1
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Bennett MT, Park KA, Musgrave CB, Brubaker JW, Dickie DA, Goddard WA, Gunnoe TB. Hexa-Fe(III) Carboxylate Complexes Facilitate Aerobic Hydrocarbon Oxidative Functionalization: Rh Catalyzed Oxidative Coupling of Benzene and Ethylene to Form Styrene. ACS Catal 2024; 14:10295-10316. [PMID: 38988649 PMCID: PMC11232027 DOI: 10.1021/acscatal.4c02355] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2024] [Revised: 06/04/2024] [Accepted: 06/05/2024] [Indexed: 07/12/2024]
Abstract
Fe(II) carboxylates react with dioxygen and carboxylic acid to form Fe6(μ-OH)2(μ3-O)2(μ-X)12(HX)2 (X = acetate or pivalate), which is an active oxidant for Rh-catalyzed arene alkenylation. Heating (150-200 °C) the catalyst precursor [(η2-C2H4)2Rh(μ-OAc)]2 with ethylene, benzene, Fe(II) carboxylate, and dioxygen yields styrene >30-fold faster than the reaction with dioxygen in the absence of the Fe(II) carboxylate additive. It is also demonstrated that Fe6(μ-OH)2(μ3-O)2(μ-X)12(HX)2 is an active oxidant under anaerobic conditions, and the reduced material can be reoxidized to Fe6(μ-OH)2(μ3-O)2(μ-X)12(HX)2 by dioxygen. At optimized conditions, a turnover frequency of ∼0.2 s-1 is achieved. Unlike analogous reactions with Cu(II) carboxylate oxidants, which undergo stoichiometric Cu(II)-mediated production of phenyl esters (e.g., phenyl acetate) as side products at temperatures ≥150 °C, no phenyl ester side product is observed when Fe carboxylate additives are used. Kinetic isotope effect experiments using C6H6 and C6D6 give k H/k D = 3.5(3), while the use of protio or monodeutero pivalic acid reveals a small KIE with k H/k D = 1.19(2). First-order dependencies on Fe(II) carboxylate and dioxygen concentration are observed in addition to complicated kinetic dependencies on the concentration of carboxylic acid and ethylene, both of which inhibit the reaction rate at a high concentration. Mechanistic studies are consistent with irreversible benzene C-H activation, ethylene insertion into the formed Rh-Ph bond, β-hydride elimination, and reaction of Rh-H with Fe6(μ-OH)2(μ3-O)2(μ-X)12(HX)2 to regenerate a Rh-carboxylate complex.
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Affiliation(s)
- Marc T. Bennett
- Department
of Chemistry, University of Virginia, Charlottesville, Virginia 22904, United States
| | - Kwanwoo A. Park
- Department
of Chemistry, University of Virginia, Charlottesville, Virginia 22904, United States
| | - Charles B. Musgrave
- Materials
and Process Simulation Center, California
Institute of Technology, Pasadena, California 91125, United States
| | - Jack W. Brubaker
- Materials
and Process Simulation Center, California
Institute of Technology, Pasadena, California 91125, United States
| | - Diane A. Dickie
- Materials
and Process Simulation Center, California
Institute of Technology, Pasadena, California 91125, United States
| | - William A. Goddard
- Materials
and Process Simulation Center, California
Institute of Technology, Pasadena, California 91125, United States
| | - T. Brent Gunnoe
- Department
of Chemistry, University of Virginia, Charlottesville, Virginia 22904, United States
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2
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Daya VP, Jagan R, Chand DK. Self-assembled discrete and polymeric cobalt(II) complexes of a carboxylate appended tripodal tetradentate ligand: reactivity with aerial dioxygen or aqueous hydrogen peroxide. J CHEM SCI 2022. [DOI: 10.1007/s12039-022-02049-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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3
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Suktanarak P, Leeladee P, Tuntulani T. Oxidative ligand cleavage in a copper(
II
) complex containing aniline moiety induced by copper(
II
) perchlorate in acetonitrile. B KOREAN CHEM SOC 2022. [DOI: 10.1002/bkcs.12522] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Pattira Suktanarak
- Faculty of Sport and Health Sciences Thailand National Sports University Lampang Campus Lampang Thailand
| | - Pannee Leeladee
- Department of Chemistry Faculty of Science, Chulalongkorn University Bangkok Thailand
| | - Thawatchai Tuntulani
- Department of Chemistry Faculty of Science, Chulalongkorn University Bangkok Thailand
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4
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Chen J, Klein Gebbink RJM. Deuterated N2Py2 Ligands: Building More Robust Non-Heme Iron Oxidation Catalysts. ACS Catal 2019. [DOI: 10.1021/acscatal.8b04463] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Jianming Chen
- Organic Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University, Universiteitsweg 99, 3584 CG Utrecht, The Netherlands
| | - Robertus J. M. Klein Gebbink
- Organic Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University, Universiteitsweg 99, 3584 CG Utrecht, The Netherlands
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5
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Abstract
The atomistic change of C( sp3)-H to C( sp3)-O can have a profound impact on the physical and biological properties of small molecules. Traditionally, chemical synthesis has relied on pre-existing functionality to install new functionality, and directed approaches to C-H oxidation are an extension of this logic. The impact of developing undirected C-H oxidation reactions with controlled site-selectivity is that scientists gain the ability to diversify complex structures at sites remote from existing functionality, without having to carry out individual de novo syntheses. This Perspective offers a historical view of why, as recently as 2007, it was thought that the differences between aliphatic C-H bonds of the same bond type (for example, 2° aliphatic) were not large enough to distinguish them preparatively with small-molecule catalysis in the absence of directing groups or molecular recognition elements. We give an account of the discovery of Fe(PDP)-catalyzed non-directed aliphatic C-H hydroxylations and how the electronic, steric, and stereoelectronic rules for predicting site-selectivity that emerged have affected a shift in how the chemical community views the reactivity among these bonds. The discovery that site-selectivity could be altered by tuning the catalyst [i.e., Fe(CF3-PDP)] with no changes to the substrate or reaction now gives scientists the ability to exert control on the site of oxidation on a range of functionally and topologically diverse compounds. Collectively, these findings have made possible the emerging area of late-stage C-H functionalizations for streamlining synthesis and derivatizing complex molecules.
