1
|
Ekanger LA, Shah RK, Porowski ME, Ziolkowski Z, Calello A. Spectroscopic, electrochemical, and kinetic trends in Fe(III)-thiolate disproportionation near physiologic pH. J Biol Inorg Chem 2024; 29:291-301. [PMID: 38722396 PMCID: PMC11111527 DOI: 10.1007/s00775-024-02051-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2023] [Accepted: 02/01/2024] [Indexed: 05/24/2024]
Abstract
In addition to its primary oxygen-atom-transfer function, cysteamine dioxygenase (ADO) exhibits a relatively understudied anaerobic disproportionation reaction (ADO-Fe(III)-SR → ADO-Fe(II) + ½ RSSR) with its native substrates. Inspired by ADO disproportionation reactivity, we employ [Fe(tacn)Cl3] (tacn = 1,4,7-triazacyclononane) as a precursor for generating Fe(III)-thiolate model complexes in buffered aqueous media. A series of Fe(III)-thiolate model complexes are generated in situ using aqueous [Fe(tacn)Cl3] and thiol-containing ligands cysteamine, penicillamine, mercaptopropionate, cysteine, cysteine methyl ester, N-acetylcysteine, and N-acetylcysteine methyl ester. We observe trends in UV-Vis and electron paramagnetic resonance (EPR) spectra, disproportionation rate constants, and cathodic peak potentials as a function of thiol ligand. These trends will be useful in rationalizing substrate-dependent Fe(III)-thiolate disproportionation reactions in metalloenzymes.
Collapse
Affiliation(s)
- Levi A Ekanger
- Department of Chemistry, The College of New Jersey, Ewing, NJ, 08628, USA.
| | - Ruhi K Shah
- Department of Chemistry, The College of New Jersey, Ewing, NJ, 08628, USA
| | - Matthew E Porowski
- Department of Chemistry, The College of New Jersey, Ewing, NJ, 08628, USA
| | - Zach Ziolkowski
- Department of Chemistry, The College of New Jersey, Ewing, NJ, 08628, USA
| | - Alana Calello
- Department of Chemistry, The College of New Jersey, Ewing, NJ, 08628, USA
| |
Collapse
|
2
|
Mukherjee G, Velmurugan G, Kerscher M, Kumar Satpathy J, Sastri CV, Comba P. Mechanistic Insights into Amphoteric Reactivity of an Iron-Bispidine Complex. Chemistry 2024; 30:e202303127. [PMID: 37942658 DOI: 10.1002/chem.202303127] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2023] [Revised: 11/08/2023] [Accepted: 11/09/2023] [Indexed: 11/10/2023]
Abstract
The reactivity of FeIII -alkylperoxido complexes has remained a riddle to inorganic chemists owing to their thermal instability and impotency towards organic substrates. These iron-oxygen adducts have been known as sluggish oxidants towards oxidative electrophilic and nucleophilic reactions. Herein, we report the synthesis and spectroscopic characterization of a relatively stable mononuclear high-spin FeIII -alkylperoxido complex supported by an engineered bispidine framework. Against the notion, this FeIII -alkylperoxido complex serves as a rare example of versatile reactivity in both electrophilic and nucleophilic reactions. Detailed mechanistic studies and computational calculations reveal a novel reaction mechanism, where a putative superoxido intermediate orchestrates the amphoteric property of the oxidant. The design of the backbone is pivotal to convey stability and reactivity to alkylperoxido and superoxido intermediates. Contrary to the well-known O-O bond cleavage that generates an FeIV -oxido species, the FeIII -alkylperoxido complex reported here undergoes O-C bond scission to generate a superoxido moiety that is responsible for the amphiphilic reactivity.
Collapse
Affiliation(s)
- Gourab Mukherjee
- Department of Catalysis & Fine Chemicals, CSIR-Indian Institute of Chemical Technology Tarnaka, Hyderabad, 500007, India
| | - Gunasekaran Velmurugan
- Anorganisch-Chemisches Institut and, Interdisciplinary Center for Scientific Computing (IWR), Universität Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany)
| | - Marion Kerscher
- Anorganisch-Chemisches Institut and, Interdisciplinary Center for Scientific Computing (IWR), Universität Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany)
| | - Jagnyesh Kumar Satpathy
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati, Assam, 781039, India
| | - Chivukula V Sastri
- Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati, Assam, 781039, India
| | - Peter Comba
- Anorganisch-Chemisches Institut and, Interdisciplinary Center for Scientific Computing (IWR), Universität Heidelberg, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany)
| |
Collapse
|
3
|
Devi T, Dutta K, Deutscher J, Mebs S, Kuhlmann U, Haumann M, Cula B, Dau H, Hildebrandt P, Ray K. A high-spin alkylperoxo-iron(iii) complex with cis-anionic ligands: implications for the superoxide reductase mechanism. Chem Sci 2024; 15:528-533. [PMID: 38179538 PMCID: PMC10762717 DOI: 10.1039/d3sc05603a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2023] [Accepted: 12/05/2023] [Indexed: 01/06/2024] Open
Abstract
The N3O macrocycle of the 12-TMCO ligand stabilizes a high spin (S = 5/2) [FeIII(12-TMCO)(OOtBu)Cl]+ (3-Cl) species in the reaction of [FeII(12-TMCO)(OTf)2] (1-(OTf)2) with tert-butylhydroperoxide (tBuOOH) in the presence of tetraethylammonium chloride (NEt4Cl) in acetonitrile at -20 °C. In the absence of NEt4Cl the oxo-iron(iv) complex 2 [FeIV(12-TMCO)(O)(CH3CN)]2+ is formed, which can be further converted to 3-Cl by adding NEt4Cl and tBuOOH. The role of the cis-chloride ligand in the stabilization of the FeIII-OOtBu moiety can be extended to other anions including the thiolate ligand relevant to the enzyme superoxide reductase (SOR). The present study underlines the importance of subtle electronic changes and secondary interactions in the stability of the biologically relevant metal-dioxygen intermediates. It also provides some rationale for the dramatically different outcomes of the chemistry of iron(iii)peroxy intermediates formed in the catalytic cycles of SOR (Fe-O cleavage) and cytochrome P450 (O-O bond lysis) in similar N4S coordination environments.
Collapse
Affiliation(s)
- Tarali Devi
- Institut für Chemie, Humboldt-Universitat zu Berlin Brook-Taylor-Straße 2 12489 Berlin Germany
- Department of Inorganic and Physical Chemistry, Indian Institute of Science Bangalore Karnataka-560012 India
| | - Kuheli Dutta
- Institut für Chemie, Humboldt-Universitat zu Berlin Brook-Taylor-Straße 2 12489 Berlin Germany
| | - Jennifer Deutscher
- Institut für Chemie, Humboldt-Universitat zu Berlin Brook-Taylor-Straße 2 12489 Berlin Germany
| | - Stefan Mebs
- Department of Physics, Freie Universität Berlin Arnimallee 14 14195 Berlin Germany
| | - Uwe Kuhlmann
- Institut für Chemie, Technische Universität Berlin Fakultät II, Straße des 17. Juni 135 10623 Berlin Germany
| | - Michael Haumann
- Department of Physics, Freie Universität Berlin Arnimallee 14 14195 Berlin Germany
| | - Beatrice Cula
- Institut für Chemie, Humboldt-Universitat zu Berlin Brook-Taylor-Straße 2 12489 Berlin Germany
| | - Holger Dau
- Department of Physics, Freie Universität Berlin Arnimallee 14 14195 Berlin Germany
| | - Peter Hildebrandt
- Institut für Chemie, Technische Universität Berlin Fakultät II, Straße des 17. Juni 135 10623 Berlin Germany
| | - Kallol Ray
- Institut für Chemie, Humboldt-Universitat zu Berlin Brook-Taylor-Straße 2 12489 Berlin Germany
| |
Collapse
|
4
|
Nguyen RC, Davis I, Dasgupta M, Wang Y, Simon PS, Butryn A, Makita H, Bogacz I, Dornevil K, Aller P, Bhowmick A, Chatterjee R, Kim IS, Zhou T, Mendez D, Paley D, Fuller F, Alonso-Mori R, Batyuk A, Sauter NK, Brewster AS, Orville AM, Yachandra VK, Yano J, Kern JF, Liu A. In Situ Structural Observation of a Substrate- and Peroxide-Bound High-Spin Ferric-Hydroperoxo Intermediate in the P450 Enzyme CYP121. J Am Chem Soc 2023; 145:25120-25133. [PMID: 37939223 PMCID: PMC10799213 DOI: 10.1021/jacs.3c04991] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2023]
Abstract
The P450 enzyme CYP121 from Mycobacterium tuberculosis catalyzes a carbon-carbon (C-C) bond coupling cyclization of the dityrosine substrate containing a diketopiperazine ring, cyclo(l-tyrosine-l-tyrosine) (cYY). An unusual high-spin (S = 5/2) ferric intermediate maximizes its population in less than 5 ms in the rapid freeze-quenching study of CYP121 during the shunt reaction with peracetic acid or hydrogen peroxide in acetic acid solution. We show that this intermediate can also be observed in the crystalline state by EPR spectroscopy. By developing an on-demand-rapid-mixing method for time-resolved serial femtosecond crystallography with X-ray free-electron laser (tr-SFX-XFEL) technology covering the millisecond time domain and without freezing, we structurally monitored the reaction in situ at room temperature. After a 200 ms peracetic acid reaction with the cocrystallized enzyme-substrate microcrystal slurry, a ferric-hydroperoxo intermediate is observed, and its structure is determined at 1.85 Å resolution. The structure shows a hydroperoxyl ligand between the heme and the native substrate, cYY. The oxygen atoms of the hydroperoxo are 2.5 and 3.2 Å from the iron ion. The end-on binding ligand adopts a near-side-on geometry and is weakly associated with the iron ion, causing the unusual high-spin state. This compound 0 intermediate, spectroscopically and structurally observed during the catalytic shunt pathway, reveals a unique binding mode that deviates from the end-on compound 0 intermediates in other heme enzymes. The hydroperoxyl ligand is only 2.9 Å from the bound cYY, suggesting an active oxidant role of the intermediate for direct substrate oxidation in the nonhydroxylation C-C bond coupling chemistry.
