1
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Marchi-Delapierre C, Cavazza C, Ménage S. EcNikA, a versatile tool in the field of artificial metalloenzymes. J Inorg Biochem 2025; 262:112740. [PMID: 39426332 DOI: 10.1016/j.jinorgbio.2024.112740] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2024] [Revised: 08/14/2024] [Accepted: 09/15/2024] [Indexed: 10/21/2024]
Abstract
This review describes the multiple advantages of using of EcNikA, a nickel transport protein, in the design of artificial metalloenzymes as alternative catalysts for synthetic biology. The rationale behind the strategy of artificial enzyme design is discussed, with particular emphasis on de novo active site reconstitution. The impact of the protein scaffold on the artificial active site and thus the final catalytic properties is detailed, highlighting the considerable aptitude of hybrid systems to catalyze selective reactions, from alkene to thioether transformations (epoxidation, hydroxychlorination, sulfoxidation). The different catalytic approaches - from in vitro to in cristallo - are compared, revealing the considerable advantages of protein crystals in terms of stabilization and acceleration of reaction kinetics. The versatility of proteins, based on metal and ligand diversity and medium/physical conditions, are thus illustrated for oxidation catalysis.
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Affiliation(s)
| | - Christine Cavazza
- Univ. Grenoble Alpes, CNRS, CEA, IRIG, CBM, F-38000 Grenoble, France
| | - Stéphane Ménage
- Univ. Grenoble Alpes, CNRS, CEA, IRIG, CBM, F-38000 Grenoble, France.
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2
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Das A, Pal N, Xiong J, Young VG, Guo Y, Swart M, Que L. 10-Fold Increase in Hydrogen Atom Transfer Reactivity for a Series of S = 1 Fe IV═O Complexes Over the S = 2 [(TQA)Fe IV═O] 2+ Complex via Entropic Lowering of Reaction Barriers by Secondary Sphere Cycloalkyl Substitution. J Am Chem Soc 2024. [PMID: 39699233 DOI: 10.1021/jacs.4c10120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2024]
Abstract
Nonheme iron enzymes utilize S = 2 iron(IV)-oxo intermediates as oxidants in biological oxygenations. In contrast, corresponding synthetic nonheme FeIV═O complexes characterized to date favor the S = 1 ground state that generally shows much poorer oxidative reactivity than their S = 2 counterparts. However, one intriguing exception found by Nam a decade ago is the S = 1 [FeIV(O)(Me3NTB)]2+ complex (Me3NTB = [tris((N-methyl-benzimidazol-2-yl)methyl)amine], 1O) with a hydrogen atom transfer (HAT) reactivity that is 70% that of the S = 2 [FeIV(O)(TQA)]2+ complex (TQA = tris(2-quinolylmethyl)amine, 3O). In our efforts to further explore this direction, we have unexpectedly uncovered a family of new S = 1 complexes with HAT reaction rates beyond the currently reported limits in the tripodal ligand family, surpassing oxidation rates found for the S = 2 [FeIV(O)(TQA)]2+ complex by as much as an order of magnitude. This is achieved simply by replacing the secondary sphere methyl groups of the Me3NTB ligand with larger cycloalkyl-CH2 (R groups in 2OR) moieties ranging from c-propylmethyl to c-hexylmethyl. These 2OR complexes show Mössbauer data at 4 K and 1H NMR spectra at 193 and 233 K that reveal S = 1 ground states, in line with DFT calculations. Nevertheless, they give rise to the most reactive synthetic nonheme oxoiron(IV) complexes found to date within the tripodal ligand family. Our DFT study indicates transition state stabilization through entropy effects, similar to enzymatic catalysis.
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Affiliation(s)
- Abhishek Das
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Nabhendu Pal
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Jin Xiong
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - Victor G Young
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Yisong Guo
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - Marcel Swart
- IQCC and Department of Chemistry, University of Girona, Girona 17003, Spain
- ICREA, Barcelona 08010, Spain
| | - Lawrence Que
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States
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3
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Sahoo L, Panwar P, Sastri CV, de Visser SP. Unraveling Chlorite Oxidation Pathways in Equatorially Heteroatom-Substituted Nonheme Iron Complexes. ACS ORGANIC & INORGANIC AU 2024; 4:673-680. [PMID: 39649995 PMCID: PMC11621950 DOI: 10.1021/acsorginorgau.4c00045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/18/2024] [Revised: 08/30/2024] [Accepted: 09/05/2024] [Indexed: 12/11/2024]
Abstract
The first-coordination sphere of catalysts is known to play a crucial role in reaction mechanisms, but details of how equatorial ligands influence the reactivity remain unknown. Heteroatom ligated to the equatorial position of iron centers in nonheme iron metalloenzymes modulates structure and reactivity. To investigate the impact of equatorial heteroatom substitution on chlorite oxidation, we synthesized and characterized three novel mononuclear nonheme iron(II) complexes with a pentadentate bispidine scaffold. These complexes feature systematic substitutions at the equatorial position in the bispidine ligand framework where the pyridine group is replaced with NMe2, SMe, and OMe groups. The three iron(II)-bispidine complexes were subjected to studies in chlorite oxidation reactions as a model pathway for oxygen atom transfer. Chlorine oxyanions, which have the halide in an oxidation state ranging from +1 to +7, have numerous applications but can contaminate water bodies, and this demands urgent environmental remediation. Chlorite, a common precursor to chlorine dioxide, is of particular interest due to the superior antimicrobial activity of chlorine dioxide. Moreover, its generation leads to fewer harmful byproducts in water treatment. Here, we demonstrate that these complexes can produce chlorine dioxide from chlorite in acetate buffer at room temperature and pH 5.0, oxidizing chlorite through the in situ formation of high-valent iron(IV)-oxo intermediates. This study establishes how subtle changes in the coordination sphere around iron can influence the reactivity.
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Affiliation(s)
- Limashree Sahoo
- Department
of Chemistry, Indian Institute of Technology
Guwahati, Assam 781039, India
| | - Payal Panwar
- Department
of Chemistry, Indian Institute of Technology
Guwahati, Assam 781039, India
| | - Chivukula V. Sastri
- Department
of Chemistry, Indian Institute of Technology
Guwahati, Assam 781039, India
| | - Sam P. de Visser
- Department
of Chemistry, Indian Institute of Technology
Guwahati, Assam 781039, India
- The
Manchester Institute of Biotechnology and Department of Chemical Engineering, The University of Manchester, 131 Princess Street, Manchester M1 7DN, U.K.
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4
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Mondal P, Udukalage D, Mohamed AA, Wong HPH, de Visser SP, Wijeratne GB. A Cytochrome P450 TxtE Model System with Mechanistic and Theoretical Evidence for a Heme Peroxynitrite Active Species. Angew Chem Int Ed Engl 2024; 63:e202409430. [PMID: 39088419 DOI: 10.1002/anie.202409430] [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: 05/18/2024] [Revised: 07/10/2024] [Accepted: 07/30/2024] [Indexed: 08/03/2024]
Abstract
The cytochrome P450 homolog, TxtE, efficiently catalyzes the direct and regioselective aromatic nitration of the indolyl moiety of L-tryptophan to 4-nitro-L-tryptophan, using nitric oxide (NO) and dioxygen (O2) as co-substrates. Pathways for such direct and selective nitration of heteroaromatic motifs present platforms for engineering new nitration biocatalysts for pharmacologically beneficial targets, among a medley of other pivotal industrial applications. Precise mechanistic details concerning this pathway are only weakly understood, albeit a heme iron(III)-peroxynitrite active species has been postulated. To shed light on this unique reaction landscape, we investigated the indole nitration pathway of a series of biomimetic ferric heme superoxide mimics, [(Por)FeIII(O2 -⋅)], in the presence of NO. Therein, our model systems gave rise to three distinct nitroindole products, including 4-nitroindole, the product analogous to that obtained with TxtE. Moreover, 15N and 18O isotope labeling studies, along with meticulously designed control experiments lend credence to a heme peroxynitrite active nitrating agent, drawing close similarities to the tryptophan nitration mechanism of TxtE. All organic and inorganic reaction components have been fully characterized using spectroscopic methods. Theoretical investigation into several mechanistic possibilities deem a unique indolyl radical based reaction pathway as the most energetically favorable, products of which, are in excellent agreement with experimental findings.
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Affiliation(s)
- Pritam Mondal
- Department of Chemistry and Biochemistry, The University of Alabama, Tuscaloosa, AL 35487, United States
- Current address: Department of Chemical Sciences, Indian Institute of Science Education and Research, Mohali, Punjab, 140306, India
| | - Dhilanka Udukalage
- Department of Chemistry and Biochemistry, The University of Alabama, Tuscaloosa, AL 35487, United States
| | - Abubaker A Mohamed
- Manchester Institute of Biotechnology, The University of Manchester, 131 Princess Street, Manchester, M1 7DN, United Kingdom
- Department of Chemical Engineering, The University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom
| | - Henrik P H Wong
- Manchester Institute of Biotechnology, The University of Manchester, 131 Princess Street, Manchester, M1 7DN, United Kingdom
- Department of Chemical Engineering, The University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom
| | - Sam P de Visser
- Manchester Institute of Biotechnology, The University of Manchester, 131 Princess Street, Manchester, M1 7DN, United Kingdom
- Department of Chemical Engineering, The University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom
| | - Gayan B Wijeratne
- Department of Chemistry and Biochemistry, The University of Alabama, Tuscaloosa, AL 35487, United States
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5
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Cao Y, Wong HPH, Warwicker J, Hay S, de Visser SP. What is the Origin of the Regioselective C 3-Hydroxylation of L-Arg by the Nonheme Iron Enzyme Capreomycin C? Chemistry 2024; 30:e202402604. [PMID: 39190221 DOI: 10.1002/chem.202402604] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2024] [Revised: 08/26/2024] [Accepted: 08/27/2024] [Indexed: 08/28/2024]
Abstract
The nonheme iron dioxygenase capreomycin C (CmnC) hydroxylates a free L-arginine amino acid regio- and stereospecifically at the C3-position as part of the capreomycin antibiotics biosynthesis. Little is known on its structure, catalytic cycle and substrate specificity and, therefore, a comprehensive computational study was performed. A large QM cluster model of CmnC was created of 297 atoms and the mechanisms for C3-H, C4-H and C5-H hydroxylation and C3-C4 desaturation were investigated. All low-energy pathways correspond to radical reaction mechanisms with an initial hydrogen atom abstraction followed by OH rebound to form alcohol product complexes. The work is compared to alternative L-Arg hydroxylating nonheme iron dioxygenases and the differences in active site polarity are compared. We show that a tight hydrogen bonding network in the substrate binding pocket positions the substrate in an ideal orientation for C3-H activation, whereby the polar groups in the substrate binding pocket induce an electric field effect that guides the selectivity.