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Affiliation(s)
- M. Christina White
- Roger Adams Laboratory, Department of Chemistry, University of Illinois
at Urbana—Champaign, Urbana, Illinois 61801, United States
| | - Jinpeng Zhao
- Roger Adams Laboratory, Department of Chemistry, University of Illinois
at Urbana—Champaign, Urbana, Illinois 61801, United States
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6
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Park H, Ahn HM, Jeong HY, Kim C, Lee D. Non-Heme Iron Catalysts for Olefin Epoxidation: Conformationally Rigid Aryl-Aryl Junction To Support Amine/Imine Multidentate Ligands. Chemistry 2018; 24:8632-8638. [DOI: 10.1002/chem.201800447] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2018] [Indexed: 12/31/2022]
Affiliation(s)
- Hyunchang Park
- Department of Chemistry; Seoul National University; 1 Gwanak-ro Gwanak-gu Seoul 08826 Korea
| | - Hye Mi Ahn
- Department of Fine Chemistry; Seoul National University of Science and Technology; 232 Gongneung-ro Nowon-gu Seoul 01811 Korea
| | - Ha Young Jeong
- Department of Fine Chemistry; Seoul National University of Science and Technology; 232 Gongneung-ro Nowon-gu Seoul 01811 Korea
| | - Cheal Kim
- Department of Fine Chemistry; Seoul National University of Science and Technology; 232 Gongneung-ro Nowon-gu Seoul 01811 Korea
| | - Dongwhan Lee
- Department of Chemistry; Seoul National University; 1 Gwanak-ro Gwanak-gu Seoul 08826 Korea
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7
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Wang VCC, Maji S, Chen PPY, Lee HK, Yu SSF, Chan SI. Alkane Oxidation: Methane Monooxygenases, Related Enzymes, and Their Biomimetics. Chem Rev 2017; 117:8574-8621. [PMID: 28206744 DOI: 10.1021/acs.chemrev.6b00624] [Citation(s) in RCA: 249] [Impact Index Per Article: 35.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Methane monooxygenases (MMOs) mediate the facile conversion of methane into methanol in methanotrophic bacteria with high efficiency under ambient conditions. Because the selective oxidation of methane is extremely challenging, there is considerable interest in understanding how these enzymes carry out this difficult chemistry. The impetus of these efforts is to learn from the microbes to develop a biomimetic catalyst to accomplish the same chemical transformation. Here, we review the progress made over the past two to three decades toward delineating the structures and functions of the catalytic sites in two MMOs: soluble methane monooxygenase (sMMO) and particulate methane monooxygenase (pMMO). sMMO is a water-soluble three-component protein complex consisting of a hydroxylase with a nonheme diiron catalytic site; pMMO is a membrane-bound metalloenzyme with a unique tricopper cluster as the site of hydroxylation. The metal cluster in each of these MMOs harnesses O2 to functionalize the C-H bond using different chemistry. We highlight some of the common basic principles that they share. Finally, the development of functional models of the catalytic sites of MMOs is described. These efforts have culminated in the first successful biomimetic catalyst capable of efficient methane oxidation without overoxidation at room temperature.
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Affiliation(s)
- Vincent C-C Wang
- Institute of Chemistry, Academia Sinica , 128, Section 2, Academia Road, Nankang, Taipei 11529, Taiwan
| | - Suman Maji
- School of Chemical Engineering and Physical Sciences, Lovely Professional University , Jalandhar-Delhi G. T. Road (NH-1), Phagwara, Punjab India 144411
| | - Peter P-Y Chen
- Department of Chemistry, National Chung Hsing University , 250 Kuo Kuang Road, Taichung 402, Taiwan
| | - Hung Kay Lee
- Department of Chemistry, The Chinese University of Hong Kong , Shatin, New Territories, Hong Kong
| | - Steve S-F Yu
- Institute of Chemistry, Academia Sinica , 128, Section 2, Academia Road, Nankang, Taipei 11529, Taiwan
| | - Sunney I Chan
- Institute of Chemistry, Academia Sinica , 128, Section 2, Academia Road, Nankang, Taipei 11529, Taiwan.,Department of Chemistry, National Taiwan University , No. 1, Section 4, Roosevelt Road, Taipei 10617, Taiwan.,Noyes Laboratory, 127-72, California Institute of Technology , 1200 East California Boulevard, Pasadena, California 91125, United States
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8
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Gandomkar S, Fischereder EM, Schrittwieser JH, Wallner S, Habibi Z, Macheroux P, Kroutil W. Enantioselective Oxidative Aerobic Dealkylation of N-Ethyl Benzylisoquinolines by Employing the Berberine Bridge Enzyme. Angew Chem Int Ed Engl 2015; 54:15051-4. [PMID: 26487450 DOI: 10.1002/anie.201507970] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2015] [Indexed: 12/24/2022]
Abstract
N-Dealkylation methods are well described for organic chemistry and the reaction is known in nature and drug metabolism; however, to our knowledge, enantioselective N-dealkylation has not been yet reported. In this study, exclusively the (S)-enantiomers of racemic N-ethyl tertiary amines (1-benzyl-N-ethyl-1,2,3,4-tetrahydroisoquinolines) were dealkylated to give the corresponding secondary (S)-amines in an enantioselective fashion at the expense of molecular oxygen. The reaction is catalyzed by the berberine bridge enzyme, which is known for CC bond formation. The dealkylation was demonstrated on a 100 mg scale and gave optically pure dealkylated products (ee>99 %).