Collapse
Affiliation(s)
- Romie C. Nguyen
- Department of Chemistry, University of Texas, San Antonio, TX 78249, United States
| | - Ian Davis
- Department of Chemistry, University of Texas, San Antonio, TX 78249, United States
| | - Medhanjali Dasgupta
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States
| | - Yifan Wang
- Department of Chemistry, University of Texas, San Antonio, TX 78249, United States
| | - Philipp S. Simon
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States
| | - Agata Butryn
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, United Kingdom
- Research Complex at Harwell, Rutherford Appleton Laboratory, Didcot, Oxfordshire OX11 0FA, United Kingdom
| | - Hiroki Makita
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States
| | - Isabel Bogacz
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States
| | - Kednerlin Dornevil
- Department of Chemistry, University of Texas, San Antonio, TX 78249, United States
| | - Pierre Aller
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, United Kingdom
- Research Complex at Harwell, Rutherford Appleton Laboratory, Didcot, Oxfordshire OX11 0FA, United Kingdom
| | - Asmit Bhowmick
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States
| | - Ruchira Chatterjee
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States
| | - In-Sik Kim
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States
| | - Tiankun Zhou
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, United Kingdom
- Research Complex at Harwell, Rutherford Appleton Laboratory, Didcot, Oxfordshire OX11 0FA, United Kingdom
| | - Derek Mendez
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States
| | - Daniel Paley
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States
| | - Franklin Fuller
- LCLS, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, United States
| | - Roberto Alonso-Mori
- LCLS, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, United States
| | - Alexander Batyuk
- LCLS, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, United States
| | - Nicholas K. Sauter
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States
| | - Aaron S. Brewster
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States
| | - Allen M. Orville
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, United Kingdom
- Research Complex at Harwell, Rutherford Appleton Laboratory, Didcot, Oxfordshire OX11 0FA, United Kingdom
| | - Vittal K. Yachandra
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States
| | - Junko Yano
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States
| | - Jan F. Kern
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States
| | - Aimin Liu
- Department of Chemistry, University of Texas, San Antonio, TX 78249, United States
| |
Collapse
|
5
|
Mukherjee G, Satpathy JK, Bagha UK, Mubarak MQE, Sastri CV, de Visser SP. Inspiration from Nature: Influence of Engineered Ligand Scaffolds and Auxiliary Factors on the Reactivity of Biomimetic Oxidants. ACS Catal 2021. [DOI: 10.1021/acscatal.1c01993] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Gourab Mukherjee
- Department of Chemistry, Indian Institute of Technology Guwahati, 781039, Assam, India
| | - Jagnyesh K. Satpathy
- Department of Chemistry, Indian Institute of Technology Guwahati, 781039, Assam, India
| | - Umesh K. Bagha
- Department of Chemistry, Indian Institute of Technology Guwahati, 781039, Assam, India
| | - M. Qadri E. Mubarak
- Manchester Institute of Biotechnology, The University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom
- Fakulti Sains dan Teknologi, Universiti Sains Islam Malaysia, Bandar Baru Nilai, 71800 Nilai, Negeri Sembilan Malaysia
| | - Chivukula V. Sastri
- Department of Chemistry, Indian Institute of Technology Guwahati, 781039, Assam, India
| | - Sam P. de Visser
- Department of Chemistry, Indian Institute of Technology Guwahati, 781039, Assam, India
- Manchester Institute of Biotechnology, The University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom
- Department of Chemical Engineering and Analytical Science, The University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
| |
Collapse
|
6
|
Dedushko MA, Pikul JH, Kovacs JA. Superoxide Oxidation by a Thiolate-Ligated Iron Complex and Anion Inhibition. Inorg Chem 2021; 60:7250-7261. [PMID: 33900756 DOI: 10.1021/acs.inorgchem.1c00336] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Superoxide (O2•-) is a toxic radical, generated via the adventitious reduction of dioxygen (O2), which has been implicated in a number of human disease states. Nonheme iron enzymes, superoxide reductase (SOR) and superoxide dismutase (SOD), detoxify O2•- via reduction to afford H2O2 and disproportionation to afford O2 and H2O2, respectively. The former contains a thiolate in the coordination sphere, which has been proposed to prevent O2•- oxidation to O2. The work described herein shows that, in contrast to this, oxidized thiolate-ligated [FeIII(SMe2N4(tren)(THF)]2+ (1ox-THF) is capable of oxidizing O2•- to O2. Coordinating anions, Cl- and OAc-, are shown to inhibit dioxygen evolution, implicating an inner-sphere mechanism. Previously we showed that the reduced thiolate-ligated [FeII(SMe2N4(tren))]+ (1) is capable of reducing O2•- via a proton-dependent inner-sphere mechanism involving a transient Fe(III)-OOH intermediate. A transient ferric-superoxo intermediate, [FeIII(SMe2N4(tren))(O2)]+ (3), is detected by electronic absorption spectroscopy at -130 °C in the reaction between 1ox-THF and KO2 and shown to evolve O2 upon slight warming to -115 °C. The DFT calculated O-O (1.306 Å) and Fe-O (1.943 Å) bond lengths of 3 are typical of ferric-superoxo complexes, and the time-dependent DFT calculated electronic absorption spectrum of 3 reproduces the experimental spectrum. The electronic structure of 3 is shown to consist of two antiferromagnetically coupled (Jcalc = -180 cm-1) unpaired electrons, one in a superoxo π*(O-O) orbital and the other in an antibonding π*(Fe(dyz)-S(py)) orbital.
Collapse
Affiliation(s)
- Maksym A Dedushko
- The Department of Chemistry, University of Washington: Box 351700, Seattle, Washington 98195-1700, United States
| | - Jessica H Pikul
- The Department of Chemistry, University of Washington: Box 351700, Seattle, Washington 98195-1700, United States
| | - Julie A Kovacs
- The Department of Chemistry, University of Washington: Box 351700, Seattle, Washington 98195-1700, United States
| |
Collapse
|
7
|
Jana RD, Das A, Paine TK. Enhancing Chemo- and Stereoselectivity in C-H Bond Oxygenation with H 2O 2 by Nonheme High-Spin Iron Catalysts: The Role of Lewis Acid and Multimetal Centers. Inorg Chem 2021; 60:5969-5979. [PMID: 33784082 DOI: 10.1021/acs.inorgchem.1c00397] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Spin states of iron often direct the selectivity in oxidation catalysis by iron complexes using hydrogen peroxide (H2O2) on an oxidant. While low-spin iron(III) hydroperoxides display stereoselective C-H bond hydroxylation, the reactions are nonstereoselective with high-spin iron(II) catalysts. The catalytic studies with a series of high-spin iron(II) complexes of N4 ligands with H2O2 and Sc3+ reported here reveal that the Lewis acid promotes catalytic C-H bond hydroxylation with high chemo- and stereoselectivity. This reactivity pattern is observed with iron(II) complexes containing two cis-labile sites. The enhanced selectivity for C-H bond hydroxylation catalyzed by the high-spin iron(II) complexes in the presence of Sc3+ parallels that of the low-spin iron catalysts. Furthermore, the introduction of multimetal centers enhances the activity and selectivity of the iron catalyst. The study provides insights into the development of peroxide-dependent bioinspired catalysts for the selective oxygenation of C-H bonds without the restriction of using iron complexes of strong-field ligands.
Collapse
Affiliation(s)
- Rahul Dev Jana
- School of Chemical Sciences, Indian Association for the Cultivation of Science (IACS), 2A & 2B Raja S. C. Mullick Road, Jadavpur, Kolkata 700032, India
| | - Abhishek Das
- School of Chemical Sciences, Indian Association for the Cultivation of Science (IACS), 2A & 2B Raja S. C. Mullick Road, Jadavpur, Kolkata 700032, India
| | - Tapan Kanti Paine
- School of Chemical Sciences, Indian Association for the Cultivation of Science (IACS), 2A & 2B Raja S. C. Mullick Road, Jadavpur, Kolkata 700032, India
| |
Collapse
|
8
|
Mukherjee G, Sastri CV. Eccentricities in Spectroscopy and Reactivity of Non‐Heme Metal Intermediates Contained in Bispidine Scaffolds. Isr J Chem 2020. [DOI: 10.1002/ijch.202000045] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Gourab Mukherjee
- Department of Chemistry Indian Institute of Technology Guwahati Guwahati, Assam 781039 India
| | - Chivukula V. Sastri
- Department of Chemistry Indian Institute of Technology Guwahati Guwahati, Assam 781039 India
| |
Collapse
|
9
|
Bhattacharya S, Singh R, Paine TK. Effect of Ligand Fields on the Reactivity of O 2 -Activating Iron(II)-Benzilate Complexes of Neutral N5 Donor Ligands. Chem Asian J 2020; 15:1360-1368. [PMID: 32141712 DOI: 10.1002/asia.202000142] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2020] [Revised: 03/04/2020] [Indexed: 01/05/2023]
Abstract
Three new iron(II)-benzilate complexes [(N4Py)FeII (benzilate)]ClO4 (1), [(N4PyMe2 )FeII (benzilate)]ClO4 (2) and [(N4PyMe4 )FeII (benzilate)]ClO4 (3) of neutral pentadentate nitrogen donor ligands have been isolated and characterized to study their dioxygen reactivity. Single-crystal X-ray structures reveal a mononuclear six-coordinate iron(II) center in each case, where benzilate binds to the iron center in monodentate mode via one carboxylate oxygen. Introduction of methyl groups in the 6-positions of the pyridine rings makes the N4PyMe2 and N4PyMe4 ligand fields weaker compared to that of the parent N4Py ligand. All the complexes (1-3) react with dioxygen to decarboxylate the coordinated benzilate to benzophenone quantitatively. The decarboxylation is faster for the complex of the more sterically hindered ligand and follows the order 3>2>1. The complexes display oxygen atom transfer reactivity to thioanisole and also exhibit hydrogen atom transfer reactions with substrates containing weak C-H bonds. Based on interception studies with external substrates, labelling experiments and Hammett analysis, a nucleophilic iron(II)-hydroperoxo species is proposed to form upon two-electron reductive activation of dioxygen by each iron(II)-benzilate complex. The nucleophilic oxidants are converted to the corresponding electrophilic iron(IV)-oxo oxidant upon treatment with a protic acid. The high-spin iron(II)-benzilate complex with the weakest ligand field results in the formation of a more reactive iron-oxygen oxidant.