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Affiliation(s)
- Yuanxin Cao
- Manchester Institute of Biotechnology, The University of Manchester, 131 Princess Street, Manchester, M1 7DN, United Kingdom
- Department of Chemistry, The University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom
| | - Henrik P H Wong
- Manchester Institute of Biotechnology, The University of Manchester, 131 Princess Street, Manchester, M1 7DN, United Kingdom
- Department of Chemical Engineering, The University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom
| | - Jim Warwicker
- Manchester Institute of Biotechnology, The University of Manchester, 131 Princess Street, Manchester, M1 7DN, United Kingdom
- School of Biological Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom
| | - Sam Hay
- Manchester Institute of Biotechnology, The University of Manchester, 131 Princess Street, Manchester, M1 7DN, United Kingdom
- Department of Chemistry, The University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom
| | - Sam P de Visser
- Manchester Institute of Biotechnology, The University of Manchester, 131 Princess Street, Manchester, M1 7DN, United Kingdom
- Department of Chemical Engineering, The University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom
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6
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Jana RD, Das A, Samanta R, Banerjee S, Paul S, Paine TK. Stereoelectronic Tuning of Bioinspired Nonheme Iron(IV)-Oxo Species by Amide Groups in Primary and Secondary Coordination Spheres for Selective Oxygenation Reactions. Inorg Chem 2024; 63:21042-21058. [PMID: 39433290 DOI: 10.1021/acs.inorgchem.4c03155] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2024]
Abstract
Two mononuclear iron(II) complexes, [(6-amide2-BPMEN)FeII](OTf)2 (1) and [(6-amide-Me-BPMEN)FeII(OTf)](OTf) (2), supported by two BPMEN-derived (BPMEN = N1,N2-dimethyl-N1,N2-bis(pyridine-2-yl-methyl)ethane-1,2-diamine) ligands bearing one or two amide functionalities have been isolated to study their reactivity in the oxygenation of C-H and C═C bonds using isopropyl 2-iodoxybenzoate (iPr-IBX ester) as the oxidant. Both 1 and 2 contain six-coordinate high-spin iron(II) centers in the solid state and in solution. The 6-amide2-BPMEN ligand stabilizes an S = 1 iron(IV)-oxo intermediate, [(6-amide2-BPMEN)FeIV(O)]2+ (1A). The oxidant (1A) oxygenates the C-H and C═C bonds with a high selectivity. Oxidant 1A, upon treatment with 2,6-lutidine, is transformed into another oxidant [{(6-amide2-BPMEN)-(H)}FeIV(O)]+ (1B) through deprotonation of an amide group, resulting in a stronger equatorial ligand field and subsequent stabilization of the triplet ground state. In contrast, no iron-oxo species could be observed from complex 2 and [(6-Me2-BPMEN)FeII(OTf)2] (3) under similar experimental conditions. The iron(IV)-oxo oxidant 1A shows the highest A/K selectivity in cyclohexane oxidation and 3°/2° selectivity in adamantane oxidation reported for any synthetic nonheme iron(IV)-oxo complexes. Theoretical investigation reveals that the hydrogen bonding interaction between the -NH group of the noncoordinating amide group and Fe═O core smears out the equatorial charge density, reducing the triplet-quintet splitting, and thus helping complex 1A to achieve better reactivity.
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Affiliation(s)
- Rahul Dev Jana
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Kolkata, Jadavpur 700032, India
| | - Abhishek Das
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Kolkata, Jadavpur 700032, India
| | - Rajib Samanta
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Kolkata, Jadavpur 700032, India
| | - Sridhar Banerjee
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Kolkata, Jadavpur 700032, India
| | - Satadal Paul
- Department of Chemistry, Bangabasi Morning College, 19 Rajkumar Chakraborty Sarani, Kolkata 700009, India
| | - Tapan Kanti Paine
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Kolkata, Jadavpur 700032, India
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7
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Goswami S, Gill K, Yin X, Swart M, Garcia-Bosch I. Cu-Promoted ipso-Hydroxylation of sp 2 Bonds with Concomitant Aromatic 1,2-Rearrangement Involving a Cu-oxyl-hydroxo Species. Inorg Chem 2024; 63:20675-20688. [PMID: 39422540 PMCID: PMC11523237 DOI: 10.1021/acs.inorgchem.4c03304] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2024] [Revised: 09/26/2024] [Accepted: 10/02/2024] [Indexed: 10/19/2024]
Abstract
Herein, we report the first example of Cu-promoted β ipso-hydroxylation of substituted benzophenones using a bidentate directing group (DG) and H2O2 as an oxidant. In addition to the new C-O bond formed, the ipso-oxidation induces a very unusual 1,2-rearrangement of the iminyl group to the vicinal γ position. This transformation is highly dependent on the substrate utilized (favored for 4-methoxy-substituted benzophenones) and on the DG used (2-picolylamine leads to selective γ-C-H functionalization, while β ipso-oxidation requires 2-(2-aminoethyl)pyridine). An analysis of the oxidation of substrate-ligands derived from 2-(2-aminoethyl)pyridine and unsymmetrical 4-MeO-substituted benzophenones indicates high regioselectivity (up to 89:11 for the MeO-substituted arene ring and up to 92:8 for β ipso- vs γ-C-H hydroxylation). Mechanistic studies (which include spectroscopic characterization of reaction intermediates, kinetics, and calculations) suggest the formation of a mononuclear CuIIOOH species before the rate-determining step (rds) of the reaction. DFT calculations suggest that the γ-C-H hydroxylation pathway involves a one-step concerted O-O cleavage and electrophilic aromatic attack. Conversely, β ipso-hydroxylation occurs in a stepwise fashion, in which O-O bond cleavage produces a CuIII(O·)(OH) before electrophilic aromatic attack. Calculations also shed light on the mechanism of the 1,2-rearrangement step, which involves strain release from a spiro 5-membered to a 6-membered Cu chelate.
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Affiliation(s)
- Sunipa Goswami
- Department
of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - Karan Gill
- Department
of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - Xinyi Yin
- Department
of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - Marcel Swart
- University
of Girona, Campus Montilivi (Ciències), IQCC, Girona, Spain,
ICREA, Pg. Lluís
Companys 23, 08010 Barcelona, Spain
| | - Isaac Garcia-Bosch
- Department
of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
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8
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Zeng Y, He D, Sun J, Zhang A, Luo H, Pan X. Non-radical oxidation driven by iron-based materials without energy assistance in wastewater treatment. WATER RESEARCH 2024; 264:122255. [PMID: 39153313 DOI: 10.1016/j.watres.2024.122255] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2024] [Revised: 07/22/2024] [Accepted: 08/11/2024] [Indexed: 08/19/2024]
Abstract
Chemical oxidation is extensively utilized to mitigate the impact of organic pollutants in wastewater. The non-radical oxidation driven by iron-based materials is noted for its environmental friendliness and resistance to wastewater matrix, and it is a promising approach for practical wastewater treatment. However, the complexity of heterogeneous systems and the diversity of evolutionary pathways make the mechanisms of non-radical oxidation driven by iron-based materials elusive. This work provides a systematic review of various non-radical oxidation systems driven by iron-based materials, including singlet oxygen (1O2), reactive iron species (RFeS), and interfacial electron transfer. The unique mechanisms by which iron-based materials activate different oxidants (ozone, hydrogen peroxide, persulfate, periodate, and peracetic acid) to produce non-radical oxidation are described. The roles of active sites and the unique structures of iron-based materials in facilitating non-radical oxidation are discussed. Commonly employed identification methods in wastewater treatment are compared, such as quenching, chemical probes, spectroscopy, mass spectrometry, and electrochemical testing. According to the process of iron-based materials driving non-radical oxidation to remove organic pollutants, the driving factors at different stages are summarized. Finally, challenges and countermeasures are proposed in terms of mechanism exploration, detection methods and practical applications of non-radical oxidation driven by iron-based materials. This work provides valuable insights for understanding and developing non-radical oxidation systems.
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Affiliation(s)
- Yifeng Zeng
- College of Environment, Zhejiang University of Technology, Hangzhou 310014, China
| | - Dongqin He
- College of Environment, Zhejiang University of Technology, Hangzhou 310014, China
| | - Jianqiang Sun
- College of Environment, Zhejiang University of Technology, Hangzhou 310014, China
| | - Anping Zhang
- College of Environment, Zhejiang University of Technology, Hangzhou 310014, China
| | - Hongwei Luo
- College of Environment, Zhejiang University of Technology, Hangzhou 310014, China; Shaoxing Research Institute, Zhejiang University of Technology, Shaoxing 312085, China.
| | - Xiangliang Pan
- College of Environment, Zhejiang University of Technology, Hangzhou 310014, China.
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9
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Pagès-Vilà N, Gamba I, Clémancey M, Latour JM, Company A, Costas M. Proton-triggered chemoselective halogenation of aliphatic C-H bonds with nonheme Fe IV-oxo complexes. J Inorg Biochem 2024; 259:112643. [PMID: 38924872 DOI: 10.1016/j.jinorgbio.2024.112643] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2024] [Revised: 05/30/2024] [Accepted: 06/14/2024] [Indexed: 06/28/2024]
Abstract
Halogenation of aliphatic C-H bonds is a chemical transformation performed in nature by mononuclear nonheme iron dependent halogenases. The mechanism involves the formation of an iron(IV)-oxo-chloride species that abstracts the hydrogen atom from the reactive C-H bond to form a carbon-centered radical that selectively reacts with the bound chloride ligand, a process commonly referred to as halide rebound. The factors that determine the halide rebound, as opposed to the reaction with the incipient hydroxide ligand, are not clearly understood and examples of well-defined iron(IV)-oxo-halide compounds competent in C-H halogenation are scarce. In this work we have studied the reactivity of three well-defined iron(IV)-oxo complexes containing variants of the tetradentate 1-(2-pyridylmethyl)-1,4,7-triazacyclononane ligand (Pytacn). Interestingly, these compounds exhibit a change in their chemoselectivity towards the functionalization of C-H bonds under certain conditions: their reaction towards C-H bonds in the presence of a halide anionleads to exclusive oxygenation, while the addition of a superacid results in halogenation. Almost quantitative halogenation of ethylbenzene is observed when using the two systems with more sterically congested ligands and even the chlorination of strong C-H bonds such as those of cyclohexane is performed when a methyl group is present in the sixth position of the pyridine ring of the ligand. Mechanistic studies suggest that both reactions, oxygenation and halogenation, proceed through a common rate determining hydrogen atom transfer step and the presence of the acid dictates the fate of the resulting alkyl radical towards preferential halogenation over oxygenation.