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Affiliation(s)
- Somayyeh Gandomkar
- Institut für Chemie, Organische & Bioorganische Chemie, Universität Graz, NAWI Graz, Heinrichstraße 28, 8010 Graz (Austria).,Department of Pure Chemistry, Faculty of Chemistry, Shahid Beheshti University, G.C. District 1, Evin, Daneshjou Blvd, Tehran (Iran)
| | - Eva-Maria Fischereder
- Institut für Chemie, Organische & Bioorganische Chemie, Universität Graz, NAWI Graz, Heinrichstraße 28, 8010 Graz (Austria)
| | - Joerg H Schrittwieser
- Institut für Chemie, Organische & Bioorganische Chemie, Universität Graz, NAWI Graz, Heinrichstraße 28, 8010 Graz (Austria)
| | - Silvia Wallner
- Institut für Biochemie, Technische Universität Graz, Petersgasse 12, 8010 Graz (Austria)
| | - Zohreh Habibi
- Department of Pure Chemistry, Faculty of Chemistry, Shahid Beheshti University, G.C. District 1, Evin, Daneshjou Blvd, Tehran (Iran)
| | - Peter Macheroux
- Institut für Biochemie, Technische Universität Graz, Petersgasse 12, 8010 Graz (Austria)
| | - Wolfgang Kroutil
- Institut für Chemie, Organische & Bioorganische Chemie, Universität Graz, NAWI Graz, Heinrichstraße 28, 8010 Graz (Austria)
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9
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Gandomkar S, Fischereder EM, Schrittwieser JH, Wallner S, Habibi Z, Macheroux P, Kroutil W. Enantioselektive oxidative aerobe Desalkylierung vonN-Ethylbenzyl- isochinolinen mithilfe des Berberin-Brücken-Enzyms. Angew Chem Int Ed Engl 2015. [DOI: 10.1002/ange.201507970] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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10
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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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11
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Grau M, Kyriacou A, Cabedo Martinez F, de Wispelaere IM, White AJP, Britovsek GJP. Unraveling the origins of catalyst degradation in non-heme iron-based alkane oxidation. Dalton Trans 2014; 43:17108-19. [DOI: 10.1039/c4dt02067g] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A series of iron(ii) complexes with tetradentate and pentadentate pyridyl amine ligands has been used for the oxidation of cyclohexane with hydrogen peroxide. Ligand degradation is observed under oxidising conditions via oxidative N-dealkylation.
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Affiliation(s)
- Michaela Grau
- Department of Chemistry
- Imperial College London
- London, UK
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12
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Coggins MK, Toledo S, Kovacs JA. Isolation and characterization of a dihydroxo-bridged iron(III,III)(μ-OH)2 diamond core derived from dioxygen. Inorg Chem 2013; 52:13325-31. [PMID: 24229319 PMCID: PMC3885352 DOI: 10.1021/ic4010906] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Dioxygen addition to coordinatively unsaturated [Fe(II)(O(Me2)N4(6-Me-DPEN))](PF6) (1) is shown to afford a complex containing a dihydroxo-bridged Fe(III)2(μ-OH)2 diamond core, [Fe(III)(O(Me2)N4(6-Me-DPEN))]2(μ-OH)2(PF6)2·(CH3CH2CN)2 (2). The diamond core of 2 resembles the oxidized methane monooxygenase (MMOox) resting state, as well as the active site product formed following H-atom abstraction from Tyr-OH by ribonucleotide reductase (RNR). The Fe-OH bond lengths of 2 are comparable with those of the MMOHox suggesting that MMOHox contains a Fe(III)2(μ-OH)2 as opposed to Fe(III)2(μ-OH)(μ-OH2) diamond core as had been suggested. Isotopic labeling experiments with (18)O2 and CD3CN indicate that the oxygen and proton of the μ-OH bridges of 2 are derived from dioxygen and acetonitrile. Deuterium incorporation (from CD3CN) suggests that an unobserved intermediate capable of abstracting a H-atom from CH3CN forms en route to 2. Given the high C-H bond dissociation energy (BDE = 97 kcal/mol) of acetonitrile, this indicates that this intermediate is a potent oxidant, possibly a high-valent iron oxo. Consistent with this, iodosylbenzene (PhIO) also reacts with 1 in CD3CN to afford the deuterated Fe(III)2(μ-OD)2 derivative of 2. Intermediates are not spectroscopically observed in either reaction (O2 and PhIO) even at low-temperatures (-80 °C), indicating that this intermediate has a very short lifetime, likely due to its highly reactive nature. Hydroxo-bridged 2 was found to stoichiometrically abstract hydrogen atoms from 9,10-dihydroanthracene (C-H BDE = 76 kcal/mol) at ambient temperatures.
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Affiliation(s)
| | | | - Julie A. Kovacs
- The Department of Chemistry, University of Washington: Box 351700 Seattle, WA 98195-1700
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13
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Kalutharage N, Yi CS. Deaminative and Decarboxylative Catalytic Alkylation of Amino Acids with Ketones. Angew Chem Int Ed Engl 2013; 52:13651-5. [DOI: 10.1002/anie.201307766] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2013] [Indexed: 11/09/2022]
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14
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Kalutharage N, Yi CS. Deaminative and Decarboxylative Catalytic Alkylation of Amino Acids with Ketones. Angew Chem Int Ed Engl 2013. [DOI: 10.1002/ange.201307766] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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15
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16
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Dharmalingam S, Jeon Y, Yoon S. Bis(4,4′′-difluoro-1,1′:3′,1′′-terphenyl-2′-carboxylato-κ O)bis(3,5-dimethyl-1 H-pyrazole-κ N2)manganese(II). Acta Crystallogr Sect E Struct Rep Online 2012; 68:m582-3. [PMID: 22590094 PMCID: PMC3344328 DOI: 10.1107/s1600536812014201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2012] [Accepted: 04/02/2012] [Indexed: 11/16/2022]
Abstract
In the title compound, [Mn(C19H11F2O2)2(C5H8N2)2], the Mn2+ cation is coordinated by the N atoms of two 3,5-dimethylpyrazole ligands and carboxylate O atoms from two 4,4′′-difluoro-1,1′:3′,1′′-terphenyl-2′-carboxylato ligands, forming an MnN2O2 polyhedron with a slightly distorted tetrahedral coordination geometry. Two intramolecular hydrogen bonds are observed between the carboxylate and pyrazole ligands. The combined influence of the sterically hindered carboxylate ligands and the intramolecular hydrogen-bonding interactions stabilizes the title compound with a low coordination number of four. In the crystal, weak C—H⋯F and C—H⋯O hydrogen bonds are observed.