Collapse
Affiliation(s)
- Shrabanti Bhattacharya
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A&2B Raja S. C. Mullick Road, Jadavpur, Kolkata, 700032, India
| | - Reena Singh
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A&2B Raja S. C. Mullick Road, Jadavpur, Kolkata, 700032, India
| | - Tapan Kanti Paine
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A&2B Raja S. C. Mullick Road, Jadavpur, Kolkata, 700032, India
| |
Collapse
|
10
|
Oh H, Ching WM, Kim J, Lee WZ, Hong S. Hydrogen Bond-Enabled Heterolytic and Homolytic Peroxide Activation within Nonheme Copper(II)-Alkylperoxo Complexes. Inorg Chem 2019; 58:12964-12974. [DOI: 10.1021/acs.inorgchem.9b01898] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Hana Oh
- Department of Chemistry, Sookmyung Women’s University, Seoul 04310, Korea
| | - Wei-Min Ching
- Department of Chemistry, National Taiwan Normal University, Taipei 11677, Taiwan
- Instrumental Center, National Taiwan Normal University, Taipei 11677, Taiwan
| | - Jin Kim
- Western Seoul Centre, Korea Basic Science Institute, Seoul 03759, Republic of Korea
| | - Way-Zen Lee
- Department of Chemistry, National Taiwan Normal University, Taipei 11677, Taiwan
- Department of Medicinal and Applied Chemistry, Kaohsiung Medical University, Kaohsiung 807, Taiwan
| | - Seungwoo Hong
- Department of Chemistry, Sookmyung Women’s University, Seoul 04310, Korea
| |
Collapse
|
11
|
Ghosh I, Banerjee S, Paul S, Corona T, Paine TK. Highly Selective and Catalytic Oxygenations of C-H and C=C Bonds by a Mononuclear Nonheme High-Spin Iron(III)-Alkylperoxo Species. Angew Chem Int Ed Engl 2019; 58:12534-12539. [PMID: 31246329 DOI: 10.1002/anie.201906978] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Indexed: 10/26/2022]
Abstract
The reactivity of a mononuclear high-spin iron(III)-alkylperoxo intermediate [FeIII (t-BuLUrea )(OOCm)(OH2 )]2+ (2), generated from [FeII (t-BuLUrea )(H2 O)(OTf)](OTf) (1) [t-BuLUrea =1,1'-(((pyridin-2-ylmethyl)azanediyl)bis(ethane-2,1-diyl))bis(3-(tert-butyl)urea), OTf=trifluoromethanesulfonate] with cumyl hydroperoxide (CmOOH), toward the C-H and C=C bonds of hydrocarbons is reported. 2 oxygenates the strong C-H bonds of aliphatic substrates with high chemo- and stereoselectivity in the presence of 2,6-lutidine. While 2 itself is a sluggish oxidant, 2,6-lutidine assists the heterolytic O-O bond cleavage of the metal-bound alkylperoxo, giving rise to a reactive metal-based oxidant. The roles of the urea groups on the supporting ligand, and of the base, in directing the selective and catalytic oxygenation of hydrocarbon substrates by 2 are discussed.
Collapse
Affiliation(s)
- Ivy Ghosh
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Jadavpur, Kolkata-, 700032, India
| | - Sridhar Banerjee
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Jadavpur, Kolkata-, 700032, India
| | - Satadal Paul
- Darjeeling Polytechnic, Kurseong, Darjeeling, 734203, India
| | - Teresa Corona
- Humboldt-Universität zu Berlin, Department of Chemistry, Brook-Taylor-Strasse 2, 12489, Berlin, Germany
| | - Tapan Kanti Paine
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Jadavpur, Kolkata-, 700032, India
| |
Collapse
|
12
|
Ghosh I, Banerjee S, Paul S, Corona T, Paine TK. Highly Selective and Catalytic Oxygenations of C−H and C=C Bonds by a Mononuclear Nonheme High‐Spin Iron(III)‐Alkylperoxo Species. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201906978] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Ivy Ghosh
- School of Chemical Sciences, Indian Association for the Cultivation of Science 2A & 2B Raja S. C. Mullick Road Jadavpur, Kolkata- 700032 India
| | - Sridhar Banerjee
- School of Chemical Sciences, Indian Association for the Cultivation of Science 2A & 2B Raja S. C. Mullick Road Jadavpur, Kolkata- 700032 India
| | - Satadal Paul
- Darjeeling Polytechnic Kurseong Darjeeling 734203 India
| | - Teresa Corona
- Humboldt-Universität zu BerlinDepartment of Chemistry Brook-Taylor-Strasse 2 12489 Berlin Germany
| | - Tapan Kanti Paine
- School of Chemical Sciences, Indian Association for the Cultivation of Science 2A & 2B Raja S. C. Mullick Road Jadavpur, Kolkata- 700032 India
| |
Collapse
|
13
|
Wegeberg C, Browne WR, McKenzie CJ. cis Donor Influence on O–O Bond Lability in Iron(III) Hydroperoxo Complexes: Oxidation Catalysis and Ligand Transformation. Inorg Chem 2019; 58:8983-8994. [DOI: 10.1021/acs.inorgchem.9b00247] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Christina Wegeberg
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark
- Molecular Inorganic Chemistry, Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Wesley R. Browne
- Molecular Inorganic Chemistry, Stratingh Institute for Chemistry, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Christine J. McKenzie
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, 5230 Odense M, Denmark
| |
Collapse
|
14
|
Wang L, Gennari M, Cantú Reinhard FG, Gutiérrez J, Morozan A, Philouze C, Demeshko S, Artero V, Meyer F, de Visser SP, Duboc C. A Non-Heme Diiron Complex for (Electro)catalytic Reduction of Dioxygen: Tuning the Selectivity through Electron Delivery. J Am Chem Soc 2019; 141:8244-8253. [DOI: 10.1021/jacs.9b02011] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Affiliation(s)
- Lianke Wang
- Université Grenoble Alpes, CNRS UMR 5250, DCM, F-38000 Grenoble, France
| | - Marcello Gennari
- Université Grenoble Alpes, CNRS UMR 5250, DCM, F-38000 Grenoble, France
| | - Fabián G. Cantú Reinhard
- Manchester Institute of Biotechnology and School of Chemical Engineering and Analytical Science, The University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom
| | - Javier Gutiérrez
- Université Grenoble Alpes, CNRS UMR 5250, DCM, F-38000 Grenoble, France
| | - Adina Morozan
- Université Grenoble Alpes, CNRS, CEA, Laboratoire de Chimie et
Biologie des Métaux, F-38000 Grenoble, France
| | | | - Serhiy Demeshko
- Institut für Anorganische Chemie, Universität Göttingen, Tammannstrasse 4, D-37077 Göttingen, Germany
| | - Vincent Artero
- Université Grenoble Alpes, CNRS, CEA, Laboratoire de Chimie et
Biologie des Métaux, F-38000 Grenoble, France
| | - Franc Meyer
- Institut für Anorganische Chemie, Universität Göttingen, Tammannstrasse 4, D-37077 Göttingen, Germany
| | - Sam P. de Visser
- Manchester Institute of Biotechnology and School of Chemical Engineering and Analytical Science, The University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom
| | - Carole Duboc
- Université Grenoble Alpes, CNRS UMR 5250, DCM, F-38000 Grenoble, France
| |
Collapse
|
15
|
|
16
|
Parham JD, Wijeratne GB, Rice DB, Jackson TA. Spectroscopic and Structural Characterization of Mn(III)-Alkylperoxo Complexes Supported by Pentadentate Amide-Containing Ligands. Inorg Chem 2018; 57:2489-2502. [DOI: 10.1021/acs.inorgchem.7b02793] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Joshua D. Parham
- Department of Chemistry and Center for Environmentally Beneficial Catalysis, University of Kansas, Lawrence, Kansas 66045, United States
| | - Gayan B. Wijeratne
- Department of Chemistry and Center for Environmentally Beneficial Catalysis, University of Kansas, Lawrence, Kansas 66045, United States
| | - Derek B. Rice
- Department of Chemistry and Center for Environmentally Beneficial Catalysis, University of Kansas, Lawrence, Kansas 66045, United States
| | - Timothy A. Jackson
- Department of Chemistry and Center for Environmentally Beneficial Catalysis, University of Kansas, Lawrence, Kansas 66045, United States
| |
Collapse
|
17
|
Geometric effects on O O bond scission of copper(II)-alkylperoxide complexes. J Inorg Biochem 2017; 177:375-383. [DOI: 10.1016/j.jinorgbio.2017.08.016] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2017] [Revised: 08/01/2017] [Accepted: 08/21/2017] [Indexed: 11/20/2022]
|
18
|
Li J, Banerjee A, Hasse TA, Loloee R, Biros SM, Staples RJ, Chavez FA. Synthesis and reactivity of a 4His enzyme model complex. RSC Adv 2017; 7:50713-50719. [PMID: 29147561 PMCID: PMC5683714 DOI: 10.1039/c7ra09456f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
A new iron(II) complex has been prepared and characterized. [Fe(TrIm)4(OTf)2] (1, TrIm = 1-Tritylimidazole). The solid state structure of 1 has been determined by X-ray crystallography. Compound 1 crystallizes in triclinic space group P1̄, with a = 13.342(7) Å, b = 13.5131(7) Å and c = 13.7025(7) Å. The iron center resides in distorted octahedral geometry coordinated to four equatorial imidazole groups and two axial triflate oxygens groups. The complex is high spin between 20 K and 300 K as indicated by variable field variable temperature magnetic measurements. A fit of the magnetic data yielded g = 2.24 and D = -0.80 cm-1. A large HOMO-LUMO gap energy (3.89 eV) exists for 1 indicating high stability. Addition of H2O2 or t BuOOH to 1 results in formation of an oxygenated intermediate which upon decomposition results in oxidation of the trityl substituent on the imidazole ligand.