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Affiliation(s)
- Neus Pagès-Vilà
- Institut de Química Computacional i Catàlisi (IQCC), Departament de Química, Universitat de Girona, C/ Maria Aurèlia Capmany 69, 17003 Girona, Catalonia, Spain
| | - Ilaria Gamba
- Institut de Química Computacional i Catàlisi (IQCC), Departament de Química, Universitat de Girona, C/ Maria Aurèlia Capmany 69, 17003 Girona, Catalonia, Spain; Departamento de Química, Facultad de Ciencias, Universidad de La Laguna, Av. Astrofísico Sánchez s/n, 38200 La Laguna, Spain.
| | - Martin Clémancey
- Univ. Grenoble Alpes, CNRS, CEA, IRIG, Laboratoire de Chimie et Biologie des Métaux, F-38000 Grenoble, France
| | - Jean-Marc Latour
- Univ. Grenoble Alpes, CNRS, CEA, IRIG, Laboratoire de Chimie et Biologie des Métaux, F-38000 Grenoble, France
| | - Anna Company
- Institut de Química Computacional i Catàlisi (IQCC), Departament de Química, Universitat de Girona, C/ Maria Aurèlia Capmany 69, 17003 Girona, Catalonia, Spain.
| | - Miquel Costas
- Institut de Química Computacional i Catàlisi (IQCC), Departament de Química, Universitat de Girona, C/ Maria Aurèlia Capmany 69, 17003 Girona, Catalonia, Spain.
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10
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Steube J, Fritsch L, Kruse A, Bokareva OS, Demeshko S, Elgabarty H, Schoch R, Alaraby M, Egold H, Bracht B, Schmitz L, Hohloch S, Kühne TD, Meyer F, Kühn O, Lochbrunner S, Bauer M. Isostructural Series of a Cyclometalated Iron Complex in Three Oxidation States. Inorg Chem 2024; 63:16964-16980. [PMID: 39222251 DOI: 10.1021/acs.inorgchem.4c02576] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/04/2024]
Abstract
An isostructural series of FeII, FeIII, and FeIV complexes [Fe(ImP)2]0/+/2+ utilizing the ImP 1,1'-(1,3-phenylene)bis(3-methyl-1-imidazol-2-ylidene) ligand, combining N-heterocyclic carbenes and cyclometalating functions, is presented. The strong donor motif stabilizes the high-valent FeIV oxidation state yet keeps the FeII oxidation state accessible from the parent FeIII compound. Chemical oxidation of [Fe(ImP)2]+ yields stable [FeIV(ImP)2]2+. In contrast, [FeII(ImP)2]0, obtained by reduction, is highly sensitive toward oxygen. Exhaustive ground state characterization by single-crystal X-ray diffraction, 1H NMR, Mössbauer spectroscopy, temperature-dependent magnetic measurements, a combination of X-ray absorption near edge structure and valence-to-core, as well as core-to-core X-ray emission spectroscopy, complemented by detailed density functional theory (DFT) analysis, reveals that the three complexes [Fe(ImP)2]0/+/2+ can be unequivocally attributed to low-spin d6, d5, and d4 complexes. The excited state landscape of the FeII and FeIV complexes is characterized by short-lived 3MLCT and 3LMCT states, with lifetimes of 5.1 and 1.4 ps, respectively. In the FeII-compound, an energetically low-lying MC state leads to fast deactivation of the MLCT state. The distorted square-pyramidal state, where one carbene is dissociated, can not only relax into the ground state, but also into a singlet dissociated state. Its formation was investigated with time-dependent optical spectroscopy, while insights into its structure were gained by NMR spectroscopy.
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Affiliation(s)
- Jakob Steube
- Institute for Inorganic Chemistry, Paderborn University, 33098 Paderborn, Germany
- Center for Sustainable Systems Design (CSSD), Paderborn University, 33098 Paderborn, Germany
| | - Lorena Fritsch
- Institute for Inorganic Chemistry, Paderborn University, 33098 Paderborn, Germany
- Center for Sustainable Systems Design (CSSD), Paderborn University, 33098 Paderborn, Germany
| | - Ayla Kruse
- Department of Life, Light, and Matter, University of Rostock, 18051 Rostock, Germany
- Institute of Physics, University of Rostock, 18051 Rostock, Germany
| | - Olga S Bokareva
- Institute of Physics, University of Rostock, 18051 Rostock, Germany
| | - Serhiy Demeshko
- Institute of Inorganic Chemistry, University of Göttingen, 37077 Göttingen, Germany
| | - Hossam Elgabarty
- Center for Sustainable Systems Design (CSSD), Paderborn University, 33098 Paderborn, Germany
- Institute for Theoretical Chemistry, Paderborn University, 33098 Paderborn, Germany
| | - Roland Schoch
- Institute for Inorganic Chemistry, Paderborn University, 33098 Paderborn, Germany
- Center for Sustainable Systems Design (CSSD), Paderborn University, 33098 Paderborn, Germany
| | - Mohammad Alaraby
- Center for Sustainable Systems Design (CSSD), Paderborn University, 33098 Paderborn, Germany
- Institute for Theoretical Chemistry, Paderborn University, 33098 Paderborn, Germany
| | - Hans Egold
- Institute for Inorganic Chemistry, Paderborn University, 33098 Paderborn, Germany
| | - Bastian Bracht
- Institute for Inorganic Chemistry, Paderborn University, 33098 Paderborn, Germany
- Center for Sustainable Systems Design (CSSD), Paderborn University, 33098 Paderborn, Germany
| | - Lennart Schmitz
- Institute for Inorganic Chemistry, Paderborn University, 33098 Paderborn, Germany
- Center for Sustainable Systems Design (CSSD), Paderborn University, 33098 Paderborn, Germany
| | - Stephan Hohloch
- Institute for Inorganic Chemistry, Paderborn University, 33098 Paderborn, Germany
| | - Thomas D Kühne
- Center for Sustainable Systems Design (CSSD), Paderborn University, 33098 Paderborn, Germany
- Institute for Theoretical Chemistry, Paderborn University, 33098 Paderborn, Germany
| | - Franc Meyer
- Institute of Inorganic Chemistry, University of Göttingen, 37077 Göttingen, Germany
| | - Oliver Kühn
- Department of Life, Light, and Matter, University of Rostock, 18051 Rostock, Germany
- Institute of Physics, University of Rostock, 18051 Rostock, Germany
| | - Stefan Lochbrunner
- Department of Life, Light, and Matter, University of Rostock, 18051 Rostock, Germany
- Institute of Physics, University of Rostock, 18051 Rostock, Germany
| | - Matthias Bauer
- Institute for Inorganic Chemistry, Paderborn University, 33098 Paderborn, Germany
- Center for Sustainable Systems Design (CSSD), Paderborn University, 33098 Paderborn, Germany
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11
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Rydel-Ciszek K, Sobkowiak A. The [(Bn-tpen)Fe II] 2+ Complex as a Catalyst for the Oxidation of Cyclohexene and Limonene with Dioxygen. Molecules 2024; 29:3755. [PMID: 39202835 PMCID: PMC11357577 DOI: 10.3390/molecules29163755] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2024] [Revised: 08/05/2024] [Accepted: 08/06/2024] [Indexed: 09/03/2024] Open
Abstract
[(Bn-tpen)FeII(MeCN)](ClO4)2, containing the pentadentate Bn-tpen-N-benzyl-N,N',N'-tris(2-pyridylmethyl)-1,2-diaminoethane ligand, was studied in the oxygenation of cyclohexene and limonene using low-pressure dioxygen (0.2 atm air or 1 atm pure O2) in acetonitrile. 2-Cyclohexen-1-one and 2-cyclohexen-1-ol are the main products of cyclohexene oxidations, with cyclohexene oxide as a minor product. Limonene is oxidized to limonene oxide, carvone, and carveol. Other oxidation products such as perillaldehyde and perillyl alcohol are found in trace amounts. This catalyst is slightly less active than the previously reported [(N4Py)FeII(MeCN)](ClO4)2 (N4Py-N,N-bis(2-pyridylmethyl)-N-(bis-2-pyridylmethyl)amine). Based on cyclic voltammetry experiments, it is postulated that [(Bn-tpen)FeIV=O]2+ is the active species. The induction period of approx. 3 h during cyclohexene oxygenation is probably caused by deactivation of the reactive Fe(IV)=O species by the parent Fe(II) complex. Equimolar mixtures of Fe(II) salt and the ligand (in situ-formed catalyst) gave catalytic performance similar to that of the synthesized catalyst.
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Affiliation(s)
- Katarzyna Rydel-Ciszek
- Department of Physical Chemistry, Faculty of Chemistry, Rzeszów University of Technology, Al. Powstańców Warszawy 6, 35-959 Rzeszów, Poland
| | - Andrzej Sobkowiak
- Department of Physical Chemistry, Faculty of Chemistry, Rzeszów University of Technology, Al. Powstańców Warszawy 6, 35-959 Rzeszów, Poland
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12
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Bhardwaj A, Mondal B. Unraveling the Geometry-Driven C═C Epoxidation and C-H Hydroxylation Reactivity of Tetra-Coordinated Nonheme Iron(IV)-Oxo Complexes. Inorg Chem 2024; 63:14468-14481. [PMID: 39030661 DOI: 10.1021/acs.inorgchem.4c01708] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/21/2024]
Abstract
The electronic structure and reactivity of tetra-coordinated nonheme iron(IV)-oxo complexes have remained unexplored for years. The recent synthesis of a closed-shell iron(IV)-oxo complex [(quinisox)FeIV(O)]+ (1) has set up a platform to understand how such complexes compare with the celebrated open-shell iron-oxo chemistry. Herein, using density functional theory and ab initio calculations, we present an in-depth electronic structure investigation of the C═C epoxidation [oxygen atom transfer (OAT)] and C-H hydroxylation [hydrogen atom transfer (HAT)] reactivity of 1. Using a solvent-coordinated geometry of 1 (1') and other potential tetra-coordinated iron(IV)-oxo complexes bearing rigid ligands (2 and 3), we established the geometric origin of spin-state energetics and reactivity of 1. Complex 1 featuring a strong Fe-O bond exhibits OAT and HAT reactivity in its quintet state. The lowest quintet OAT pathway has a lower barrier by ∼4 kcal/mol than the quintet HAT pathway, corroborating the experimentally observed gas-phase OAT reactivity preference. A conventional HAT reactivity preference for 2 and a comparable OAT and HAT reactivity for 3 are observed. This further supports the geometry-driven reactivity preference for 1. Noncovalent interaction analyses reveal a pronounced π-π interaction between the substrate and ligand in the OAT transition state, rationalizing the origin of the observed reactivity preference for 1.