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17
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Do LH, Lippard SJ. Evolution of strategies to prepare synthetic mimics of carboxylate-bridged diiron protein active sites. J Inorg Biochem 2011; 105:1774-85. [PMID: 22113107 PMCID: PMC3232320 DOI: 10.1016/j.jinorgbio.2011.08.025] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2011] [Revised: 08/08/2011] [Accepted: 08/11/2011] [Indexed: 10/17/2022]
Abstract
We present a comprehensive review of research conducted in our laboratory in pursuit of the long-term goal of reproducing the structures and reactivity of carboxylate-bridged diiron centers used in biology to activate dioxygen for the conversion of hydrocarbons to alcohols and related products. This article describes the evolution of strategies devised to achieve these goals and illustrates the challenges in getting there. Particular emphasis is placed on controlling the geometry and coordination environment of the diiron core, preventing formation of polynuclear iron clusters, maintaining the structural integrity of model complexes during reactions with dioxygen, and tuning the ligand framework to stabilize desired oxygenated diiron species. Studies of the various model systems have improved our understanding of the electronic and physical characteristics of carboxylate-bridged diiron units and their reactivity toward molecular oxygen and organic moieties. The principles and lessons that have emerged from these investigations will guide future efforts to develop more sophisticated diiron protein model complexes.
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Affiliation(s)
- Loi H. Do
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139. U.S.A
| | - Stephen J. Lippard
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139. U.S.A
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18
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Vad MS, Nielsen A, Lennartson A, Bond AD, McGrady JE, McKenzie CJ. Switching on oxygen activation by cobalt complexes of pentadentate ligands. Dalton Trans 2011; 40:10698-707. [DOI: 10.1039/c1dt10594a] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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19
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Friedle S, Reisner E, Lippard SJ. Current challenges of modeling diiron enzyme active sites for dioxygen activation by biomimetic synthetic complexes. Chem Soc Rev 2010; 39:2768-79. [PMID: 20485834 DOI: 10.1039/c003079c] [Citation(s) in RCA: 221] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
This tutorial review describes recent progress in modeling the active sites of carboxylate-rich non-heme diiron enzymes that activate dioxygen to carry out several key reactions in Nature. The chemistry of soluble methane monooxygenase, which catalyzes the selective oxidation of methane to methanol, is of particular interest for (bio)technological applications. Novel synthetic diiron complexes that mimic structural, and, to a lesser extent, functional features of these diiron enzymes are discussed. The chemistry of the enzymes is also briefly summarized. A particular focus of this review is on models that mimic characteristics of the diiron systems that were previously not emphasized, including systems that contain (i) aqua ligands, (ii) different substrates tethered to the ligand framework, (iii) dendrimers attached to carboxylates to mimic the protein environment, (iv) two N-donors in a syn-orientation with respect to the iron-iron vector, and (v) a N-rich ligand environment capable of accessing oxygenated high-valent diiron intermediates.
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Affiliation(s)
- Simone Friedle
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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20
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Friedle S, Lippard SJ. Synthesis, Characterization, and Oxygenation Studies of Carboxylate-Bridged Diiron(II) Complexes with Aromatic Substrates Tethered to Pyridine Ligands and the Formation of a Unique Trinuclear Complex. Eur J Inorg Chem 2009; 2009:5506-5515. [PMID: 20376288 DOI: 10.1002/ejic.200900821] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
In this study, diiron(II) complexes were synthesized as small molecule mimics of the reduced active sites in the hydroxylase components of bacterial multicomponent monooxygenases (BMMs). Tethered aromatic substrates were introduced in the form of 2-phenoxypyridines, incorporating hydroxy and methoxy functionalities into windmill-type diiron(II) compounds [Fe(2)(μ-O(2)CAr(R))(2)-(O(2)CAr(R))(2)(L)(2)] (1-4), where (-)O(2)CAr(R) is a sterically encumbering carboxylate, 2,6-di(4-fluorophenyl)- or 2,6-di(p-tolyl)benzoate (R = 4-FPh or Tol, respectively). The inability of 1-4 to hydroxylate the aromatic substrates was ascertained. Upon reaction with dioxygen, compounds 2 and 3 (L = 2-(m-MeOPhO)Py, 2-(p-MeOPhO)Py, respectively) decompose by a known bimolecular pathway to form mixed-valent diiron(II,III) species at low temperature. Use of 2-(pyridin-2-yloxy)phenol as the ligand L resulted in a doubly-bridged diiron complex (4) and an unprecedented phenoxide-bridged triiron(II) complex (5) under slightly modified reaction conditions.