Collapse
Affiliation(s)
- Jia Li
- Department of Chemistry, Oakland University, Rochester, MI 48309, USA, , Ph: (248) 370-4092
| | - Atanu Banerjee
- Department of Chemistry, Oakland University, Rochester, MI 48309, USA, , Ph: (248) 370-4092
| | - Timothy A Hasse
- Department of Chemistry, Oakland University, Rochester, MI 48309, USA, , Ph: (248) 370-4092
| | - Reza Loloee
- Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824, USA
| | - Shannon M Biros
- Department of Chemistry, Michigan State University, East Lansing, MI 48824, USA
| | - Richard J Staples
- Department of Chemistry, Michigan State University, East Lansing, MI 48824, USA
| | - Ferman A Chavez
- Department of Chemistry, Oakland University, Rochester, MI 48309, USA, , Ph: (248) 370-4092
| |
Collapse
|
19
|
Kim B, Jeong D, Cho J. Nucleophilic reactivity of copper(ii)–alkylperoxo complexes. Chem Commun (Camb) 2017; 53:9328-9331. [DOI: 10.1039/c7cc03965d] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Copper(ii)–alkylperoxo adducts, [Cu(CHDAP)(OOR)]+ (CHDAP = N,N′-dicyclohexyl-2,11-diaza[3,3](2,6)pyridinophane; R = C(CH3)2Ph and tBu), perform aldehyde deformylation (i.e., nucleophilic reactivity) under the stoichiometric reaction conditions.
Collapse
Affiliation(s)
- Bohee Kim
- Department of Emerging Materials Science
- DGIST
- Daegu 42988
- Korea
| | - Donghyun Jeong
- Department of Emerging Materials Science
- DGIST
- Daegu 42988
- Korea
| | - Jaeheung Cho
- Department of Emerging Materials Science
- DGIST
- Daegu 42988
- Korea
| |
Collapse
|
20
|
Villar-Acevedo G, Lugo-Mas P, Blakely MN, Rees JA, Ganas AS, Hanada EM, Kaminsky W, Kovacs JA. Metal-Assisted Oxo Atom Addition to an Fe(III) Thiolate. J Am Chem Soc 2016; 139:119-129. [PMID: 28033001 DOI: 10.1021/jacs.6b03512] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Cysteinate oxygenation is intimately tied to the function of both cysteine dioxygenases (CDOs) and nitrile hydratases (NHases), and yet the mechanisms by which sulfurs are oxidized by these enzymes are unknown, in part because intermediates have yet to be observed. Herein, we report a five-coordinate bis-thiolate ligated Fe(III) complex, [FeIII(S2Me2N3(Pr,Pr))]+ (2), that reacts with oxo atom donors (PhIO, IBX-ester, and H2O2) to afford a rare example of a singly oxygenated sulfenate, [FeIII(η2-SMe2O)(SMe2)N3(Pr,Pr)]+ (5), resembling both a proposed intermediate in the CDO catalytic cycle and the essential NHase Fe-S(O)Cys114 proposed to be intimately involved in nitrile hydrolysis. Comparison of the reactivity of 2 with that of a more electron-rich, crystallographically characterized derivative, [FeIIIS2Me2NMeN2amide(Pr,Pr)]- (8), shows that oxo atom donor reactivity correlates with the metal ion's ability to bind exogenous ligands. Density functional theory calculations suggest that the mechanism of S-oxygenation does not proceed via direct attack at the thiolate sulfurs; the average spin-density on the thiolate sulfurs is approximately the same for 2 and 8, and Mulliken charges on the sulfurs of 8 are roughly twice those of 2, implying that 8 should be more susceptible to sulfur oxidation. Carboxamide-ligated 8 is shown to be unreactive towards oxo atom donors, in contrast to imine-ligated 2. Azide (N3-) is shown to inhibit sulfur oxidation with 2, and a green intermediate is observed, which then slowly converts to sulfenate-ligated 5. This suggests that the mechanism of sulfur oxidation involves initial coordination of the oxo atom donor to the metal ion. Whether the green intermediate is an oxo atom donor adduct, Fe-O═I-Ph, or an Fe(V)═O remains to be determined.
Collapse
Affiliation(s)
- Gloria Villar-Acevedo
- The Department of Chemistry, University of Washington , Box 351700, Seattle, Washington 98195-1700, United States
| | - Priscilla Lugo-Mas
- The Department of Chemistry, University of Washington , Box 351700, Seattle, Washington 98195-1700, United States
| | - Maike N Blakely
- The Department of Chemistry, University of Washington , Box 351700, Seattle, Washington 98195-1700, United States
| | - Julian A Rees
- The Department of Chemistry, University of Washington , Box 351700, Seattle, Washington 98195-1700, United States
| | - Abbie S Ganas
- The Department of Chemistry, University of Washington , Box 351700, Seattle, Washington 98195-1700, United States
| | - Erin M Hanada
- The Department of Chemistry, University of Washington , Box 351700, Seattle, Washington 98195-1700, United States
| | - Werner Kaminsky
- The Department of Chemistry, University of Washington , Box 351700, Seattle, Washington 98195-1700, United States
| | - Julie A Kovacs
- The Department of Chemistry, University of Washington , Box 351700, Seattle, Washington 98195-1700, United States
| |
Collapse
|
21
|
Attia AAA, Cioloboc D, Lupan A, Silaghi-Dumitrescu R. Multiconfigurational and DFT analyses of the electromeric formulation and UV-vis absorption spectra of the superoxide adduct of ferrous superoxide reductase. J Inorg Biochem 2016; 165:49-53. [PMID: 27768962 DOI: 10.1016/j.jinorgbio.2016.09.017] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2016] [Revised: 09/14/2016] [Accepted: 09/29/2016] [Indexed: 11/29/2022]
Abstract
The putative initial adduct of ferrous superoxide reductase (SOR) with superoxide has been alternatively formulated as ferric-peroxo or ferrous-superoxo. The ~600-nm UV-vis absorption band proposed to be assigned to this adduct (either as sole intermediate in the SOR catalytic cycle, or as one of the two intermediates) has recently been interpreted as due to a ligand-to-metal charge transfer, involving thiolate and superoxide in a ferrous complex, contrary to an alternative assignment as a predominantly cysteine thiolate-to-ferric charge transfer in a ferric-peroxo electromer. In an attempt to clarify the electromeric formulation of this adduct, we report a computational study using a multiconfigurational complete active space self-consistent field (MC-CASSCF) wave function approach as well as modelling the UV-vis absorption spectra with time-dependent density functional theory (TD-DFT). The MC-CASSCF calculations disclose a weak interaction between iron and the dioxygenic ligand and a dominant configuration with an essentially ferrous-superoxo character. The computed UV-vis absorption spectra reveal a marked dependence on the choice of density functional - both in terms of location of bands and in terms of orbital contributors. For the main band in the visible region, besides the recently reported thiolate-to-superoxide charge transfer, a more salient, and less functional-dependent, feature is a thiolate-to-ferric iron charge transfer, consistent with a ferric-peroxo electromer. By contrast, the computed UV-vis spectra of a ferric-hydroperoxo SOR model match distinctly better (and with no qualitative dependence on the DFT methodology) the 600-nm band as due to a mainly thiolate-to-ferric character - supporting the assignment of the SOR "600-nm intermediate" as a S=5/2 ferric-hydroperoxo species.
Collapse
Affiliation(s)
- Amr A A Attia
- Department of Chemistry, Faculty of Chemistry and Chemical Engineering, Babeş-Bolyai University, Cluj-Napoca, Romania
| | - Daniela Cioloboc
- Department of Chemistry, University of Texas at San Antonio, San Antonio, TX 78249, United States
| | - Alexandru Lupan
- Department of Chemistry, Faculty of Chemistry and Chemical Engineering, Babeş-Bolyai University, Cluj-Napoca, Romania
| | - Radu Silaghi-Dumitrescu
- Department of Chemistry, Faculty of Chemistry and Chemical Engineering, Babeş-Bolyai University, Cluj-Napoca, Romania.
| |
Collapse
|
22
|
Nastri F, Chino M, Maglio O, Bhagi-Damodaran A, Lu Y, Lombardi A. Design and engineering of artificial oxygen-activating metalloenzymes. Chem Soc Rev 2016; 45:5020-54. [PMID: 27341693 PMCID: PMC5021598 DOI: 10.1039/c5cs00923e] [Citation(s) in RCA: 133] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Many efforts are being made in the design and engineering of metalloenzymes with catalytic properties fulfilling the needs of practical applications. Progress in this field has recently been accelerated by advances in computational, molecular and structural biology. This review article focuses on the recent examples of oxygen-activating metalloenzymes, developed through the strategies of de novo design, miniaturization processes and protein redesign. Considerable progress in these diverse design approaches has produced many metal-containing biocatalysts able to adopt the functions of native enzymes or even novel functions beyond those found in Nature.