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Affiliation(s)
- Akhil Bhardwaj
- School of Chemical Sciences, Indian Institute of Technology Mandi, Mandi, Himachal Pradesh 175075, India
| | - Bhaskar Mondal
- School of Chemical Sciences, Indian Institute of Technology Mandi, Mandi, Himachal Pradesh 175075, India
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13
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Kim S, Lee Y, Tripodi GL, Roithová J, Lee S, Cho J. Controlling Reactivity through Spin Manipulation: Steric Bulkiness of Peroxocobalt(III) Complexes. J Am Chem Soc 2024. [PMID: 39031334 DOI: 10.1021/jacs.4c03211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/22/2024]
Abstract
The intrinsic relationship between spin states and reactivity in peroxocobalt(III) complexes was investigated, specifically focusing on the influence of steric modulation on supporting ligands. Together with the previously reported [CoIII(TBDAP)(O2)]+ (2Tb), which exhibits spin crossover characteristics, two peroxocobalt(III) complexes, [CoIII(MDAP)(O2)]+ (2Me) and [CoIII(ADDAP)(O2)]+ (2Ad), bearing pyridinophane ligands with distinct N-substituents such as methyl and adamantyl groups, were synthesized and characterized. By manipulating the steric bulkiness of the N-substituents, control of spin states in peroxocobalt(III) complexes was demonstrated through various physicochemical analyses. Notably, 2Ad oxidized the nitriles to generate hydroximatocobalt(III) complexes, while 2Me displayed an inability for such oxidation reactions. Furthermore, both 2Ad and 2Tb exhibited similarities in spectroscopic and geometric features, demonstrating spin crossover behavior between S = 0 and S = 1. The steric bulkiness of the adamantyl and tert-butyl group on the axial amines was attributed to inducing a weak ligand field on the cobalt(III) center. Thus, 2Ad and 2Tb are an S = 1 state under the reaction conditions. In contrast, the less bulky methyl group on the amines of 2Me resulted in an S = 0 state. The redox potential of the peroxocobalt(III) complexes was also influenced by the ligand field arising from the steric bulkiness of the N-substituents in the order of 2Me (-0.01 V) < 2Tb (0.29 V) = 2Ad (0.29 V). Theoretical calculations using DFT supported the experimental observations, providing insights into the electronic structure and emphasizing the importance of the spin state of peroxocobalt(III) complexes in nitrile activation.
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Affiliation(s)
- Seonghan Kim
- Department of Chemistry, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Korea
- Department of Emerging Materials Science, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 42988, Korea
| | - Yuri Lee
- Department of Chemistry, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Korea
| | - Guilherme L Tripodi
- Department of Spectroscopy and Catalysis, Institute for Molecules and Materials, Radboud University Nijmegen, Nijmegen 6525 AJ, The Netherlands
| | - Jana Roithová
- Department of Spectroscopy and Catalysis, Institute for Molecules and Materials, Radboud University Nijmegen, Nijmegen 6525 AJ, The Netherlands
| | - Sunggi Lee
- Department of Emerging Materials Science, Daegu Gyeongbuk Institute of Science and Technology (DGIST), Daegu 42988, Korea
| | - Jaeheung Cho
- Department of Chemistry, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Korea
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14
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Tian YC, Zhang P, Lin KT, Fu CW, Ye S, Lee WZ. A Mechanistic Spectrum of O-H Bond Cleavage Observed for Reactions of Phenols with a Manganese Superoxo Complex. Chemistry 2024; 30:e202401826. [PMID: 38747420 DOI: 10.1002/chem.202401826] [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: 05/09/2024] [Indexed: 05/30/2024]
Abstract
Reaction of a rare and well-characterized MnIII-superoxo species, Mn(BDPBrP)(O2⋅) (1, H2BDPBrP=2,6-bis((2-(S)-di(4-bromo)phenylhydroxylmethyl-1-pyrrolidinyl)methyl)pyridine), with 4-dimethylaminophenol at -80 °C proceeds via concerted proton electron transfer (CPET) to produce a MnIII-hydroperoxo complex, Mn(BDPBrP)(OOH) (2), alongside 4-dimethylaminophenoxy radical; whereas, upon treatment with 4-nitrophenol, complex 1 undergoes a proton transfer process to afford a MnIV-hydroperoxo complex, [Mn(BDPBrP)(OOH)]+ (3). Intriguingly, the reactions of 1 with 4-chlorophenol and 4-methoxyphenol follow two routes of CPET and sequential proton and electron transfer to furnish complex 2 in the end. UV-vis and EPR spectroscopic studies coupled with DFT calculations provided support for this wide mechanistic spectrum of activating various phenol O-H bonds by a single MnIII-superoxo complex, 1.
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Affiliation(s)
- Yao-Cheng Tian
- Department of Chemistry, National Taiwan Normal University, 11677, Taipei, Taiwan
| | - Peng Zhang
- State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 116023, Dalian, China
- University of Chinese Academy of Sciences, 100049, Beijing, China
| | - Kuan-Ting Lin
- Department of Chemistry, National Taiwan Normal University, 11677, Taipei, Taiwan
| | - Chung-Wei Fu
- Department of Chemistry, National Taiwan Normal University, 11677, Taipei, Taiwan
| | - Shengfa Ye
- State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 116023, Dalian, China
| | - Way-Zen Lee
- Department of Chemistry, National Taiwan Normal University, 11677, Taipei, Taiwan
- Department of Medicinal and Applied Chemistry, Kaohsiung Medical University, 807, Kaohsiung, Taiwan
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15
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Fagnano A, Frateloreto F, Paoloni R, Sappino C, Lanzalunga O, Costas M, Di Stefano S, Olivo G. Proximity Effects on the Reactivity of a Nonheme Iron (IV) Oxo Complex in C-H Oxidation. Angew Chem Int Ed Engl 2024; 63:e202401694. [PMID: 38478739 DOI: 10.1002/anie.202401694] [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: 01/24/2024] [Indexed: 04/05/2024]
Abstract
Precise control of substrate positioning and orientation (its proximity to the reactive unit) is often invoked to rationalize the superior enzymatic reaction rates and selectivities when compared to synthetic models. Artificial nonheme iron (IV) oxo (Fe(IV)=O) complexes react with C(sp3)-H bonds via a biomimetic Hydrogen Atom Transfer/Hydroxyl Rebound mechanism, but rates, site-selectivity and even hydroxyl rebound efficiency (ligand rebound versus substrate radical diffusion) are smaller than in oxygenases. Herein, we quantitatively analyze how substrate binding modulates nonheme Fe(IV)=O reactivity by comparing rates and outcomes of C-H oxidation by a pair of Fe(IV)=O complexes that share the same first coordination sphere but only one contains a crown ether receptor that recognizes the substrate. Substrate binding makes the reaction intramolecular, exhibiting Michaelis-Menten kinetics and increased reaction rates. In addition, C-H oxidation occurs with high site selectivity for remote sites. Analysis of Effective Molarity reveals that the system operates at its maximal theoretical capability for the oxidation of these remote sites. Remarkably, substrate positioning also affects Hydroxyl Rebound, whose efficiency only increases on the sites placed in proximity by recognition. Overall, these observations provide evidence that supramolecular control of substrate positioning can effectively modulate the reactivity of oxygenases and its models.
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Affiliation(s)
- Alessandro Fagnano
- Dipartimento di Chimica and Istituto CNR per i Sistemi Biologici (ISB-CNR), Sezione Meccanismi di Reazione, c/o Dipartimento di Chimica, Università di Roma "La Sapienza", P.le A. Moro, 5 I-00185, Rome, Italy
| | - Federico Frateloreto
- Dipartimento di Chimica and Istituto CNR per i Sistemi Biologici (ISB-CNR), Sezione Meccanismi di Reazione, c/o Dipartimento di Chimica, Università di Roma "La Sapienza", P.le A. Moro, 5 I-00185, Rome, Italy
| | - Roberta Paoloni
- Dipartimento di Chimica and Istituto CNR per i Sistemi Biologici (ISB-CNR), Sezione Meccanismi di Reazione, c/o Dipartimento di Chimica, Università di Roma "La Sapienza", P.le A. Moro, 5 I-00185, Rome, Italy
| | - Carla Sappino
- Dipartimento di Chimica and Istituto CNR per i Sistemi Biologici (ISB-CNR), Sezione Meccanismi di Reazione, c/o Dipartimento di Chimica, Università di Roma "La Sapienza", P.le A. Moro, 5 I-00185, Rome, Italy
| | - Osvaldo Lanzalunga
- Dipartimento di Chimica and Istituto CNR per i Sistemi Biologici (ISB-CNR), Sezione Meccanismi di Reazione, c/o Dipartimento di Chimica, Università di Roma "La Sapienza", P.le A. Moro, 5 I-00185, Rome, Italy
| | - Miquel Costas
- QBIS-Cat, Institut de Química Computacional i Catàlisi (IQCC), Departament de Quimica, Universitat de Girona Campus Montilivi, 17071, Girona, Catalonia, Spain
| | - Stefano Di Stefano
- Dipartimento di Chimica and Istituto CNR per i Sistemi Biologici (ISB-CNR), Sezione Meccanismi di Reazione, c/o Dipartimento di Chimica, Università di Roma "La Sapienza", P.le A. Moro, 5 I-00185, Rome, Italy
| | - Giorgio Olivo
- Dipartimento di Chimica and Istituto CNR per i Sistemi Biologici (ISB-CNR), Sezione Meccanismi di Reazione, c/o Dipartimento di Chimica, Università di Roma "La Sapienza", P.le A. Moro, 5 I-00185, Rome, Italy
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16
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Thomas J, Mokkawes T, Senft L, Dey A, Gordon JB, Ivanovic-Burmazovic I, de Visser SP, Goldberg DP. Axial Ligation Impedes Proton-Coupled Electron-Transfer Reactivity of a Synthetic Compound-I Analogue. J Am Chem Soc 2024; 146:12338-12354. [PMID: 38669456 PMCID: PMC11305010 DOI: 10.1021/jacs.3c08950] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/28/2024]
Abstract
The nature of the axial ligand in high-valent iron-oxo heme enzyme intermediates and related synthetic catalysts is a critical structural element for controlling proton-coupled electron-transfer (PCET) reactivity of these species. Herein, we describe the generation and characterization of three new 6-coordinate, iron(IV)-oxo porphyrinoid-π-cation-radical complexes and report their PCET reactivity together with a previously published 5-coordinate analogue, FeIV(O)(TBP8Cz+•) (TBP8Cz = octakis(p-tert-butylphenyl)corrolazinato3-) (2) (Cho, K. A high-valent iron-oxo corrolazine activates C-H bonds via hydrogen-atom transfer. J. Am. Chem. Soc. 2012, 134, 7392-7399). The new complexes FeIV(O)(TBP8Cz+•)(L) (L = 1-methyl imidazole (1-MeIm) (4a), 4-dimethylaminopyridine (DMAP) (4b), cyanide (CN-)(4c)) can be generated from either oxidation of the ferric precursors or by addition of L to the Compound-I (Cpd-I) analogue at low temperatures. These complexes were characterized by UV-vis, electron paramagnetic resonance (EPR), and Mössbauer spectroscopies, and cryospray ionization mass spectrometry (CSI-MS). Kinetic studies using 4-OMe-TEMPOH as a test substrate indicate that coordination of a sixth axial ligand dramatically lowers the PCET reactivity of the Cpd-I analogue (rates up to 7000 times slower). Extensive density functional theory (DFT) calculations together with the experimental data show that the trend in reactivity with the axial ligands does not correlate with the thermodynamic driving force for these reactions or the calculated strengths of the O-H bonds being formed in the FeIV(O-H) products, pointing to non-Bell-Evans-Polanyi behavior. However, the PCET reactivity does follow a trend with the bracketed reduction potential of Cpd-I analogues and calculated electron affinities. The combined data suggest a concerted mechanism (a concerted proton electron transfer (CPET)) and an asynchronous movement of the electron/proton pair in the transition state.