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Affiliation(s)
- Simone Friedle
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
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Siewert I, Limberg C. Low-Molecular-Weight Analogues of the Soluble Methane Monooxygenase (sMMO): From the Structural Mimicking of Resting States and Intermediates to Functional Models. Chemistry 2009; 15:10316-28. [DOI: 10.1002/chem.200901910] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Mandal PC, Bhattacharyya J, Das S, Mukhopadhyay S, Kirschenbaum LJ. Mechanistic studies on the oxidation of pyruvic acid by an oxo-bridged diiron(III,III) complex in aqueous acidic media. Polyhedron 2009. [DOI: 10.1016/j.poly.2009.07.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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23
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Structures, magnetic and thermal properties of polynuclear complexes built by pyridine-2,6-dicarboxylic acid-based multi-dentate ligand. Inorganica Chim Acta 2009. [DOI: 10.1016/j.ica.2009.05.052] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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24
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Botar B, Ellern A, Kögerler P. Acetate-controlled demetalation in multiiron polyoxometalates: A triiron cluster trapped between β- and γ-Keggin isomers. Dalton Trans 2009:5606-8. [DOI: 10.1039/b905211a] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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25
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Pérez LM, Webster CE, Low AA, Hall MB. Theoretical study of the biologically important dioxo diiron diamond core structures. Theor Chem Acc 2008. [DOI: 10.1007/s00214-008-0438-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Bhattacharyya J, Das S, Mukhopadhyay S. Mechanistic studies on oxidation of l-ascorbic acid by an oxo-bridged diiron complex in aqueous acidic media. Dalton Trans 2007:1214-20. [PMID: 17353953 DOI: 10.1039/b615593f] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
[Fe2(micro-O)(phen)4(H2O)2]4+ (1) (Fig. 1, phen = 1,10-phenanthroline) equilibrates with [Fe2(micro-O)(phen)4(H2O)(OH)]3+ (2) and [Fe2(micro-O)(phen)4(OH)2]2+ (3) in aqueous solution in the presence of excess phen, where no phen-releasing equilibria from 1, 2 and 3 exist. 1 quantitatively oxidizes ascorbic acid (H2A) to dehydroascorbic acid (A) in the pH range 3.00-5.50 in the presence of excess phen, which buffers the reaction within 0.05 pH units and ensures complete formation of end iron product ferroin, [Fe(phen)3]2+. The reactive species are 1, 2 and HA- and the reaction proceeds through an initial 1 : 1 inner-sphere adduct formation between 1 and 2 with HA-, followed by a rate limiting outer-sphere one electron one proton (electroprotic) transfer from a second HA- to the ascorbate-unbound iron(III).
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Nehru K, Seo MS, Kim J, Nam W. Oxidative N-Dealkylation Reactions by Oxoiron(IV) Complexes of Nonheme and Heme Ligands. Inorg Chem 2006; 46:293-8. [PMID: 17198439 DOI: 10.1021/ic0614014] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Nonheme and heme iron monooxygenases participate in oxidative N-dealkylation reactions in nature, and high-valent oxoiron(IV) species have been invoked as active oxidants that effect the oxygenation of organic substrates. The present study describes the first example of the oxidative N-dealkylation of N,N-dialkylamines by synthetic nonheme oxoiron(IV) complexes and the reactivity comparisons of nonheme and heme oxoiron(IV) complexes. Detailed mechanistic studies were performed with various N,N-dialkylaniline substrates such as para-substituted N,N-dimethylanilines, para-chloro-N-ethyl-N-methylaniline, para-chloro-N-cyclopropyl-N-isopropylaniline, and deuteriated N,N-dimethylanilines. The results of a linear free-energy correlation, inter- and intramolecular kinetic isotope effects, and product analysis studied with the mechanistic probes demonstrate that the oxidative N-dealkylation reactions by nonheme and heme oxoiron(IV) complexes occur via an electron transfer-proton transfer (ET-PT) mechanism.
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Affiliation(s)
- Kasi Nehru
- Department of Chemistry, Division of Nano Sciences, and Center for Biomimetic Systems, Ewha Womans University, Seoul 120-750, Korea
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Mukherjee R, Bijayi Dhar B, Banerjee R, Mukhopadhyay S. Kinetics of oxidation of phenylhydrazine by aμ-oxo diiron(III,III) complex in acidic aqueous media. J COORD CHEM 2006. [DOI: 10.1080/00958970500410614] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Affiliation(s)
- Ritam Mukherjee
- a Department of Chemistry , Jadavpur University , Calcutta 700 032, India
| | - Basab Bijayi Dhar
- a Department of Chemistry , Jadavpur University , Calcutta 700 032, India
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Yoon S, Lippard SJ. Mechanistic studies of the oxidative N-dealkylation of a substrate tethered to carboxylate-bridged diiron(II) complexes, [Fe2(mu-O2CAr(Tol))2(O2CAr(Tol))2(N,N-Bn2en)2]. Inorg Chem 2006; 45:5438-46. [PMID: 16813407 PMCID: PMC2587132 DOI: 10.1021/ic060307k] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Carboxylate-bridged diiron(II) centers activate dioxygen for the selective oxidation of hydrocarbon substrates in bacterial multicomponent monooxygenases. Synthetic analogues of these systems exist in which substrate fragments tethered to the diiron(II) core through attachment to an N-donor ligand are oxidized by transient species that arise following the introduction of O2 into the system. The present study describes the results of experiments designed to probe mechanistic details of these oxidative N-dealkylation reactions. A series of diiron(II) complexes with ligands N,N-(4-R-Bn)Bnen, where en is ethylenediamine, Bn is benzyl, and R-Bn is benzyl with a para-directing group R = Cl, F, CH3, t-Bu, or OCH3, were prepared. A Hammett plot of the oxygenation product distributions of these complexes, determined by gas chromatographic analysis, reveals a small positive slope of rho = +0.48. Kinetic isotope effect (KIE(intra)) values for oxygenation of [Fe2(mu-O2CAr(Tol))2(O2CAr(Tol))2(N,N-(C6H5CDH)2en)2] and [Fe2(mu-O2CAr(Tol))2(O2CAr(Tol))2(N,N-(C6H5CD2)(C6H5CH2)en)2] are 1.3(1) and 2.2(2) at 23 degrees C, respectively. The positive slope rho and low KIE(intra) values are consistent with a mechanism involving one-electron transfer from the dangling nitrogen atom in N,N-Bn2en to a transient electrophilic diiron intermediate, followed by proton transfer and rearrangement to eliminate benzaldehyde.
