. at 0 °C), which could be converted back to 5 by addition of a strong acid; these observations indicate that 5 and 6 represent a conjugate acid-base pair. That 6 can be formulated as [FeIV(O)(L-H)](OTf) was further supported by ESI mass spectrometry, spectroscopic and electrochemical studies, and DFT calculations. The close structural similarity of 5 and 6 provided a unique opportunity to probe the influence of the donor trans to the FeIV=O unit upon its reactivity in H-atom transfer (HAT) and O-atom transfer (OAT), and 5 was found to display greater reactivity than 6 in both OAT and HAT. While the greater OAT reactivity of 5 is expected on the basis of its higher redox potential, its higher HAT reactivity does not follow the anti-electrophilic trend reported for a series of [FeIV(O)(TMC)(X)] complexes (TMC = tetramethylcyclam) and thus appears to be inconsistent with the Two-State Reactivity rationale that is the prevailing explanation for the relative facility of oxoiron(IV) complexes to undergo HAT.
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Affiliation(s)
- Jason England
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant St. SE, Minneapolis, Minnesota 55455, USA
| | - Jennifer O. Bigelow
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant St. SE, Minneapolis, Minnesota 55455, USA
| | - Katherine M. Van Heuvelen
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant St. SE, Minneapolis, Minnesota 55455, USA
| | - Erik R. Farquhar
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant St. SE, Minneapolis, Minnesota 55455, USA
| | - Marléne Martinho
- Department of Chemistry, Carnegie Mellon University, 4400 5Ave., Pittsburgh, PA 15213, USA
| | - Katlyn K. Meier
- Department of Chemistry, Carnegie Mellon University, 4400 5Ave., Pittsburgh, PA 15213, USA
| | - Jonathan R. Frisch
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant St. SE, Minneapolis, Minnesota 55455, USA
| | - Eckard Münck
- Department of Chemistry, Carnegie Mellon University, 4400 5Ave., Pittsburgh, PA 15213, USA
| | - Lawrence Que
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, 207 Pleasant St. SE, Minneapolis, Minnesota 55455, USA
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121
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Ishizuka T, Ohzu S, Kotani H, Shiota Y, Yoshizawa K, Kojima T. Hydrogen atom abstraction reactions independent of C–H bond dissociation energies of organic substrates in water: significance of oxidant–substrate adduct formation. Chem Sci 2014. [DOI: 10.1039/c3sc53002g] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Adduct formation between Ru(iv)–oxo complexes and substrates with hydrogen bonding affords condensed transition states for substrate oxidations in water.
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Affiliation(s)
- Tomoya Ishizuka
- Department of Chemistry
- Graduate School of Pure and Applied Sciences
- University of Tsukuba
- Tsukuba, Japan
| | - Shingo Ohzu
- Department of Chemistry
- Graduate School of Pure and Applied Sciences
- University of Tsukuba
- Tsukuba, Japan
| | - Hiroaki Kotani
- Department of Chemistry
- Graduate School of Pure and Applied Sciences
- University of Tsukuba
- Tsukuba, Japan
| | - Yoshihito Shiota
- Institute for Materials Chemistry and Engineering
- Kyushu University
- Nishi-Ku, Japan
| | - Kazunari Yoshizawa
- Institute for Materials Chemistry and Engineering
- Kyushu University
- Nishi-Ku, Japan
| | - Takahiko Kojima
- Department of Chemistry
- Graduate School of Pure and Applied Sciences
- University of Tsukuba
- Tsukuba, Japan
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122
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Comba P, Wadepohl H, Waleska A. Redox Properties of Iron Complexes with Pentadentate Bispidine Ligands. Aust J Chem 2014. [DOI: 10.1071/ch13454] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The solution coordination chemistry of iron complexes with the pentadentate bispidine ligands L1, L2, and L3 (dimethyl 9-oxo-2,4-di(pyridin-2-yl)-3,7-diazabicyclo[3.3.1]nonane-1,5-dicarboxylate derivatives) was examined. While in acetonitrile, (L1,2)FeII/III species have a preference for Cl– as co-ligand. The corresponding aqua and hydroxido complexes also prevail in the presence of Cl– in aqueous solution. The observed FeII/III potentials in water (cyclic voltammetry) and potentials of (L1–3)FeIV=O (buffered and unbuffered aqueous solutions) are strikingly similar, i.e. the latter are assigned to (L1–3)FeII/III potentials, and published potentials of FeIV=O complexes with other ligands with uncharged amine-pyridine donors, obtained by cyclic voltammetry, have to be considered with caution.