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Affiliation(s)
- Jithin Thomas
- Department of Chemistry, The Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States
| | - Thirakorn Mokkawes
- The Manchester Institute of Biotechnology and Department of Chemical Engineering, The University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom
| | - Laura Senft
- Department Chemie, Ludwig-Maximilians-Universität München, Butenandtstr., 5-13, Haus D, 81377 München, Germany
| | - Aniruddha Dey
- Department of Chemistry, The Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States
| | - Jesse B Gordon
- Department of Chemistry, The Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States
| | - Ivana Ivanovic-Burmazovic
- Department Chemie, Ludwig-Maximilians-Universität München, Butenandtstr., 5-13, Haus D, 81377 München, Germany
| | - Sam P de Visser
- The Manchester Institute of Biotechnology and Department of Chemical Engineering, The University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom
| | - David P Goldberg
- Department of Chemistry, The Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, United States
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17
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Gong Z, Wang L, Xu Y, Xie D, Qi X, Nam W, Guo M. Enhanced Reactivities of Iron(IV)-Oxo Porphyrin Species in Oxidation Reactions Promoted by Intramolecular Hydrogen-Bonding. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2024; 11:e2310333. [PMID: 38477431 PMCID: PMC11109629 DOI: 10.1002/advs.202310333] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2023] [Revised: 02/19/2024] [Indexed: 03/14/2024]
Abstract
High-valent iron-oxo species are one of the common intermediates in both biological and biomimetic catalytic oxidation reactions. Recently, hydrogen-bonding (H-bonding) has been proved to be critical in determining the selectivity and reactivity. However, few examples have been established for mechanistic insights into the H-bonding effect. Moreover, intramolecular H-bonding effect on both C-H activation and oxygen atom transfer (OAT) reactions in synthetic porphyrin model system has not been investigated yet. In this study, a series of heme-containing iron(IV)-oxo porphyrin species with or without intramolecular H-bonding are synthesized and characterized. Kinetic studies revealed that intramolecular H-bonding can significantly enhance the reactivity of iron(IV)-oxo species in OAT, C-H activation, and electron-transfer reactions. This unprecedented unified H-bonding effect is elucidated by theoretical calculations, which showed that intramolecular H-bonding interactions lower the energy of the anti-bonding orbital of iron(IV)-oxo porphyrin species, resulting in the enhanced reactivities in oxidation reactions irrespective of the reaction type. To the best of the knowledge, this is the first extensive investigation on the intramolecular H-bonding effect in heme system. The results show that H-bonding interactions have a unified effect with iron(IV)-oxo porphyrin species in all three investigated reactions.
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Affiliation(s)
- Zhe Gong
- College of Chemistry and Molecular SciencesWuhan UniversityWuhanHubei430072P. R. China
| | - Liwei Wang
- College of Chemistry and Molecular SciencesWuhan UniversityWuhanHubei430072P. R. China
| | - Yiran Xu
- College of Chemistry and Molecular SciencesWuhan UniversityWuhanHubei430072P. R. China
| | - Duanfeng Xie
- College of Chemistry and Molecular SciencesWuhan UniversityWuhanHubei430072P. R. China
| | - Xiaotian Qi
- College of Chemistry and Molecular SciencesWuhan UniversityWuhanHubei430072P. R. China
| | - Wonwoo Nam
- Department of Chemistry and Nano ScienceEwha Womans UniversitySeoul03760South Korea
| | - Mian Guo
- College of Chemistry and Molecular SciencesWuhan UniversityWuhanHubei430072P. R. China
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18
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Cao Y, Hay S, de Visser SP. An Active Site Tyr Residue Guides the Regioselectivity of Lysine Hydroxylation by Nonheme Iron Lysine-4-hydroxylase Enzymes through Proton-Coupled Electron Transfer. J Am Chem Soc 2024; 146:11726-11739. [PMID: 38636166 PMCID: PMC11066847 DOI: 10.1021/jacs.3c14574] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2023] [Revised: 04/05/2024] [Accepted: 04/05/2024] [Indexed: 04/20/2024]
Abstract
Lysine dioxygenase (KDO) is an important enzyme in human physiology involved in bioprocesses that trigger collagen cross-linking and blood pressure control. There are several KDOs in nature; however, little is known about the factors that govern the regio- and stereoselectivity of these enzymes. To understand how KDOs can selectively hydroxylate their substrate, we did a comprehensive computational study into the mechanisms and features of 4-lysine dioxygenase. In particular, we selected a snapshot from the MD simulation on KDO5 and created large QM cluster models (A, B, and C) containing 297, 312, and 407 atoms, respectively. The largest model predicts regioselectivity that matches experimental observation with rate-determining hydrogen atom abstraction from the C4-H position, followed by fast OH rebound to form 4-hydroxylysine products. The calculations show that in model C, the dipole moment is positioned along the C4-H bond of the substrate and, therefore, the electrostatic and electric field perturbations of the protein assist the enzyme in creating C4-H hydroxylation selectivity. Furthermore, an active site Tyr233 residue is identified that reacts through proton-coupled electron transfer akin to the axial Trp residue in cytochrome c peroxidase. Thus, upon formation of the iron(IV)-oxo species in the catalytic cycle, the Tyr233 phenol loses a proton to the nearby Asp179 residue, while at the same time, an electron is transferred to the iron to create an iron(III)-oxo active species. This charged tyrosyl residue directs the dipole moment along the C4-H bond of the substrate and guides the selectivity to the C4-hydroxylation of the substrate.
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Affiliation(s)
- Yuanxin Cao
- Manchester
Institute of Biotechnology, The University
of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom
- Department
of Chemistry, The University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
| | - Sam Hay
- Manchester
Institute of Biotechnology, The University
of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom
- Department
of Chemistry, The University of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
| | - Sam P. de Visser
- Manchester
Institute of Biotechnology, The University
of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom
- Department
of Chemical Engineering, The University
of Manchester, Oxford Road, Manchester M13 9PL, United Kingdom
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19
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Ali HS, de Visser SP. QM/MM Study Into the Mechanism of Oxidative C=C Double Bond Cleavage by Lignostilbene-α,β-Dioxygenase. Chemistry 2024; 30:e202304172. [PMID: 38373118 DOI: 10.1002/chem.202304172] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2023] [Revised: 01/29/2024] [Accepted: 02/19/2024] [Indexed: 02/21/2024]
Abstract
The enzymatic biosynthesis of fragrance molecules from lignin fragments is an important reaction in biotechnology for the sustainable production of fine chemicals. In this work we investigated the biosynthesis of vanillin from lignostilbene by a nonheme iron dioxygenase using QM/MM and tested several suggested proposals via either an epoxide or dioxetane intermediate. Binding of dioxygen to the active site of the protein results in the formation of an iron(II)-superoxo species with lignostilbene cation radical. The dioxygenase mechanism starts with electrophilic attack of the terminal oxygen atom of the superoxo group on the central C=C bond of lignostilbene, and the second-coordination sphere effects in the substrate binding pocket guide the reaction towards dioxetane formation. The computed mechanism is rationalized with thermochemical cycles and valence bond schemes that explain the electron transfer processes during the reaction mechanism. Particularly, the polarity of the protein and the local electric field and dipole moments enable a facile electron transfer and an exergonic dioxetane formation pathway.
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Affiliation(s)
- Hafiz Saqib Ali
- Manchester Institute of Biotechnology, The University of Manchester, 131 Princess Street, Manchester, M1 7DN, United Kingdom
- Department of Chemical Engineering, The University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom
| | - Sam P de Visser
- Manchester Institute of Biotechnology, The University of Manchester, 131 Princess Street, Manchester, M1 7DN, United Kingdom
- Department of Chemical Engineering, The University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom
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20
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Sarkar W, LaDuca A, Wilson JR, Szymczak NK. Iron-Catalyzed C-H Oxygenation Using Perchlorate Enabled by Secondary Sphere Hydrogen Bonds. J Am Chem Soc 2024; 146:10508-10516. [PMID: 38564312 PMCID: PMC11137739 DOI: 10.1021/jacs.3c14433] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/04/2024]
Abstract
Perchlorate (ClO4-) is a groundwater pollutant that is challenging to remediate. We report a strategy to use Fe(II) tris(2-pyridylmethyl)amine (TPA) complexes featuring appended aniline hydrogen bonds (H-bonds) to promote ClO4- reduction. These complexes facilitate oxygen atom transfer from ClO4- to PPh3 and C-H oxygenation reactions of organic substrates. Catalytic reactions using 15 mol % afforded excellent yields for oxygenation of anthracene and cyclic alkyl aromatics, and this methodology tolerates aryl halides as well as heterocycles containing either O, S, or N.