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Affiliation(s)
- Sungho Yoon
- Contribution from the Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Stephen J. Lippard
- Contribution from the Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
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Synthesis, characterization and catalytic property of tetradentate Schiff-base complexes for the epoxidation of styrene. ACTA ACUST UNITED AC 2006. [DOI: 10.1016/j.molcata.2006.01.055] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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31
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Mechanistic Studies on the Oxidation of Hydroquinone by an Oxo-bridged Diiron(III,III) Complex in Weakly Acidic Aqueous Media. TRANSIT METAL CHEM 2006. [DOI: 10.1007/s11243-005-6387-y] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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32
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Carson EC, Lippard SJ. Synthesis and oxidation of carboxylate-bridged diiron(II) complexes with substrates tethered to primary alkyl amine ligands. J Inorg Biochem 2006; 100:1109-17. [PMID: 16439023 DOI: 10.1016/j.jinorgbio.2005.11.019] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2005] [Revised: 10/24/2005] [Accepted: 11/04/2005] [Indexed: 11/27/2022]
Abstract
The synthesis and crystallographic characterization of a series of diiron(II) complexes with sterically hindered terphenyl carboxylate ligands and alkyl amine donors are presented. The compounds [Fe(2)(mu-O(2)CAr(Tol))(4)(L)(2)] (L=NH(2)(CH(2))(2)SBn (1); NH(2)(CH(2))(3)SMe (2); NH(2)(CH(2))(3)CCH (3)), where (-)O(2)CAr(Tol) is 2,6-di(p-tolyl)benzoate, and [Fe(2)(mu-O(2)CAr(Xyl))(2)(O(2)CAr(Xyl))(2)(L)(2)] (L=NH(2)(CH(2))(3)SMe (4); NH(2)(CH(2))(3)CCH (5)), where (-)O(2)CAr(Xyl) is 2,6-di(3,5-dimethylphenyl)benzoate, were prepared as small molecule mimics of the catalytic sites of carboxylate-bridged non-heme diiron enzymes. The compounds with the (-)O(2)CAr(Tol) carboxylate form tetrabridged structures, but those containing the more sterically demanding (-)O(2)CAr(Xyl) ligand have only two bridging ligands. The ancillary nitrogen ligands in these carboxylate-rich complexes incorporate potential substrates for the reactive metal centers. Their oxygenation chemistry was studied by product analysis of the organic fragments following decomposition. Compound 1 reacts with dioxygen to afford PhCHO in approximately 30% yield, attributed to oxidative dealkylation of the pendant benzyl group. Compound 3 decomposes to form Fe(II)Fe(III) and Fe(III)Fe(IV) mixed-valence species by established bimolecular pathways upon exposure to dioxygen at low temperatures. Upon decomposition, the alkyne-substituted amine ligand was recovered quantitatively. When the (-)O(2)CAr(Tol) carboxylate was replaced by the (-)O(2)CAr(Xyl) ligand in 5, different behavior was observed. The six-coordinate iron(III) complex with one bidentate and two monodentate carboxylate ligands, [Fe(O(2)CAr(Xyl))(3)(NH(2)(CH(2))(3)CCH)(2)] (6), was isolated from the reaction mixture following oxidation.
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Affiliation(s)
- Emily C Carson
- Department of Chemistry, Massachusetts Institute of Technology, Room 18-498, Cambridge, MA 02139, USA
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Carson EC, Lippard SJ. Synthesis, characterization, and preliminary oxygenation studies of benzyl- and ethyl-substituted pyridine ligands of carboxylate-rich diiron(II) complexes. Inorg Chem 2006; 45:828-36. [PMID: 16411721 PMCID: PMC2505187 DOI: 10.1021/ic051471v] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In this study benzyl and ethyl groups were appended to pyridine and aniline ancillary ligands in diiron(II) complexes of the type [Fe(2)(mu-O(2)CAr(R))(2)(O(2)CAr(R))(2)(L)(2)], where (-)O(2)CAr(R) is a sterically hindered terphenyl carboxylate, 2,6-di(p-tolyl)- or 2,6-di(p-fluorophenyl)benzoate (R = Tol or 4-FPh, respectively). These crystallographically characterized compounds were prepared as analogues of the diiron(II) center in the hydroxylase component of soluble methane monooxygenase (MMOH). The use of 2-benzylpyridine (2-Bnpy) yielded doubly bridged [Fe(2)(mu-O(2)CAr(Tol))(2)(O(2)CAr(Tol))(2)(2-Bnpy)(2)] (1) and [Fe(2)(mu-O(2)CAr(4)(-)(FPh))(2)(O(2)CAr(4)(-)(FPh))(2)(2-Bnpy)(2)] (4), whereas tetra-bridged [Fe(2)(mu-O(2)CAr(Tol))(4)(4-Bnpy)(2)] (3) resulted when 4-benzylpyridine (4-Bnpy) was employed. Similarly, 2-(4-chlorobenzyl)pyridine (2-(4-ClBn)py) and 2-benzylaniline (2-Bnan) were employed as N-donor ligands to prepare [Fe(2)(mu-O(2)CAr(Tol))(2)(O(2)CAr(Tol))(2)(2-(4-ClBn)py)(2)] (2) and [Fe(2)(mu-O(2)CAr(Tol))(2)(O(2)CAr(Tol))(2)(2-Bnan)(2)] (5). The placement of the substituent on the pyridine ring had no effect on the geometry of the diiron(II) compounds isolated when 2-, 3-, or 4-ethylpyridine (2-, 3-, or 4-Etpy) was introduced as the ancillary nitrogen ligand. The isolated [Fe(2)(mu-O(2)CAr(Tol))(2)(O(2)CAr(Tol))(2)(2-Etpy)] (6), [Fe(2)(mu-O(2)CAr(Tol))(2)(O(2)CAr(Tol))(2)(3-Etpy)] (7), [Fe(2)(mu-O(2)CAr(Tol))(2)(O(2)CAr(Tol))(2)(4-Etpy)] (8), and [Fe(2)(mu-O(2)CAr(4)(-FPh))(2)(O(2)CAr(4)(-)(FPh))(2)(2-Etpy)(2)] (9) complexes all contain doubly bridged metal centers. The oxygenation of compounds 1-9 was studied by GC-MS and NMR analysis of the organic fragments following decomposition of the product complexes. Hydrocarbon fragment oxidation occurred for compounds in which the substrate moiety was in close proximity to the diiron center. The extent of oxidation depended upon the exact makeup of the ligand set.