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123
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Comba P, Lee YM, Nam W, Waleska A. Catalytic oxidation of alkanes by iron bispidine complexes and dioxygen: oxygen activation versus autoxidation. Chem Commun (Camb) 2014; 50:412-4. [DOI: 10.1039/c3cc47013j] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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124
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Adams AM, Du Bois J. Organocatalytic C–H hydroxylation with Oxone®enabled by an aqueous fluoroalcohol solvent system. Chem Sci 2014. [DOI: 10.1039/c3sc52649f] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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125
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Que L. High-Valent Nonheme Iron Oxidants in Biology: Lessons from Synthetic Fe IV=O Complexes. BULLETIN OF JAPAN SOCIETY OF COORDINATION CHEMISTRY 2013; 62:30-37. [PMID: 25678937 PMCID: PMC4322783] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Affiliation(s)
- Lawrence Que
- Department of Chemistry and Center for Metals in Biocatalysis, University of Minnesota, Minneapolis, Minnesota, United States
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126
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Hitomi Y, Arakawa K, Kodera M. Electronic Tuning of Iron-Oxo-Mediated CH Activation: Effect of Electron-Donating Ligand on Selectivity. Chemistry 2013; 19:14697-701. [DOI: 10.1002/chem.201302111] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2013] [Indexed: 11/11/2022]
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127
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Lenze M, Sedinkin SL, Bauer EB. Polydentate pyridyl ligands and the catalytic activity of their iron(II) complexes in oxidation reactions utilizing peroxides as the oxidants. ACTA ACUST UNITED AC 2013. [DOI: 10.1016/j.molcata.2013.03.006] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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128
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Tordin E, List M, Monkowius U, Schindler S, Knör G. Synthesis and characterisation of cobalt, nickel and copper complexes with tripodal 4N ligands as novel catalysts for the homogeneous partial oxidation of alkanes. Inorganica Chim Acta 2013; 402:90-96. [PMID: 23805005 PMCID: PMC3688535 DOI: 10.1016/j.ica.2013.03.034] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2013] [Revised: 03/19/2013] [Accepted: 03/20/2013] [Indexed: 11/25/2022]
Abstract
Four new compounds of the general formula [M(L)(CH3COO)][PF6], where L is a tetradentate tripodal ligand such as tris[2-(dimethylamino)ethyl]amine (L1) or (2-aminoethyl)bis(2-pyridylmethyl)amine (L2) and M is Co(II), Ni(II) or Cu(II), have been prepared employing a simple two-step synthesis. The compounds have been characterised by elemental analysis, mass spectroscopy, IR spectroscopy and X-ray diffraction. The catalytic properties of the derivatives containing the aliphatic ligand L1 have been investigated in particular toward the oxidation of cyclohexane and adamantane in the presence of the sacrificial oxidant m-CPBA (meta-chloroperbenzoic acid). Good TONs and selectivity have been determined for the cobalt and nickel compounds.