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Affiliation(s)
- Writhabrata Sarkar
- Department of Chemistry, University of Michigan, 930 N. University, Ann Arbor, Michigan 48109, United States
| | - Andrew LaDuca
- Department of Chemistry, University of Michigan, 930 N. University, Ann Arbor, Michigan 48109, United States
| | - Jessica R Wilson
- Department of Chemistry, University of Michigan, 930 N. University, Ann Arbor, Michigan 48109, United States
| | - Nathaniel K Szymczak
- Department of Chemistry, University of Michigan, 930 N. University, Ann Arbor, Michigan 48109, United States
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21
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Yamada Y, Miwa Y, Toyoda Y, Uno Y, Phung QM, Tanaka K. Effect of porphyrin ligands on the catalytic CH 4 oxidation activity of monocationic μ-nitrido-bridged iron porphyrinoid dimers by using H 2O 2 as an oxidant. Dalton Trans 2024; 53:6556-6567. [PMID: 38525694 DOI: 10.1039/d3dt04313d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/26/2024]
Abstract
The μ-nitrido-bridged iron phthalocyanine homodimer is a potent molecule-based CH4 oxidation catalyst that can effectively oxidize chemically stable CH4 under mild reaction conditions in an acidic aqueous solution including an oxidant such as H2O2. The reactive intermediate is a high-valent iron-oxo species generated upon reaction with H2O2. However, a detailed comparison of the CH4 oxidation activity of the μ-nitrido-bridged iron phthalocyanine dimer with those of μ-nitrido-bridged iron porphyrinoid dimers containing one or two porphyrin ring(s) has not been yet reported, although porphyrins are the most important class of porphyrinoids. Herein, we compare the catalytic CH4 and CH3CH3 oxidation activities of a monocationic μ-nitrido-bridged iron porphyrin homodimer and a monocationic μ-nitrido-bridged heterodimer of an iron porphyrin and an iron phthalocyanine with those of a monocationic μ-nitrido-bridged iron phthalocyanine homodimer in an acidic aqueous solution containing H2O2 as an oxidant. It was demonstrated that the CH4 oxidation activities of monocationic μ-nitrido-bridged iron porphyrinoid dimers containing porphyrin ring(s) were much lower than that of a monocationic μ-nitrido-bridged iron phthalocyanine homodimer. These findings suggested that the difference in the electronic structure of the porphyrinoid rings of monocationic μ-nitrido-bridged iron porphyrinoid dimers strongly affected their catalytic light alkane oxidation activities.
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Affiliation(s)
- Yasuyuki Yamada
- Department of Chemistry, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan.
- Research Center for Materials Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
| | - Yusuke Miwa
- Department of Chemistry, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan.
| | - Yuka Toyoda
- Research Center for Materials Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
| | - Yoshiki Uno
- Department of Chemistry, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan.
| | - Quan Manh Phung
- Department of Chemistry, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan.
- Institute of Transformaytive Bio-Molecules (ITBM), Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
| | - Kentaro Tanaka
- Department of Chemistry, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan.
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22
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Hardy FG, Wong HPH, de Visser SP. Computational Study Into the Oxidative Ring-Closure Mechanism During the Biosynthesis of Deoxypodophyllotoxin. Chemistry 2024; 30:e202400019. [PMID: 38323740 DOI: 10.1002/chem.202400019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2024] [Revised: 02/01/2024] [Accepted: 02/07/2024] [Indexed: 02/08/2024]
Abstract
The nonheme iron dioxygenase deoxypodophyllotoxin synthase performs an oxidative ring-closure reaction as part of natural product synthesis in plants. How the enzyme enables the oxidative ring-closure reaction of (-)-yatein and avoids substrate hydroxylation remains unknown. To gain insight into the reaction mechanism and understand the details of the pathways leading to products and by-products we performed a comprehensive computational study. The work shows that substrate is bound tightly into the substrate binding pocket with the C7'-H bond closest to the iron(IV)-oxo species. The reaction proceeds through a radical mechanism starting with hydrogen atom abstraction from the C7'-H position followed by ring-closure and a final hydrogen transfer to form iron(II)-water and deoxypodophyllotoxin. Alternative mechanisms including substrate hydroxylation and an electron transfer pathway were explored but found to be higher in energy. The mechanism is guided by electrostatic perturbations of charged residues in the second-coordination sphere that prevent alternative pathways.
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Affiliation(s)
- Fintan G Hardy
- Manchester Institute of Biotechnology, The University of Manchester, 131 Princess Street, Manchester, M1 7DN, United Kingdom
- Department of Chemical Engineering, The University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom
| | - Henrik P H Wong
- Manchester Institute of Biotechnology, The University of Manchester, 131 Princess Street, Manchester, M1 7DN, United Kingdom
- Department of Chemical Engineering, The University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom
| | - Sam P de Visser
- Manchester Institute of Biotechnology, The University of Manchester, 131 Princess Street, Manchester, M1 7DN, United Kingdom
- Department of Chemical Engineering, The University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom
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23
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Satpathy JK, Yadav R, Bagha UK, Kumar D, Sastri CV, de Visser SP. Enhanced Reactivity through Equatorial Sulfur Coordination in Nonheme Iron(IV)-Oxo Complexes: Insights from Experiment and Theory. Inorg Chem 2024; 63:6752-6766. [PMID: 38551622 DOI: 10.1021/acs.inorgchem.4c00070] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/16/2024]
Abstract
Sulfur ligation in metalloenzymes often gives the active site unique properties, whether it is the axial cysteinate ligand in the cytochrome P450s or the equatorial sulfur/thiol ligation in nonheme iron enzymes. To understand sulfur ligation to iron complexes and how it affects the structural, spectroscopic, and intrinsic properties of the active species and the catalysis of substrates, we pursued a systematic study and compared sulfur with amine-ligated iron(IV)-oxo complexes. We synthesized and characterized a biomimetic N4S-ligated iron(IV)-oxo complex and compared the obtained results with an analogous N5-ligated iron(IV)-oxo complex. Our work shows that the amine for sulfur replacement in the equatorial ligand framework leads to a rate enhancement for oxygen atom and hydrogen atom transfer reactions. Moreover, the sulfur-ligated iron(IV)-oxo complex reacts through a different reaction mechanism as compared to the N5-ligated iron(IV)-oxo complex, where the former reacts through hydride transfer with the latter reacting via radical pathways. We show that the reactivity differences are caused by a dramatic change in redox potential between the two complexes. Our studies highlight the importance of implementing a sulfur ligand into the equatorial ligand framework of nonheme iron(IV)-oxo complexes and how it affects the physicochemical properties of the oxidant and its reactivity.
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Affiliation(s)
- Jagnyesh K Satpathy
- Department of Chemistry, Indian Institute of Technology, Guwahati 781039, Assam, India
| | - Rolly Yadav
- 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
| | - Devesh Kumar
- Department of Applied Physics, Babasaheb Bhimrao Ambedkar University, School for Physical Sciences, Vidya Vihar, Rae Bareilly Road, Lucknow 226025, UP, India
| | - 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
- The Manchester Institute of Biotechnology and Department of Chemical Engineering, The University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom
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24
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Sahoo S, Harfmann B, Bhatia H, Singh H, Balijapelly S, Choudhury A, Stavropoulos P. A Comparative Study of Cationic Copper(I) Reagents Supported by Bipodal Tetramethylguanidinyl-Containing Ligands as Nitrene-Transfer Catalysts. ACS OMEGA 2024; 9:15697-15708. [PMID: 38585072 PMCID: PMC10993379 DOI: 10.1021/acsomega.4c00909] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/28/2024] [Revised: 03/02/2024] [Accepted: 03/07/2024] [Indexed: 04/09/2024]
Abstract
The bipodal compounds [(TMG2biphenN-R)CuI-NCMe](PF6) (R = Me, Ar (4-CF3Ph-)) and [(TMG2biphenN-Me)CuI-I] have been synthesized with ligands that feature a diarylmethyl- and triaryl-amine framework and superbasic tetramethylguanidinyl residues (TMG). The cationic Cu(I) sites mediate catalytic nitrene-transfer reactions between the imidoiodinane PhI = NTs (Ts = tosyl) and a panel of styrenes in MeCN, to afford aziridines, demonstrating comparable reactivity profiles. The copper reagents have been further explored to execute C-H amination reactions with a variety of aliphatic and aromatic hydrocarbons and two distinct nitrene sources PhI = NTs and PhI = NTces (Tces = 2,2,2-trichloroethylsulfamate) in benzene/HFIP (10:2 v/v). Good yields have been obtained for sec-benzylic and tert-C-H bonds of various substrates, especially with the more electron-deficient catalyst [(TMG2biphenN-Ar)CuI-NCMe](PF6). In conjunction with earlier studies, the order of reactivity of these bipodal cationic reagents as a function of the metal employed is established as Cu > Fe > Co ≥ Mn. However, as opposed to the base-metal analogues, the bipodal Cu reagents are less reactive than a similar tripodal Cu catalyst. The observed fluorophilicity of the bipodal Cu compounds may provide a deactivation pathway.