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Affiliation(s)
- Emily C Carson
- Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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Carson EC, Lippard SJ. Dioxygen-initiated oxidation of heteroatomic substrates incorporated into ancillary pyridine ligands of carboxylate-rich diiron(II) complexes. Inorg Chem 2006; 45:837-48. [PMID: 16411722 PMCID: PMC2505175 DOI: 10.1021/ic051476s] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Progress toward the development of functional models of the carboxylate-bridged diiron active site in soluble methane monooxygenase is described in which potential substrates are introduced as substituents on bound pyridine ligands. Pyridine ligands incorporating a thiol, sulfide, sulfoxide, or phosphine moiety were allowed to react with the preassembled diiron(II) complex [Fe(2)(mu-O(2)CAr(R))(2)(O(2)CAr(R))(2)(THF)(2)], where (-)O(2)CAr(R) is a sterically hindered 2,6-di(p-tolyl)- or 2,6-di(p-fluorophenyl)benzoate (R = Tol or 4-FPh). The resulting diiron(II) complexes were characterized crystallographically. Triply and doubly bridged compounds [Fe(2)(mu-O(2)CAr(Tol))(3)(O(2)CAr(Tol))(2-MeSpy)] (4) and [Fe(2)(mu-O(2)CAr(Tol))(2)(O(2)CAr(Tol))(2)(2-MeS(O)py)(2)] (5) resulted when 2-methylthiopyridine (2-MeSpy) and 2-pyridylmethylsulfoxide (2-MeS(O)py), respectively, were employed. Another triply bridged diiron(II) complex, [Fe(2)(mu-O(2)CAr(4)(-)(FPh))(3)-(O(2)CAr(4)(-)(FPh))(2-Ph(2)Ppy)] (3), was obtained containing 2-diphenylphosphinopyridine (2-Ph(2)Ppy). The use of 2-mercaptopyridine (2-HSpy) produced the mononuclear complex [Fe(O(2)CAr(Tol))(2)(2-HSpy)(2)] (6a). Together with that of previously reported [Fe(2)(mu-O(2)CAr(Tol))(3)(O(2)CAr(Tol))(2-PhSpy)] (2) and [Fe(2)(mu-O(2)CAr(Tol))(3)(O(2)CAr(Tol))(2-Ph(2)Ppy)] (1), the dioxygen reactivity of these iron(II) complexes was investigated. A dioxygen-dependent intermediate (6b) formed upon exposure of 6a to O(2), the electronic structure of which was probed by various spectroscopic methods. Exposure of 4 and 5 to dioxygen revealed both sulfide and sulfoxide oxidation. Oxidation of 3 in CH(2)Cl(2) yields [Fe(2)(mu-OH)(2)(mu-O(2)CAr(4)(-)(FPh))(O(2)CAr(4)(-FPh))(3)(OH(2))(2-Ph(2)P(O)py)] (8), which contains the biologically relevant {Fe(2)(mu-OH)(2)(mu-O(2)CR)}(3+) core. This reaction is sensitive to the choice of carboxylate ligands, however, since the p-tolyl analogue 1 yielded a hexanuclear species, 7, upon oxidation.
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Affiliation(s)
- Emily C. Carson
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Stephen J. Lippard
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
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Hawxwell SM, Brammer L. Solvent hydrolysis leads to an unusual Cu(ii) metal–organic framework. CrystEngComm 2006. [DOI: 10.1039/b603274e] [Citation(s) in RCA: 45] [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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36
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Bhattacharyya J, Mukhopadhyay S. Mechanistic Studies on the Oxidation of Nitrite by aμ-Oxodiiron(III,III) Complex in Aqueous Acidic Media. Helv Chim Acta 2005. [DOI: 10.1002/hlca.200590207] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Lippard SJ. Hydroxylation of C-H bonds at carboxylate-bridged diiron centres. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2005; 363:861-77; discussion 1035-40. [PMID: 15901540 DOI: 10.1098/rsta.2004.1532] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Nature uses carboxylate-bridged diiron centres at the active sites of enzymes that catalyse the selective hydroxylation of hydrocarbons to alcohols. The resting diiron(III) state of the hydroxylase component of soluble methane monooxygenase enzyme is converted by two-electron transfer from an NADH-requiring reductase into the active diiron(II) form, which subsequently reacts with O2 to generate a high-valent diiron(IV) oxo species (Q) that converts CH4 into CH3OH. In this step, C-H bond activation is achieved through a transition state having a linear C...H...O unit involving a bound methyl radical. Kinetic studies of the reaction of Q with substrates CH3X, where X=H, D, CH3, NO2, CN or OH, reveal two classes of reactivity depending upon whether binding to the enzyme or C-H bond activation is rate-limiting. Access of substrates to the carboxylate-bridged diiron active site in the hydroxylase (MMOH) occurs through a series of hydrophobic pockets. In the hydroxylase component of the closely related enzyme toluene/o-xylene monooxygenase (ToMOH), substrates enter through a wide channel in the alpha-subunit of the protein that tracks a course identical to that found in the structurally homologous MMOH. Synthetic models for the carboxylate-bridged diiron centres in MMOH and ToMOH have been prepared that reproduce the stoichiometry and key geometric and physical properties of the reduced and oxidized forms of the proteins. Reactions of the diiron(II) model complexes with dioxygen similarly generate reactive intermediates, including high-valent species capable not only of hydroxylating pendant C-H bonds but also of oxidizing phosphine and sulphide groups.