Collapse
Affiliation(s)
- Flavia Nastri
- Department of Chemical Sciences, University of Naples “Federico II”, Via Cintia, 80126 Naples, Italy
| | - Marco Chino
- Department of Chemical Sciences, University of Naples “Federico II”, Via Cintia, 80126 Naples, Italy
| | - Ornella Maglio
- Department of Chemical Sciences, University of Naples “Federico II”, Via Cintia, 80126 Naples, Italy
- IBB, CNR, Via Mezzocannone 16, 80134 Naples, Italy
| | - Ambika Bhagi-Damodaran
- Department of Chemistry, University of Illinois at Urbana-Champaign, A322 CLSL, 600 South Mathews Avenue, Urbana, IL 61801
| | - Yi Lu
- Department of Chemistry, University of Illinois at Urbana-Champaign, A322 CLSL, 600 South Mathews Avenue, Urbana, IL 61801
| | - Angela Lombardi
- Department of Chemical Sciences, University of Naples “Federico II”, Via Cintia, 80126 Naples, Italy
| |
Collapse
|
23
|
Davydov R, Im S, Shanmugam M, Gunderson WA, Pearl NM, Hoffman BM, Waskell L. Role of the Proximal Cysteine Hydrogen Bonding Interaction in Cytochrome P450 2B4 Studied by Cryoreduction, Electron Paramagnetic Resonance, and Electron-Nuclear Double Resonance Spectroscopy. Biochemistry 2016; 55:869-83. [PMID: 26750753 DOI: 10.1021/acs.biochem.5b00744] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Crystallographic studies have shown that the F429H mutation of cytochrome P450 2B4 introduces an H-bond between His429 and the proximal thiolate ligand, Cys436, without altering the protein fold but sharply decreases the enzymatic activity and stabilizes the oxyferrous P450 2B4 complex. To characterize the influence of this hydrogen bond on the states of the catalytic cycle, we have used radiolytic cryoreduction combined with electron paramagnetic resonance (EPR) and (electron-nuclear double resonance (ENDOR) spectroscopy to study and compare their characteristics for wild-type (WT) P450 2B4 and the F429H mutant. (i) The addition of an H-bond to the axial Cys436 thiolate significantly changes the EPR signals of both low-spin and high-spin heme-iron(III) and the hyperfine couplings of the heme-pyrrole (14)N but has relatively little effect on the (1)H ENDOR spectra of the water ligand in the six-coordinate low-spin ferriheme state. These changes indicate that the H-bond introduced between His and the proximal cysteine decreases the extent of S → Fe electron donation and weakens the Fe(III)-S bond. (ii) The added H-bond changes the primary product of cryoreduction of the Fe(II) enzyme, which is trapped in the conformation of the parent Fe(II) state. In the wild-type enzyme, the added electron localizes on the porphyrin, generating an S = (3)/2 state with the anion radical exchange-coupled to the Fe(II). In the mutant, it localizes on the iron, generating an S = (1)/2 Fe(I) state. (iii) The additional H-bond has little effect on g values and (1)H-(14)N hyperfine couplings of the cryogenerated, ferric hydroperoxo intermediate but noticeably slows its decay during cryoannealing. (iv) In both the WT and the mutant enzyme, this decay shows a significant solvent kinetic isotope effect, indicating that the decay reflects a proton-assisted conversion to Compound I (Cpd I). (v) We confirm that Cpd I formed during the annealing of the cryogenerated hydroperoxy intermediate and that it is the active hydroxylating species in both WT P450 2B4 and the F429H mutant. (vi) Our data also indicate that the added H-bond of the mutation diminishes the reactivity of Cpd I.
Collapse
Affiliation(s)
- Roman Davydov
- Department of Chemistry, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Sangchoul Im
- Department of Anesthesiology, University of Michigan, and VA Medical Center , 2215 Fuller Road, Ann Arbor, Michigan 48105, United States
| | - Muralidharan Shanmugam
- Department of Chemistry, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - William A Gunderson
- Department of Chemistry, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Naw May Pearl
- Department of Anesthesiology, University of Michigan, and VA Medical Center , 2215 Fuller Road, Ann Arbor, Michigan 48105, United States
| | - Brian M Hoffman
- Department of Chemistry, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Lucy Waskell
- Department of Anesthesiology, University of Michigan, and VA Medical Center , 2215 Fuller Road, Ann Arbor, Michigan 48105, United States
| |
Collapse
|
24
|
Gennari M, Brazzolotto D, Pécaut J, Cherrier MV, Pollock CJ, DeBeer S, Retegan M, Pantazis DA, Neese F, Rouzières M, Clérac R, Duboc C. Dioxygen Activation and Catalytic Reduction to Hydrogen Peroxide by a Thiolate-Bridged Dimanganese(II) Complex with a Pendant Thiol. J Am Chem Soc 2015; 137:8644-53. [DOI: 10.1021/jacs.5b04917] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Affiliation(s)
- Marcello Gennari
- CNRS
UMR 5250, DCM, Université Grenoble Alpes, F-38000 Grenoble, France
| | | | - Jacques Pécaut
- INAC-SCIB, Université Grenoble Alpes, F-38000 Grenoble, France
- Reconnaissance Ionique et Chimie de Coordination, CEA, INAC-SCIB, F-38000 Grenoble, France
| | - Mickael V. Cherrier
- Metalloproteins
Unit, Institut de Biologie Structurale Jean-Pierre Ebel, CEA, CNRS
UMR 5075, Université Grenoble Alpes, 41 rue Horowitz, 38027 Grenoble Cedex 1, France
- Université de Lyon, F-69622 Lyon, France
- Université Claude Bernard Lyon 1, F-69622 Villeurbanne, France
- CNRS,
UMR 5086 Bases Moléculaires et Structurales de Systèmes
Infectieux, Institut de Biologie et Chimie des Protéines, 7 Passage du Vercors, F-69367 Lyon, France
| | - Christopher J. Pollock
- Max-Planck-Institut für Chemische Energie Konversion, Stiftstrasse 34-36, D-45470 Mülheim an der Ruhr, Germany
| | - Serena DeBeer
- Max-Planck-Institut für Chemische Energie Konversion, Stiftstrasse 34-36, D-45470 Mülheim an der Ruhr, Germany
- Department
of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States
| | - Marius Retegan
- Max-Planck-Institut für Chemische Energie Konversion, Stiftstrasse 34-36, D-45470 Mülheim an der Ruhr, Germany
| | - Dimitrios A. Pantazis
- Max-Planck-Institut für Chemische Energie Konversion, Stiftstrasse 34-36, D-45470 Mülheim an der Ruhr, Germany
| | - Frank Neese
- Max-Planck-Institut für Chemische Energie Konversion, Stiftstrasse 34-36, D-45470 Mülheim an der Ruhr, Germany
| | - Mathieu Rouzières
- CNRS, CRPP, UPR 8641, F-33600 Pessac, France
- CRPP,
UPR 8641, Université Bordeaux, F-33600 Pessac, France
| | - Rodolphe Clérac
- CNRS, CRPP, UPR 8641, F-33600 Pessac, France
- CRPP,
UPR 8641, Université Bordeaux, F-33600 Pessac, France
| | - Carole Duboc
- CNRS
UMR 5250, DCM, Université Grenoble Alpes, F-38000 Grenoble, France
| |
Collapse
|
25
|
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.
Collapse
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:
| |
Collapse
|
26
|
Liu J, Meier KK, Tian S, Zhang JL, Guo H, Schulz CE, Robinson H, Nilges MJ, Münck E, Lu Y. Redesigning the blue copper azurin into a redox-active mononuclear nonheme iron protein: preparation and study of Fe(II)-M121E azurin. J Am Chem Soc 2014; 136:12337-44. [PMID: 25082811 DOI: 10.1021/ja505410u] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Much progress has been made in designing heme and dinuclear nonheme iron enzymes. In contrast, engineering mononuclear nonheme iron enzymes is lagging, even though these enzymes belong to a large class that catalyzes quite diverse reactions. Herein we report spectroscopic and X-ray crystallographic studies of Fe(II)-M121E azurin (Az), by replacing the axial Met121 and Cu(II) in wild-type azurin (wtAz) with Glu and Fe(II), respectively. In contrast to the redox inactive Fe(II)-wtAz, the Fe(II)-M121EAz mutant can be readily oxidized by Na2IrCl6, and interestingly, the protein exhibits superoxide scavenging activity. Mössbauer and EPR spectroscopies, along with X-ray structural comparisons, revealed similarities and differences between Fe(II)-M121EAz, Fe(II)-wtAz, and superoxide reductase (SOR) and allowed design of the second generation mutant, Fe(II)-M121EM44KAz, that exhibits increased superoxide scavenging activity by 2 orders of magnitude. This finding demonstrates the importance of noncovalent secondary coordination sphere interactions in fine-tuning enzymatic activity.
Collapse
Affiliation(s)
- Jing Liu
- Department of Chemistry, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
| | | | | | | | | | | | | | | | | | | |
Collapse
|
27
|
Widger LR, Jiang Y, McQuilken AC, Yang T, Siegler MA, Matsumura H, Moënne-Loccoz P, Kumar D, de Visser SP, Goldberg DP. Thioether-ligated iron(II) and iron(III)-hydroperoxo/alkylperoxo complexes with an H-bond donor in the second coordination sphere. Dalton Trans 2014; 43:7522-32. [PMID: 24705907 PMCID: PMC4319814 DOI: 10.1039/c4dt00281d] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The non-heme iron complexes, [Fe(II)(N3PySR)(CH3CN)](BF4)2 () and [Fe(II)(N3Py(amide)SR)](BF4)2 (), afford rare examples of metastable Fe(iii)-OOH and Fe(iii)-OOtBu complexes containing equatorial thioether ligands and a single H-bond donor in the second coordination sphere. These peroxo complexes were characterized by a range of spectroscopic methods and density functional theory studies. The influence of a thioether ligand and of one H-bond donor on the stability and spectroscopic properties of these complexes was investigated.
Collapse
Affiliation(s)
- Leland R Widger
- Department of Chemistry, The Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, USA.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
28
|
Kimura M, Umemoto Y, Kawano T. Hydrogen peroxide-independent generation of superoxide by plant peroxidase: hypotheses and supportive data employing ferrous ion as a model stimulus. FRONTIERS IN PLANT SCIENCE 2014; 5:285. [PMID: 25071789 PMCID: PMC4077124 DOI: 10.3389/fpls.2014.00285] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2014] [Accepted: 06/02/2014] [Indexed: 05/05/2023]
Abstract
When plants are threaten by microbial attacks or treated with elicitors, alkalization of extracellular space is often induced and thus pH-dependent extracellular peroxidase-mediated oxidative burst reportedly takes place, especially at the site of microbial challenge. However, direct stimulus involved in activation of peroxidase-catalyzed oxidative burst has not been identified to date. Here, we would like to propose a likely role for free ferrous ion in reduction of ferric native peroxidase into ferrous enzyme intermediate which readily produces superoxide anion via mechanism involving Compound III, especially under alkaline condition, thus, possibly contributing to the plant defense mechanism. Through spectroscopic and chemiluminescence (CL) analyses of reactions catalyzed by horseradish peroxidase (HRP), the present study proposed that plant peroxidase-catalyzed production of superoxide anion can be stimulated in the absence of conventional peroxidase substrates but in the presence of free ferrous ion.