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Affiliation(s)
- Suraj
Kumar Sahoo
- Department
of Chemistry, Missouri University of Science
and Technology, Rolla, Missouri 65409, United States
| | - Brent Harfmann
- Department
of Chemistry, Missouri University of Science
and Technology, Rolla, Missouri 65409, United States
| | - Himanshu Bhatia
- Department
of Chemistry, Missouri University of Science
and Technology, Rolla, Missouri 65409, United States
| | - Harish Singh
- Department
of Chemistry, Missouri University of Science
and Technology, Rolla, Missouri 65409, United States
| | - Srikanth Balijapelly
- Department
of Chemistry, Missouri University of Science
and Technology, Rolla, Missouri 65409, United States
| | - Amitava Choudhury
- Department
of Chemistry, Missouri University of Science
and Technology, Rolla, Missouri 65409, United States
| | - Pericles Stavropoulos
- Department
of Chemistry, Missouri University of Science
and Technology, Rolla, Missouri 65409, United States
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25
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Keilwerth M, Mao W, Malischewski M, Jannuzzi SAV, Breitwieser K, Heinemann FW, Scheurer A, DeBeer S, Munz D, Bill E, Meyer K. The synthesis and characterization of an iron(VII) nitrido complex. Nat Chem 2024; 16:514-520. [PMID: 38291260 PMCID: PMC10997499 DOI: 10.1038/s41557-023-01418-4] [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: 08/18/2023] [Accepted: 12/08/2023] [Indexed: 02/01/2024]
Abstract
Complexes of iron in high oxidation states are captivating research subjects due to their pivotal role as active intermediates in numerous catalytic processes. Structural and spectroscopic studies of well-defined model complexes often provide evidence of these intermediates. In addition to the fundamental molecular and electronic structure insights gained by these complexes, their reactivity also affects our understanding of catalytic reaction mechanisms for small molecule and bond-activation chemistry. Here, we report the synthesis, structural and spectroscopic characterization of a stable, octahedral Fe(VI) nitrido complex and an authenticated, unique Fe(VII) species, prepared by one-electron oxidation. The super-oxidized Fe(VII) nitride rearranges to an Fe(V) imide through an intramolecular amination mechanism and ligand exchange, which is characterized spectroscopically and computationally. This enables combined reactivity and stability studies on a single molecular system of a rare high-valent complex redox pair. Quantum chemical calculations complement the spectroscopic parameters and provide evidence for a diamagnetic (S = 0) d 2 Fe(VI) and a genuine S = 1/2, d 1 Fe(VII) configuration of these super-oxidized nitrido complexes.
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Affiliation(s)
- Martin Keilwerth
- Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Department of Chemistry and Pharmacy, Inorganic Chemistry, Erlangen, Germany
| | - Weiqing Mao
- Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Department of Chemistry and Pharmacy, Inorganic Chemistry, Erlangen, Germany
| | - Moritz Malischewski
- Freie Universität Berlin, Institute of Chemistry and Biochemistry, Inorganic Chemistry, Berlin, Germany
| | - Sergio A V Jannuzzi
- Max Planck Institute for Chemical Energy Conversion, Mülheim an der Ruhr, Germany
| | - Kevin Breitwieser
- Saarland University, Inorganic Chemistry, Coordination Chemistry, Saarbrücken, Germany
| | - Frank W Heinemann
- Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Department of Chemistry and Pharmacy, Inorganic Chemistry, Erlangen, Germany
| | - Andreas Scheurer
- Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Department of Chemistry and Pharmacy, Inorganic Chemistry, Erlangen, Germany
| | - Serena DeBeer
- Max Planck Institute for Chemical Energy Conversion, Mülheim an der Ruhr, Germany.
| | - Dominik Munz
- Saarland University, Inorganic Chemistry, Coordination Chemistry, Saarbrücken, Germany.
| | - Eckhard Bill
- Max Planck Institute for Chemical Energy Conversion, Mülheim an der Ruhr, Germany
| | - Karsten Meyer
- Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Department of Chemistry and Pharmacy, Inorganic Chemistry, Erlangen, Germany.
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26
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Fiedler AT, Devkota L. Lifting iron higher and higher. Nat Chem 2024; 16:481-482. [PMID: 38548885 DOI: 10.1038/s41557-024-01484-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/07/2024]
Affiliation(s)
- Adam T Fiedler
- Department of Chemistry, Marquette University, Milwaukee, WI, USA.
| | - Laxmi Devkota
- Department of Chemistry, Marquette University, Milwaukee, WI, USA
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27
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Mena A, Luna JR, MacGregor F, Landa EN, Metta-Magaña A, Lee WY, Fortier S. Photoinduced Cleavage of a Strained N-C Bond in an Iron Complex Supported by Super-Bulky Amidinate and Guanidinate Ligands. Inorg Chem 2024; 63:5351-5364. [PMID: 38481142 DOI: 10.1021/acs.inorgchem.3c03953] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/26/2024]
Abstract
The reaction of Fe2(mes)4 with the super-bulky amidines and guanidines HLAr*-R (LAr*-R = [(Ar*N)2C(R)]-, Ar* = 2,6-bis(diphenylmethyl)-4-tert-butylphenyl), R = Me (LAr*-Me), tBu (LAr*-tBu), Ph (LAr*-Ph), NiPr2 (LAr*-iPr2N), and Pip (LAr*-Pip)) gives access to the three-coordinate iron-mesityl complexes (LAr*-R)Fe(mes) only where LAr*-R = LAr*-Me, LAr*-Ph, or LAr*-Pip. Subsequent protonolysis with the N-atom transfer reagent Hdbabh (Hdbabh = 2,3:5,6-dibenzo-7-azabicyclo[2.2.1]hepta-2,5-diene) is limited in success, providing in one instance a few crystals of four-coordinate (LAr*-Me)Fe(dbabh)(Hdbabh), while three-coordinate (LAr*-Pip)Fe(dbabh) is synthesized reproducibly. Complexes (LAr*-Me)Fe(dbabh)(Hdbabh) and (LAr*-Pip)Fe(dbabh) are thermally insensitive in solution to temperatures of up to 100 °C. On the other hand, both (LAr*-Me)Fe(dbabh)(Hdbabh) and (LAr*-Pip)Fe(dbabh) show sensitivity to blue LED light (395 nm), undergoing photochemical transformations. For instance, the photolysis of (LAr*-Me)Fe(dbabh)(Hdbabh) leads to N-C bond scission and C-C bond coupling across the -dbabh moieties to give four-coordinate (LAr*-Me)Fe(N=dbabh-dbabhNH2). Photolyzing pyridine-d5 (py-d5) solutions of (LAr*-Pip)Fe(dbabh) at -5 °C produces a new paramagnetic photoproduct, [P]. Due to the thermal sensitivity of compound [P], it has eluded structural characterization; yet, Evans' method measurements suggest that the iron(II) oxidation state is maintained, thereby pointing to the -dbabh moiety as the locus of chemical change. In line with this assessment, addition of excess Me3SiCl to solutions of [P] produces the iron(II) complex (LAr*-Pip)FeCl(py-d5) as shown by 1H NMR spectroscopy. Gas chromatography/mass spectrometry analysis of the solutions of [P] shows a peak in the chromatogram with a molecular mass corresponding to a formulation of C14H11N that cannot be attributed to Hdbabh. This provides evidence for the photochemical-induced isomerization of the -dbabh ligand, revealing a heretofore unknown photochemical sensitivity of this N atom transfer reagent.
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Affiliation(s)
- Asiel Mena
- Department of Chemistry and Biochemistry, University of Texas at El Paso, El Paso, Texas 79968, United States
| | - Juan R Luna
- Department of Chemistry and Biochemistry, University of Texas at El Paso, El Paso, Texas 79968, United States
| | - Frank MacGregor
- Department of Chemistry and Biochemistry, University of Texas at El Paso, El Paso, Texas 79968, United States
| | - Elizabeth Noriega Landa
- Department of Chemistry and Biochemistry, University of Texas at El Paso, El Paso, Texas 79968, United States
| | - Alejandro Metta-Magaña
- Department of Chemistry and Biochemistry, University of Texas at El Paso, El Paso, Texas 79968, United States
| | - Wen-Yee Lee
- Department of Chemistry and Biochemistry, University of Texas at El Paso, El Paso, Texas 79968, United States
| | - Skye Fortier
- Department of Chemistry and Biochemistry, University of Texas at El Paso, El Paso, Texas 79968, United States
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28
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Chen J, Yang T, Feng S, Wang L, Xie J, Liu Y. C-H Bond Activation by a Seven-Coordinate Bipyridine-Bipyrazole Ruthenium(IV) Oxo Complex. Inorg Chem 2024; 63:4790-4796. [PMID: 38422551 DOI: 10.1021/acs.inorgchem.4c00223] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/02/2024]
Abstract
Ruthenium-oxo species with high coordination numbers have long been proposed as active intermediates in catalytic oxidation chemistry. By employing a tetradentate bipyridine-bipyrazole ligand, we herein reported the synthesis of a seven-coordinate (CN7) ruthenium(IV) oxo complex, [RuIV(tpz)(pic)2(O)]2+ (RuIVO) (tpz = 6,6'-di(1H-pyrazol-1-yl)-2,2'-bipyridine, pic = 4-picoline), which exhibits high activity toward the oxidation of alkylaromatic hydrocarbons. The large kinetic isotope effects (KIE) for the oxidation of DHA/DHA-d4 (KIE = 10.3 ± 0.1) and xanthene/xanthene-d2 (KIE = 17.2 ± 0.1), as well as the linear relationship between log (rate constants) and bond dissociation energies of alkylaromatics, confirmed a mechanism of hydrogen atom abstraction.
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Affiliation(s)
- Jing Chen
- Anhui Province Key Laboratory of Advanced Catalytic Materials and Reaction Engineering, School of Chemistry and Chemical Engineering, Hefei University of Technology, Hefei 230009, P. R. China
- Institute of Intelligent Machines, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, P. R. China
| | - Tingting Yang
- Anhui Province Key Laboratory of Advanced Catalytic Materials and Reaction Engineering, School of Chemistry and Chemical Engineering, Hefei University of Technology, Hefei 230009, P. R. China
| | - Sushan Feng
- Institute of Intelligent Machines, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, P. R. China
| | - Leiyu Wang
- Anhui Province Key Laboratory of Advanced Catalytic Materials and Reaction Engineering, School of Chemistry and Chemical Engineering, Hefei University of Technology, Hefei 230009, P. R. China
| | - Jianhui Xie
- Anhui Province Key Laboratory of Advanced Catalytic Materials and Reaction Engineering, School of Chemistry and Chemical Engineering, Hefei University of Technology, Hefei 230009, P. R. China
| | - Yingying Liu
- Institute of Intelligent Machines, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, P. R. China
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29
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Lionetti D, Suseno S, Shiau AA, de Ruiter G, Agapie T. Redox Processes Involving Oxygen: The Surprising Influence of Redox-Inactive Lewis Acids. JACS AU 2024; 4:344-368. [PMID: 38425928 PMCID: PMC10900226 DOI: 10.1021/jacsau.3c00675] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Revised: 12/12/2023] [Accepted: 12/13/2023] [Indexed: 03/02/2024]
Abstract
Metalloenzymes with heteromultimetallic active sites perform chemical reactions that control several biogeochemical cycles. Transformations catalyzed by such enzymes include dioxygen generation and reduction, dinitrogen reduction, and carbon dioxide reduction-instrumental transformations for progress in the context of artificial photosynthesis and sustainable fertilizer production. While the roles of the respective metals are of interest in all these enzymatic transformations, they share a common factor in the transfer of one or multiple redox equivalents. In light of this feature, it is surprising to find that incorporation of redox-inactive metals into the active site of such an enzyme is critical to its function. To illustrate, the presence of a redox-inactive Ca2+ center is crucial in the Oxygen Evolving Complex, and yet particularly intriguing given that the transformation catalyzed by this cluster is a redox process involving four electrons. Therefore, the effects of redox inactive metals on redox processes-electron transfer, oxygen- and hydrogen-atom transfer, and O-O bond cleavage and formation reactions-mediated by transition metals have been studied extensively. Significant effects of redox inactive metals have been observed on these redox transformations; linear free energy correlations between Lewis acidity and the redox properties of synthetic model complexes are observed for several reactions. In this Perspective, these effects and their relevance to multielectron processes will be discussed.