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Affiliation(s)
- Stephen J Lippard
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
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Burdinski D, Cheng K, Lippard SJ. Synthesis of a constrained ligand comprising carboxylate and amine donor groups via direct 1,8-functionalization of positionally protected fluorene. Tetrahedron 2005. [DOI: 10.1016/j.tet.2004.10.111] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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39
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Yoon S, Kelly AE, Lippard SJ. Di- and tetra-bridged diiron(II) complexes with four terphenyl-derived carboxylates and two water molecules. Polyhedron 2004. [DOI: 10.1016/j.poly.2004.06.019] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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41
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Wei Y, Hou H, Fan Y, Zhu Y. Transition Metal Ion Directed Self-Assembly of Polynuclear Coordination Complexes: Structural Characterization and Magnetic Properties. Eur J Inorg Chem 2004. [DOI: 10.1002/ejic.200400110] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Abstract
Synthetic modeling studies of non-heme iron proteins continue to contribute to our understanding of the mechanism of these proteins. Recently, mononuclear Fe(IV)=O complexes have been prepared and characterized to model the same species that are proposed to be the reactive intermediates in reactions involving mononuclear non-heme iron proteins. Generation of such species for the oxidation of organic substrates has also been demonstrated. Other advances include successful modeling of the structural and functional aspects of diiron non-heme proteins with the use of terphenyl-based carboxylate ligands and the development of several iron-based reagents that catalyze oxidation reactions with the use of various oxidants, including dioxygen.
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Affiliation(s)
- Chuan He
- Department of Chemistry, The University of Chicago, IL 60637, USA.
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Naróg D, Lechowicz U, Pietryga T, Sobkowiak A. Iron(II, III)-catalyzed oxidative N-dealkylation of amines with dioxygen. ACTA ACUST UNITED AC 2004. [DOI: 10.1016/j.molcata.2003.11.018] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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Tshuva EY, Lippard SJ. Synthetic Models for Non-Heme Carboxylate-Bridged Diiron Metalloproteins: Strategies and Tactics. Chem Rev 2004; 104:987-1012. [PMID: 14871147 DOI: 10.1021/cr020622y] [Citation(s) in RCA: 536] [Impact Index Per Article: 26.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Edit Y Tshuva
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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Chapter 6 Biocatalysis by methane monooxygenase and its implications for the petroleum industry. ACTA ACUST UNITED AC 2004. [DOI: 10.1016/s0167-2991(04)80147-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/08/2023]
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46
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Yoo SK, Han JH, Lee SJ, Ryu JY, Kim C, Jin SW, Kim Y, Nam W. Conversion of olefins into trans-diols or trans-diol mono-ethers by using iron porphyrin(III) complex and H2O2. INORG CHEM COMMUN 2003. [DOI: 10.1016/s1387-7003(03)00207-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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47
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Zart MK, Sorrell TN, Powell D, Borovik AS. Development of bio-inspired chelates with hydrogen bond donors: synthesis and structure of monomeric metal acetate complexes with intramolecular hydrogen bonds. Dalton Trans 2003. [DOI: 10.1039/b210794p] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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Cotton FA, Daniels LM, Murillo CA, Timmons DJ, Wilkinson CC. The extraordinary ability of guanidinate derivatives to stabilize higher oxidation numbers in dimetal units by modification of redox potentials: structures of Mo(2)(5+) and Mo(2)(6+) compounds. J Am Chem Soc 2002; 124:9249-56. [PMID: 12149031 DOI: 10.1021/ja0266464] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Full characterization of the first homologous series of dimolybdenum paddlewheel compounds having electronic configurations of the types sigma(2)pi(4)delta(x), x = 2, 1, 0, and Mo-Mo bond orders of 4, 3.5, and 3, respectively, has been accomplished with the guanidinate-type ligand hpp (hpp = the anion of 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine). Essentially quantitative oxidation of Mo(2)(hpp)(4), 1, by CH(2)Cl(2) gives Mo(2)(hpp)(4)Cl, 2. The halide in 2 can be replaced by reaction with TlBF(4) to produce Mo(2)(hpp)(4)(BF(4)), 3. Further oxidation of 2 by AgBF(4) produces Mo(2)(hpp)(4)ClBF(4), 4. The change from bond order 4 (in 1) to 3.5 in Mo(2)(hpp)(4)Cl is accompanied by an increase in the Mo-Mo bond length of 0.061 to 2.1280(4) A. A further increase of 0.044 A in the Mo-Mo distance to 2.172(1) A is observed as the bond order decreases to 3 in 4. At the same time, the Mo-N distances decrease smoothly as the oxidation state of the Mo atoms increases. Electrochemical studies have shown two chemically reversible processes at very negative potentials, E(1)(1/2)= -0.444 V and E(2)(1/2)= -1.271 V versus Ag/AgCl. These correspond to the processes Mo(2)(6+/5+) and Mo(2)(5+/4+), respectively. The latter potential is displaced by over 1.5 V relative to those of the Mo(2)(formamidinate)(4) compounds and the first one has never been observed in such complexes. Thus, in surprising contrast to previously observed behavior of the dimolybdenum unit, when it is surrounded by the very basic guanidinate ligand hpp, there is an extraordinary stabilization of the higher oxidation numbers of the molybdenum atoms.
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Affiliation(s)
- F Albert Cotton
- Laboratory for Molecular Structure and Bonding, Department of Chemistry, Texas A&M University, College Station, Texas 77843-3255, USA.
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