Collapse
Affiliation(s)
| | | | - Tomonori Kawano
- *Correspondence: Tomonori Kawano, University of Kitakyushu, 1-1 Hibikino, Wakamatsu-ku, Fukuoka, Kitakyushu 808-0135, Japan e-mail:
| |
Collapse
|
29
|
Hong S, Lee YM, Cho KB, Seo MS, Song D, Yoon J, Garcia-Serres R, Clémancey M, Ogura T, Shin W, Latour JM, Nam W. Conversion of high-spin iron(iii)–alkylperoxo to iron(iv)–oxo species via O–O bond homolysis in nonheme iron models. Chem Sci 2014. [DOI: 10.1039/c3sc52236a] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
|
30
|
Horch M, Pinto AF, Utesch T, Mroginski MA, Romão CV, Teixeira M, Hildebrandt P, Zebger I. Reductive activation and structural rearrangement in superoxide reductase: a combined infrared spectroscopic and computational study. Phys Chem Chem Phys 2014; 16:14220-30. [DOI: 10.1039/c4cp00884g] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Local and global structural changes that enable reductive activation of superoxide reductase are revealed by a combined approach of infrared difference spectroscopy and computational methods.
Collapse
Affiliation(s)
- M. Horch
- Technische Universität Berlin
- Institut für Chemie
- 10623 Berlin, Germany
| | - A. F. Pinto
- Instituto de Tecnologia Química e Biológica António Xavier
- Universidade Nova de Lisboa
- Av. da República (EAN)
- P-2780-157 Oeiras, Portugal
| | - T. Utesch
- Technische Universität Berlin
- Institut für Chemie
- 10623 Berlin, Germany
| | - M. A. Mroginski
- Technische Universität Berlin
- Institut für Chemie
- 10623 Berlin, Germany
| | - C. V. Romão
- Instituto de Tecnologia Química e Biológica António Xavier
- Universidade Nova de Lisboa
- Av. da República (EAN)
- P-2780-157 Oeiras, Portugal
| | - M. Teixeira
- Instituto de Tecnologia Química e Biológica António Xavier
- Universidade Nova de Lisboa
- Av. da República (EAN)
- P-2780-157 Oeiras, Portugal
| | - P. Hildebrandt
- Technische Universität Berlin
- Institut für Chemie
- 10623 Berlin, Germany
| | - I. Zebger
- Technische Universität Berlin
- Institut für Chemie
- 10623 Berlin, Germany
| |
Collapse
|
31
|
SEE RONALDF, KOZINA DANIEL. Quantification of the trans influence in d8 square planar and d6 octahedral complexes: a database study. J COORD CHEM 2013. [DOI: 10.1080/00958972.2012.758842] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Affiliation(s)
- RONALD F. SEE
- a Department of Chemistry , Indiana University of Pennsylvania , Indiana , PA , USA
| | | |
Collapse
|
32
|
Iron(II) α-Aminopyridine Complexes and Their Catalytic Activity in Oxidation Reactions: A Comparative Study of Activity and Ligand Decomposition. Chempluschem 2012. [DOI: 10.1002/cplu.201200244] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
|
33
|
McDonald AR, Van Heuvelen KM, Guo Y, Li F, Bominaar EL, Münck E, Que L. Characterization of a thiolato iron(III) Peroxy dianion complex. Angew Chem Int Ed Engl 2012; 51:9132-6. [PMID: 22888066 PMCID: PMC3448492 DOI: 10.1002/anie.201203602] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2012] [Revised: 06/19/2012] [Indexed: 11/09/2022]
Abstract
Nucleophilic oxidant: The reaction between a thiolato iron(II) complex 1 and superoxide in aprotic solvent at -90 °C yields a novel thiolato iron(III) peroxide intermediate 2, which exhibits unusually high nucleophilic reactivity. Compound 2 is an isomer of the thiolato iron(II) superoxide intermediate that is invoked in the reaction between superoxide reductase and superoxide.
Collapse
Affiliation(s)
- Aidan R. McDonald
- Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, MN 55455, USA
| | - Katherine M. Van Heuvelen
- Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, MN 55455, USA
| | - Yisong Guo
- Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, PA 15213, USA
| | - Feifei Li
- Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, MN 55455, USA
| | - Emile L. Bominaar
- Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, PA 15213, USA
| | - Eckard Münck
- Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, PA 15213, USA
| | - Lawrence Que
- Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, MN 55455, USA
| |
Collapse
|
34
|
Tano T, Sugimoto H, Fujieda N, Itoh S. Heterolytic Alkyl Hydroperoxide O-O Bond Cleavage by Copper(I) Complexes. Eur J Inorg Chem 2012. [DOI: 10.1002/ejic.201200555] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
35
|
McDonald AR, Van Heuvelen KM, Guo Y, Li F, Bominaar EL, Münck E, Que L. Characterization of a Thiolato Iron(III) Peroxy Dianion Complex. Angew Chem Int Ed Engl 2012. [DOI: 10.1002/ange.201203602] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|
36
|
Wächtler M, Guthmuller J, González L, Dietzek B. Analysis and characterization of coordination compounds by resonance Raman spectroscopy. Coord Chem Rev 2012. [DOI: 10.1016/j.ccr.2012.02.004] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
|
37
|
Gonzalez-Ovalle LE, Quesne MG, Kumar D, Goldberg DP, de Visser SP. Axial and equatorial ligand effects on biomimetic cysteine dioxygenase model complexes. Org Biomol Chem 2012; 10:5401-9. [PMID: 22714822 PMCID: PMC3454459 DOI: 10.1039/c2ob25406a] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Density functional theory (DFT) calculations are presented on biomimetic model complexes of cysteine dioxygenase and focus on the effect of axial and equatorial ligand placement. Recent studies by one of us [Y. M. Badiei, M. A. Siegler and D. P. Goldberg, J. Am. Chem. Soc. 2011, 133, 1274] gave evidence of a nonheme iron biomimetic model of cysteine dioxygenase using an i-propyl-bis(imino)pyridine, equatorial tridentate ligand. Addition of thiophenol, an anion - either chloride or triflate - and molecular oxygen, led to several possible stereoisomers of this cysteine dioxygenase biomimetic complex. Moreover, large differences in reactivity using chloride as compared to triflate as the binding anion were observed. Here we present a series of DFT calculations on the origin of these reactivity differences and show that it is caused by the preference of coordination site of anion versus thiophenol binding to the chemical system. Thus, stereochemical interactions of triflate and the bulky iso-propyl substituents of the ligand prevent binding of thiophenol in the trans position using triflate. By contrast, smaller anions, such as chloride, can bind in either cis or trans ligand positions and give isomers with similar stability. Our calculations help to explain the observance of thiophenol dioxygenation by this biomimetic system and gives details of the reactivity differences of ligated chloride versus triflate.
Collapse
Affiliation(s)
- Luis E. Gonzalez-Ovalle
- Manchester Interdisciplinary Biocenter and School of Chemical Engineering and Analytical Science, University of Manchester, 131 Princess Street, Manchester M1 7DN, UK. Fax: +44 161306 5201
| | - Matthew G. Quesne
- Manchester Interdisciplinary Biocenter and School of Chemical Engineering and Analytical Science, University of Manchester, 131 Princess Street, Manchester M1 7DN, UK. Fax: +44 161306 5201
| | - Devesh Kumar
- Department of Applied Physics, School of Physical Sciences, Babasaheb, Bhimrao Ambedkar University, Vidya Vihar, Rae Bareilly Road, Lucknow 226-025, India
| | - David P. Goldberg
- Department of Chemistry, Johns Hopkins University, 3400 N. Charles Street, Baltimore, Maryland 21218, USA
| | - Sam P. de Visser
- Manchester Interdisciplinary Biocenter and School of Chemical Engineering and Analytical Science, University of Manchester, 131 Princess Street, Manchester M1 7DN, UK. Fax: +44 161306 5201
| |
Collapse
|
38
|
McQuilken AC, Jiang Y, Siegler MA, Goldberg DP. Addition of dioxygen to an N4S(thiolate) iron(II) cysteine dioxygenase model gives a structurally characterized sulfinato-iron(II) complex. J Am Chem Soc 2012; 134:8758-61. [PMID: 22578255 PMCID: PMC3403739 DOI: 10.1021/ja302112y] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The non-heme iron enzyme cysteine dioxygenase (CDO) catalyzes the S-oxygenation of cysteine by O(2) to give cysteine sulfinic acid. The synthesis of a new structural and functional model of the cysteine-bound CDO active site, [Fe(II)(N3PyS)(CH(3)CN)]BF(4) (1) is reported. This complex was prepared with a new facially chelating 4N/1S(thiolate) pentadentate ligand. The reaction of 1 with O(2) resulted in oxygenation of the thiolate donor to afford the doubly oxygenated sulfinate product [Fe(II)(N3PySO(2))(NCS)] (2), which was crystallographically characterized. The thiolate donor provided by the new N3PyS ligand has a dramatic influence on the redox potential and O(2) reactivity of this Fe(II) model complex.