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Affiliation(s)
- Elisa Tordin
- Institut für Anorganische Chemie, Johannes Kepler Universität Linz (JKU), Altenbergerstr. 69, A-4040 Linz, Austria
| | - Manuela List
- Institut für Chemische Technologie Organischer Stoffe, Johannes Kepler Universität Linz (JKU), Altenbergerstr. 69, A-4040 Linz, Austria
| | - Uwe Monkowius
- Institut für Anorganische Chemie, Johannes Kepler Universität Linz (JKU), Altenbergerstr. 69, A-4040 Linz, Austria
| | - Siegfried Schindler
- Institut für Anorganische und Analytische Chemie, Justus-Liebig-Universität Gieβen, Heinrich-Buff-Ring 58, 35392 Gieβen, Germany
| | - Günther Knör
- Institut für Anorganische Chemie, Johannes Kepler Universität Linz (JKU), Altenbergerstr. 69, A-4040 Linz, Austria
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129
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Comba P, Morgen M, Wadepohl H. Tuning of the Properties of Transition-Metal Bispidine Complexes by Variation of the Basicity of the Aromatic Donor Groups. Inorg Chem 2013; 52:6481-501. [DOI: 10.1021/ic4004214] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Peter Comba
- Anorganisch-Chemisches Institut, Universität Heidelberg, INF 270, D-69120 Heidelberg, Germany
| | - Michael Morgen
- Anorganisch-Chemisches Institut, Universität Heidelberg, INF 270, D-69120 Heidelberg, Germany
| | - Hubert Wadepohl
- Anorganisch-Chemisches Institut, Universität Heidelberg, INF 270, D-69120 Heidelberg, Germany
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130
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Prat I, Company A, Postils V, Ribas X, Que L, Luis JM, Costas M. The mechanism of stereospecific C-H oxidation by Fe(Pytacn) complexes: bioinspired non-heme iron catalysts containing cis-labile exchangeable sites. Chemistry 2013; 19:6724-38. [PMID: 23536410 DOI: 10.1002/chem.201300110] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2013] [Indexed: 11/08/2022]
Abstract
A detailed mechanistic study of the hydroxylation of alkane C-H bonds using H2O2 by a family of mononuclear non heme iron catalysts with the formula [Fe(II)(CF3SO3)2(L)] is described, in which L is a tetradentate ligand containing a triazacyclononane tripod and a pyridine ring bearing different substituents at the α and γ positions, which tune the electronic or steric properties of the corresponding iron complexes. Two inequivalent cis-labile exchangeable sites, occupied by triflate ions, complete the octahedral iron coordination sphere. The C-H hydroxylation mediated by this family of complexes takes place with retention of configuration. Oxygen atoms from water are incorporated into hydroxylated products and the extent of this incorporation depends in a systematic manner on the nature of the catalyst, and the substrate. Mechanistic probes and isotopic analyses, in combination with detailed density functional theory (DFT) calculations, provide strong evidence that C-H hydroxylation is performed by highly electrophilic [Fe(V)(O)(OH)L] species through a concerted asynchronous mechanism, involving homolytic breakage of the C-H bond, followed by rebound of the hydroxyl ligand. The [Fe(V)(O)(OH)L] species can exist in two tautomeric forms, differing in the position of oxo and hydroxide ligands. Isotopic-labeling analysis shows that the relative reactivities of the two tautomeric forms are sensitively affected by the α substituent of the pyridine, and this reactivity behavior is rationalized by computational methods.
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Affiliation(s)
- Irene Prat
- Institut de Química Computacional i Catàlisi (IQCC), Departament de Química, Universitat de Girona, Campus Montilivi, 17071 Girona, Spain
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131
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Hong S, So H, Yoon H, Cho KB, Lee YM, Fukuzumi S, Nam W. Reactivity comparison of high-valent iron(iv)-oxo complexes bearing N-tetramethylated cyclam ligands with different ring size. Dalton Trans 2013; 42:7842-5. [DOI: 10.1039/c3dt50750e] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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132
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Oloo WN, Feng Y, Iyer S, Parmelee S, Xue G, Que L. Cyclohexene as a substrate probe for the nature of the high-valent iron-oxo oxidant in Fe(TPA)-catalyzed oxidations. NEW J CHEM 2013. [DOI: 10.1039/c3nj00524k] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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