Collapse
Affiliation(s)
- Alison C. McQuilken
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland, 21218, United States
| | - Yunbo Jiang
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland, 21218, United States
| | - Maxime A. Siegler
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland, 21218, United States
| | - David P. Goldberg
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland, 21218, United States
| |
Collapse
|
39
|
Ye W, Staples RJ, Rybak-Akimova EV. Oxygen atom transfer mediated by an iron(IV)/iron(II) macrocyclic complex containing pyridine and tertiary amine donors. J Inorg Biochem 2012; 115:1-12. [PMID: 22922287 DOI: 10.1016/j.jinorgbio.2012.05.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2011] [Revised: 05/08/2012] [Accepted: 05/10/2012] [Indexed: 11/19/2022]
Abstract
A new non-heme iron model complex containing a high-spin iron(II) complexed with N-methylated pyridine-containing macrocycle was synthesized and crystallographically characterized. The complex generates peroxo- and high-valent iron-oxo intermediates in reactions with tert-butylhydroperoxide and isopropyl 2-iodoxybenzoate, respectively, allowing to gain insight into the formation and reactivity of enzyme-like intermediates related to biological oxygen activation. The formation and reactivity of these intermediate species were investigated by the stopped-flow methodology. The mechanism of oxygen transfer to organic substrates involving reaction of oxoiron(IV) intermediate was elucidated on the basis of spectroscopic and kinetic data. Incorporation of a pyridine ring into the macrocycle increased the reactivity of the Fe(IV)=O intermediates in comparison with polyamine tetraaza macrocyclic complexes: ferryl (Fe(IV)=O) species derived from 3 demonstrated electrophilic reactivity in transferring an oxygen atom to substituted triarylphosphines and to olefins (such as cyclooctene). However, iron(III) alkylperoxo intermediate was unreactive with cyclooctene.
Collapse
Affiliation(s)
- Wanhua Ye
- Department of Chemistry, Tufts University, Medford, MA 02155, USA
| | | | | |
Collapse
|
40
|
Preparation of aluminum(III) (bis(amido)pyridine)(thiolate) complexes: unexpected transmetalation mediated by LiAlH(4). Inorganica Chim Acta 2012; 382:19-26. [PMID: 22345823 DOI: 10.1016/j.ica.2011.09.056] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Treatment of an unsymmetrical bis(imino)pyridyl-thiolate zinc(II) complex [Zn(II)(LN(3)S)(OTf)] (1) with LiAlH(4) results in the double reduction of the two imino groups in the ligand backbone, and at the same time causes a rare transmetalation reaction to occur. The products formed in this reaction are two novel aluminium(III) bis(amido)pyridyl-thiolate complexes [(R,S/S,R-[Al(III)(LH(2)N(3)S)(THF)] (2a) and [(R,R/S,S-[Al(III)(LH(2)N(3)S)(THF)] (2b), which are diastereomers of each other. These complexes have been characterized by single-crystal X-ray diffraction and (1)H NMR spectroscopy. Single crystal X-ray structure analysis shows that the Al(III) ion is bound in an almost idealized square pyramidal geometry in 2a, while being held in a more distorted square pyramidal geometry in 2b. The major difference between 2a and 2b arises in the orientation of the terminal methyl groups of the ligand backbone in relation to the Al(III)N(3)S plane. These two complexes are crystallized at different temperatures (room temperature vs -35 °C), allowing for their separate isolation. Structural analysis shows that these complexes are reduced by the formal addition of one hydride ion to each imino group, resulting in a deprotonated bis(amido)pyridyl-thiolate ligand. A detailed analysis of metrical parameters rules out the possibility of pure one- or two-electron reduction of the π-conjugated bis(imino)pyridine framework. (1)H NMR spectra reveal a rich pattern in solution indicating that the solution state structures for 2a and 2b match those observed in the solid-state crystal structures, and reveal that both complexes are severely conformationally restricted. Direct organic synthetic methods failed to produce the reduced bis(amino)pyridyl-thiol ligand in pure form, but during the course of these efforts an unusual unsymmetrical aminopyridyl ketone, 1-(6-(1-(2,6-diisopropylphenylamino)ethyl)pyridin-2-yl)ethanone was synthesized in good yield and can be used as a possible precursor for further ligand development.
Collapse
|
41
|
Kumar D, Sastry GN, Goldberg DP, de Visser SP. Mechanism of S-oxygenation by a cysteine dioxygenase model complex. J Phys Chem A 2011; 116:582-91. [PMID: 22091701 DOI: 10.1021/jp208230g] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
In this work, we present the first computational study on a biomimetic cysteine dioxygenase model complex, [Fe(II)(LN(3)S)](+), in which LN(3)S is a tetradentate ligand with a bis(imino)pyridyl scaffold and a pendant arylthiolate group. The reaction mechanism of sulfur dioxygenation with O(2) was examined by density functional theory (DFT) methods and compared with results obtained for cysteine dioxygenase. The reaction proceeds via multistate reactivity patterns on competing singlet, triplet, and quintet spin state surfaces. The reaction mechanism is analogous to that found for cysteine dioxygenase enzymes (Kumar, D.; Thiel, W.; de Visser, S. P. J. Am. Chem. Soc. 2011, 133, 3869-3882); hence, the computations indicate that this complex can closely mimic the enzymatic process. The catalytic mechanism starts from an iron(III)-superoxo complex and the attack of the terminal oxygen atom of the superoxo group on the sulfur atom of the ligand. Subsequently, the dioxygen bond breaks to form an iron(IV)-oxo complex with a bound sulfenato group. After reorganization, the second oxygen atom is transferred to the substrate to give a sulfinic acid product. An alternative mechanism involving the direct attack of dioxygen on the sulfur, without involving any iron-oxygen intermediates, was also examined. Importantly, a significant energetic preference for dioxygen coordinating to the iron center prior to attack at sulfur was discovered and serves to elucidate the function of the metal ion in the reaction process. The computational results are in good agreement with experimental observations, and the differences and similarities of the biomimetic complex and the enzymatic cysteine dioxygenase center are highlighted.
Collapse
Affiliation(s)
- Devesh Kumar
- Molecular Modelling Group, Indian Institute of Chemical Technology, Hyderabad 500-607, India.
| | | | | | | |
Collapse
|
42
|
Tano T, Ertem MZ, Yamaguchi S, Kunishita A, Sugimoto H, Fujieda N, Ogura T, Cramer CJ, Itoh S. Reactivity of copper(II)-alkylperoxo complexes. Dalton Trans 2011; 40:10326-36. [PMID: 21808769 DOI: 10.1039/c1dt10656b] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Copper(II) complexes 1a and 1b, supported by tridentate ligand bpa [bis(2-pyridylmethyl)amine] and tetradentate ligand tpa [tris(2-pyridylmethyl)amine], respectively, react with cumene hydroperoxide (CmOOH) in the presence of triethylamine in CH(3)CN to provide the corresponding copper(II) cumylperoxo complexes 2a and 2b, the formation of which has been confirmed by resonance Raman and ESI-MS analyses using (18)O-labeled CmOOH. UV-vis and ESR spectra as well as DFT calculations indicate that 2a has a 5-coordinate square-pyramidal structure involving CmOO(-) at an equatorial position and one solvent molecule at an axial position at low temperature (-90 °C), whereas a 4-coordinate square-planar structure that has lost the axial solvent ligand is predominant at higher temperatures (above 0 °C). Complex 2b, on the other hand, has a typical trigonal bipyramidal structure with the tripodal tetradentate tpa ligand, where the cumylperoxo ligand occupies an axial position. Both cumylperoxo copper(II) complexes 2a and 2b are fairly stable at ambient temperature, but decompose at a higher temperature (60 °C) in CH(3)CN. Detailed product analyses and DFT studies indicate that the self-decomposition involves O-O bond homolytic cleavage of the peroxo moiety; concomitant hydrogen-atom abstraction from the solvent is partially involved. In the presence of 1,4-cyclohexadiene (CHD), the cumylperoxo complexes react smoothly at 30 °C to give benzene as one product. Detailed product analyses and DFT studies indicate that reaction with CHD involves concerted O-O bond homolytic cleavage and hydrogen-atom abstraction from the substrate, with the oxygen atom directly bonded to the copper(II) ion (proximal oxygen) involved in the C-H bond activation step.
Collapse
Affiliation(s)
- Tetsuro Tano
- Department of Material and Life Science, Division of Advanced Science and Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871, Japan
| | | | | | | | | | | | | | | | | |
Collapse
|
43
|
Coggins MK, Kovacs JA. Structural and spectroscopic characterization of metastable thiolate-ligated manganese(III)-alkylperoxo species. J Am Chem Soc 2011; 133:12470-3. [PMID: 21776951 DOI: 10.1021/ja205520u] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Metastable Mn-peroxo species are proposed to form as key intermediates in biological oxidation reactions involving O(2) and C-H bond activation. The majority of these have yet to be spectroscopically characterized, and their inherent instability, in most cases, precludes structural characterization. Cysteinate-ligated metal-peroxos have been shown to form as reactive intermediates in both heme and nonheme iron enzymes. Herein we report the only examples of isolable Mn(III)-alkylperoxo species, and the first two examples of structurally characterized synthetic thiolate-ligated metal-peroxos. Spectroscopic data, including electronic absorption and IR spectra, and ESI mass spectra for (16)O vs (18)O-labeled metastable Mn(III)-OOR (R = (t)Bu, Cm) are discussed, as well as preliminary reactivity.
Collapse
Affiliation(s)
- Michael K Coggins
- Department of Chemistry, University of Washington, Seattle, Washington 98195, United States
| | | |
Collapse
|
44
|
Villar-Acevedo G, Nam E, Fitch S, Benedict J, Freudenthal J, Kaminsky W, Kovacs JA. Influence of thiolate ligands on reductive N-O bond activation. Probing the O2(-) binding site of a biomimetic superoxide reductase analogue and examining the proton-dependent reduction of nitrite. J Am Chem Soc 2011; 133:1419-27. [PMID: 21207999 PMCID: PMC3178331 DOI: 10.1021/ja107551u] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Nitric oxide (NO) is frequently used to probe the substrate-binding site of "spectroscopically silent" non-heme Fe(2+) sites of metalloenzymes, such as superoxide reductase (SOR). Herein we use NO to probe the superoxide binding site of our thiolate-ligated biomimetic SOR model [Fe(II)(S(Me(2))N(4)(tren))](+) (1). Like NO-bound trans-cysteinate-ligated SOR (SOR-NO), the rhombic S = 3/2 EPR signal of NO-bound cis-thiolate-ligated [Fe(S(Me(2))N(4)(tren)(NO)](+) (2; g = 4.44, 3.54, 1.97), the isotopically sensitive ν(NO)(ν((15)NO)) stretching frequency (1685(1640) cm(-1)), and the 0.05 Å decrease in Fe-S bond length are shown to be consistent with the oxidative addition of NO to Fe(II) to afford an Fe(III)-NO(-) {FeNO}(7) species containing high-spin (S = 5/2) Fe(III) antiferromagnetically coupled to NO(-) (S = 1). The cis versus trans positioning of the thiolate does not appear to influence these properties. Although it has yet to be crystallographically characterized, SOR-NO is presumed to possess a bent Fe-NO similar to that of 2 (Fe-N-O = 151.7(4)°). The N-O bond is shown to be more activated in 2 relative to N- and O-ligated {FeNO}(7) complexes, and this is attributed to the electron-donating properties of the thiolate ligand. Hydrogen-bonding to the cysteinate sulfur attenuates N-O bond activation in SOR, as shown by its higher ν(NO) frequency (1721 cm(-1)). In contrast, the ν(O-O) frequency of the SOR peroxo intermediate and its analogues is not affected by H-bonds to the cysteinate sulfur or other factors influencing the Fe-SR bond strength; these only influence the ν(Fe-O) frequency. Reactions between 1 and NO(2)(-) are shown to result in the proton-dependent heterolytic cleavage of an N-O bond. The mechanism of this reaction is proposed to involve both Fe(II)-NO(2)(-) and {FeNO}(6) intermediates similar to those implicated in the mechanism of NiR-promoted NO(2)(-) reduction.
Collapse
Affiliation(s)
| | - Elaine Nam
- Department of Chemistry, University of Washington, Seattle, WA 98195
| | - Sarah Fitch
- Department of Chemistry, University of Washington, Seattle, WA 98195
| | | | | | | | - Julie A. Kovacs
- Department of Chemistry, University of Washington, Seattle, WA 98195
| |
Collapse
|
45
|
Stasser J, Namuswe F, Kasper GD, Jiang Y, Krest CM, Green MT, Penner-Hahn J, Goldberg DP. X-ray absorption spectroscopy and reactivity of thiolate-ligated Fe(III)-OOR complexes. Inorg Chem 2011; 49:9178-90. [PMID: 20839847 DOI: 10.1021/ic100670k] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The reaction of a series of thiolate-ligated iron(II) complexes [Fe(II)([15]aneN(4))(SC(6)H(5))]BF(4) (1), [Fe(II)([15]aneN(4))(SC(6)H(4)-p-Cl)]BF(4) (2), and [Fe(II)([15]aneN(4))(SC(6)H(4)-p-NO(2))]BF(4) (3) with alkylhydroperoxides at low temperature (-78 °C or -40 °C) leads to the metastable alkylperoxo-iron(III) species [Fe(III)([15]aneN(4))(SC(6)H(5))(OOtBu)]BF(4) (1a), [Fe(III)([15]aneN(4))(SC(6)H(4)-p-Cl)(OOtBu)]BF(4) (2a), and [Fe(III)([15]aneN(4))(SC(6)H(4)-p-NO(2))(OOtBu)]BF(4) (3a), respectively. X-ray absorption spectroscopy (XAS) studies were conducted on the Fe(III)-OOR complexes and their iron(II) precursors. The edge energy for the iron(II) complexes (∼7118 eV) shifts to higher energy upon oxidation by ROOH, and the resulting edge energies for the Fe(III)-OOR species range from 7121-7125 eV and correlate with the nature of the thiolate donor. Extended X-ray absorption fine structure (EXAFS) analysis of the iron(II) complexes 1-3 in CH(2)Cl(2) show that their solid state structures remain intact in solution. The EXAFS data on 1a-3a confirm their proposed structures as mononuclear, 6-coordinate Fe(III)-OOR complexes with 4N and 1S donors completing the coordination sphere. The Fe-O bond distances obtained from EXAFS for 1a-3a are 1.82-1.85 Å, significantly longer than other low-spin Fe(III)-OOR complexes. The Fe-O distances correlate with the nature of the thiolate donor, in agreement with the previous trends observed for ν(Fe-O) from resonance Raman (RR) spectroscopy, and supported by optimized geometries obtained from density functional theory (DFT) calculations. Reactivity and kinetic studies on 1a- 3a show an important influence of the thiolate donor.
Collapse
Affiliation(s)
- Jay Stasser
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, USA
| | | | | | | | | | | | | | | |
Collapse
|
46
|
Loas A, Gerdes R, Zhang Y, Gorun SM. Broadening the reactivity spectrum of a phthalocyanine catalyst while suppressing its nucleophilic, electrophilic and radical degradation pathways. Dalton Trans 2011; 40:5162-5. [DOI: 10.1039/c1dt10458f] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
47
|
Shejwalkar P, Rath NP, Bauer EB. New iron(ii) α-iminopyridine complexes and their catalytic activity in the oxidation of activated methylene groups and secondary alcohols to ketones. Dalton Trans 2011; 40:7617-31. [DOI: 10.1039/c1dt10387c] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
48
|
McDonald AR, Bukowski MR, Farquhar ER, Jackson TA, Koehntop KD, Seo MS, De Hont RF, Stubna A, Halfen JA, Münck E, Nam W, Que L. Sulfur versus iron oxidation in an iron-thiolate model complex. J Am Chem Soc 2010; 132:17118-29. [PMID: 21070030 DOI: 10.1021/ja1045428] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In the absence of base, the reaction of [Fe(II)(TMCS)]PF6 (1, TMCS = 1-(2-mercaptoethyl)-4,8,11-trimethyl-1,4,8,11-tetraazacyclotetradecane) with peracid in methanol at -20 °C did not yield the oxoiron(IV) complex (2, [Fe(IV)(O)(TMCS)]PF6), as previously observed in the presence of strong base (KO(t)Bu). Instead, the addition of 1 equiv of peracid resulted in 50% consumption of 1. The addition of a second equivalent of peracid resulted in the complete consumption of 1 and the formation of a new species 3, as monitored by UV-vis, ESI-MS, and Mössbauer spectroscopies. ESI-MS showed 3 to be formulated as [Fe(II)(TMCS) + 2O](+), while EXAFS analysis suggested that 3 was an O-bound iron(II)-sulfinate complex (Fe-O = 1.95 Å, Fe-S = 3.26 Å). The addition of a third equivalent of peracid resulted in the formation of yet another compound, 4, which showed electronic absorption properties typical of an oxoiron(IV) species. Mössbauer spectroscopy confirmed 4 to be a novel iron(IV) compound, different from 2, and EXAFS (Fe═O = 1.64 Å) and resonance Raman (ν(Fe═O) = 831 cm(-1)) showed that indeed an oxoiron(IV) unit had been generated in 4. Furthermore, both infrared and Raman spectroscopy gave indications that 4 contains a metal-bound sulfinate moiety (ν(s)(SO2) ≈ 1000 cm (-1), ν(as)(SO2) ≈ 1150 cm (-1)). Investigations into the reactivity of 1 and 2 toward H(+) and oxygen atom transfer reagents have led to a mechanism for sulfur oxidation in which 2 could form even in the absence of base but is rapidly protonated to yield an oxoiron(IV) species with an uncoordinated thiol moiety that acts as both oxidant and substrate in the conversion of 2 to 3.
Collapse
Affiliation(s)
- Aidan R McDonald
- Department of Chemistry and Center for Metals in Biocatalysis, 207 Pleasant Street SE, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
49
|
Dey A, Solomon EI. Density Functional Theory Calculations on Fe-O and O-O Cleavage of Ferric Hydroperoxide Species: Role of axial ligand and spin state. Inorganica Chim Acta 2010; 363:2762-2767. [PMID: 21057606 DOI: 10.1016/j.ica.2010.03.059] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Density Functional Theory (DFT) calculations are performed on thiolate bound hydroperoxide complexes. O-O and Fe-O cleavage reaction coordinates, relevant to the active sites of Cytocrome P450 and Superoxide Reductase enzymes, were investigated for both high and low spin states and for cis and trans orientations of the thiolate ligand with respect to the hydroperoxide ligand. The results indicate that the presence of a thiolate ligand produces significant elongation of the Fe-O bond and reduction of Fe-O vibrational frequency. While the fate of the O-O cleavage reaction is not significantly altered, the presence of a thiolate induces a heterolytic Fe-O cleavage irrespective of the spin state and orientation which is very different from results obtained with a trans ammine ligand.
Collapse
Affiliation(s)
- Abhishek Dey
- Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, Kolkata, India, 700032
| | | |
Collapse
|
50
|
New chiral phosphoramidite complexes of iron as catalytic precursors in the oxidation of activated methylene groups. Molecules 2010; 15:2631-50. [PMID: 20428070 PMCID: PMC6257337 DOI: 10.3390/molecules15042631] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2010] [Revised: 03/31/2010] [Accepted: 04/06/2010] [Indexed: 11/17/2022] Open
Abstract
New phosphoramidite complexes of iron were synthesized and structurally characterized. Reaction of the known chiral phosphoramidites (RO)2PNR'2 (R = binaphthyl, R' = CH3, 1a; R = binaphthyl, R' = benzyl, 1b) with [FeBr(Cp)(CO)2] afforded the title compounds [FeBr(Cp)(CO)(1a,b)] (4a,b) in 34 and 65 % isolated yields as mixtures of diastereomers, since both the metal and the ligand are stereogenic. Similarly, reaction of 1b with [Fe(Cp)I(CO)2] in the presence of catalytic [Fe(Cp)(CO)2]2 afforded [Fe(Cp)I(CO)(1b)] (5b) in 81% yield as a mixture of diastereomers. The molecular structures of 4a, 4b and 5 were determined, revealing a pseudo octahedral coordination geometry about the iron center. The new metal complexes are catalytically active in the oxidation of benzylic methylene groups to the corresponding ketones, utilizing t-BuOOH as oxidant (2 mol% catalyst, 36 h, room temperature, 31-80% yield).
Collapse
|