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Affiliation(s)
| | - Sandy Suseno
- Division of Chemistry and
Chemical Engineering, California Institute
of Technology, 1200 East California Boulevard, MC 127-72, Pasadena, California 91125, United States
| | - Angela A. Shiau
- Division of Chemistry and
Chemical Engineering, California Institute
of Technology, 1200 East California Boulevard, MC 127-72, Pasadena, California 91125, United States
| | - Graham de Ruiter
- Division of Chemistry and
Chemical Engineering, California Institute
of Technology, 1200 East California Boulevard, MC 127-72, Pasadena, California 91125, United States
| | - Theodor Agapie
- Division of Chemistry and
Chemical Engineering, California Institute
of Technology, 1200 East California Boulevard, MC 127-72, Pasadena, California 91125, United States
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30
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Rasheed W, Pal N, Aboelenen AM, Banerjee S, Oloo WN, Klein JEMN, Fan R, Xiong J, Guo Y, Que L. NMR and Mössbauer Studies Reveal a Temperature-Dependent Switch from S = 1 to 2 in a Nonheme Oxoiron(IV) Complex with Faster C-H Bond Cleavage Rates. J Am Chem Soc 2024; 146:3796-3804. [PMID: 38299607 PMCID: PMC11238627 DOI: 10.1021/jacs.3c10694] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2024]
Abstract
S = 2 FeIV═O centers generated in the active sites of nonheme iron oxygenases cleave substrate C-H bonds at rates significantly faster than most known synthetic FeIV═O complexes. Unlike the majority of the latter, which are S = 1 complexes, [FeIV(O)(tris(2-quinolylmethyl)amine)(MeCN)]2+ (3) is a rare example of a synthetic S = 2 FeIV═O complex that cleaves C-H bonds 1000-fold faster than the related [FeIV(O)(tris(pyridyl-2-methyl)amine)(MeCN)]2+ complex (0). To rationalize this significant difference, a systematic comparison of properties has been carried out on 0 and 3 as well as related complexes 1 and 2 with mixed pyridine (Py)/quinoline (Q) ligation. Interestingly, 2 with a 2-Q-1-Py donor combination cleaves C-H bonds at 233 K with rates approaching those of 3, even though Mössbauer analysis reveals 2 to be S = 1 at 4 K. At 233 K however, 2 becomes S = 2, as shown by its 1H NMR spectrum. These results demonstrate a unique temperature-dependent spin-state transition from triplet to quintet in oxoiron(IV) chemistry that gives rise to the high C-H bond cleaving reactivity observed for 2.
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Affiliation(s)
- Waqas Rasheed
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Nabhendu Pal
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Ahmed M Aboelenen
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Saikat Banerjee
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Williamson N Oloo
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Johannes E M N Klein
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Ruixi Fan
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - Jin Xiong
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - Yisong Guo
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - Lawrence Que
- Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States
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31
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Tepaske MA, Fitterer A, Verplancke H, Delony D, Neben MC, de Bruin B, Holthausen MC, Schneider S. C-H Bond Activation by Iridium(III) and Iridium(IV) Oxo Complexes. Angew Chem Int Ed Engl 2024; 63:e202316729. [PMID: 38116899 DOI: 10.1002/anie.202316729] [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: 11/03/2023] [Revised: 12/18/2023] [Accepted: 12/19/2023] [Indexed: 12/21/2023]
Abstract
Oxidation of an iridium(III) oxo precursor enabled the structural, spectroscopic, and quantum-chemical characterization of the first well-defined iridium(IV) oxo complex. Side-by-side examination of the proton-coupled electron transfer thermochemistry revealed similar driving forces for the isostructural oxo complexes in two redox states due to compensating contributions from H+ and e- transfer. However, C-H activation of dihydroanthracene revealed significant hydrogen tunneling for the distinctly more basic iridium(III) oxo complex. Our findings complement the growing body of data that relate tunneling to ground state properties as predictors for the selectivity of C-H bond activation.
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Affiliation(s)
- Martijn A Tepaske
- Georg-August-Universität, Institut für Anorganische Chemie, Tammanstraβe 4, 37077, Göttingen, Germany
| | - Arnd Fitterer
- Institut für Anorganische und Analytische Chemie, Goethe-Universität, Max-von-Laue-Straβe 7, 60438, Frankfurt am Main, Germany
| | - Hendrik Verplancke
- Institut für Anorganische und Analytische Chemie, Goethe-Universität, Max-von-Laue-Straβe 7, 60438, Frankfurt am Main, Germany
| | - Daniel Delony
- Georg-August-Universität, Institut für Anorganische Chemie, Tammanstraβe 4, 37077, Göttingen, Germany
| | - Marc C Neben
- Georg-August-Universität, Institut für Anorganische Chemie, Tammanstraβe 4, 37077, Göttingen, Germany
| | - Bas de Bruin
- Homogeneous, Supramolecular and Bio-Inspired Catalysis Group, van't Hoff Institute for Molecular Sciences (HIMS), Science Park 904, 1098XH, Amsterdam, The Netherlands
| | - Max C Holthausen
- Institut für Anorganische und Analytische Chemie, Goethe-Universität, Max-von-Laue-Straβe 7, 60438, Frankfurt am Main, Germany
| | - Sven Schneider
- Georg-August-Universität, Institut für Anorganische Chemie, Tammanstraβe 4, 37077, Göttingen, Germany
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32
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Katoch A, Mandal D. High-valent nonheme Fe(IV)O/Ru(IV)O complexes catalyze C-H activation reactivity and hydrogen tunneling: a comparative DFT investigation. Dalton Trans 2024; 53:2386-2394. [PMID: 38214597 DOI: 10.1039/d3dt03155a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2024]
Abstract
A comprehensive density functional theory investigation has been presented towards the comparison of the C-H activation reactivity between high-valent iron-oxo and ruthenium-oxo complexes. A total of four compounds, e.g., [Ru(IV)O(tpy-dcbpy)] (1), [Fe(IV)O(tpy-dcbpy)] (1'), [Ru(IV)O(TMCS)] (2), and [Fe(IV)O(TMCS)] (2'), have been considered for this investigation. The macrocyclic ligand framework tpy(dcbpy) implies tpy = 2,2':6',2''-terpyridine, dcbpy = 5,5'-dicarboxy-2,2'-bipyridine, and TMCS is TMC with an axially tethered -SCH2CH2 group. Compounds 1 and 2' are experimentally synthesized standard complexes with Ru and Fe, whereas compounds 1' and 2 were considered to keep the macrocycle intact when switching the central metal atom. Three reactants including benzyl alcohol, ethyl benzene, and dihydroanthracene were selected as substrates for C-H activation. It is noteworthy to mention that Fe(IV)O complexes exhibit higher reactivity than those of their Ru(IV)O counterparts. Furthermore, regardless of the central metal, the complex featuring a tpy-dcbpy macrocycle demonstrates higher reactivity than that of TMCS. Here, a thorough analysis of the reactivity-controlling characteristics-such as spin state, steric factor, distortion energy, energy of the electron acceptor orbital, and quantum mechanical tunneling-was conducted. Fe(IV)O exhibits the exchanged enhanced two-state-reactivity with the quintet reactive state, whereas Ru(IV)O has only a triplet reactive state. Both the distortion energy and acceptor orbital energy are low in the case of Fe(IV)O supporting its higher reactivity. All the investigated C-H activation processes involve a significant contribution from hydrogen tunneling, which is more pronounced in the case of Ru, although it cannot alter the reactivity pattern. Furthermore, it has also been found that, independent of the central metal, aliphatic hydroxylation is always preferable to aromatic hydroxylation. Overall, this work is successful in establishing and investigating the cause of enzymes' natural preference for Fe over Ru as a cofactor for C-H activation enzymes.
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Affiliation(s)
- Akanksha Katoch
- Department of Chemistry and Biochemistry, Thapar Institute of Engineering and Technology, Patiala-147001, Punjab, India.
| | - Debasish Mandal
- Department of Chemistry and Biochemistry, Thapar Institute of Engineering and Technology, Patiala-147001, Punjab, India.
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33
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Wang R, Pan Y, Feng S, Liang C, Xie J, Lau TC, Liu Y. Structure and reactivity of a seven-coordinate ruthenium acylperoxo complex. Chem Commun (Camb) 2024; 60:312-315. [PMID: 38063010 DOI: 10.1039/d3cc04751b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2024]
Abstract
The use of metal-acylperoxo complexes as oxidants has been little explored. Herein we report the synthesis and characterization of the first seven-coordinate Ru-acylperoxo complex, [RuIV(bdpm)(pic)2(mCPBA)]+ (H2bdpm = [2,2'-bipyridine]-6,6'-diylbis(diphenylmethanol); pic = 4-picoline; HmCPBA = m-chloroperbenzoic acid). This complex is a highly reactive oxidant for C-H bond activation and O-atom transfer reactions.
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Affiliation(s)
- Rui Wang
- Institute of Intelligent Machines, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, P. R. China.
- Science Island Branch, Graduate School of USTC, Hefei 230026, P. R. China
| | - Yunling Pan
- Institute of Intelligent Machines, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, P. R. China.
- Anhui Province Key Laboratory of Advanced Catalytic Materials and Reaction Engineering, School of Chemistry and Chemical Engineering, Hefei University of Technology, Hefei 230009, P. R. China
| | - Sushan Feng
- Institute of Intelligent Machines, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, P. R. China.
- Institutes of Physical Science and Information Technology, Anhui University, Hefei 230601, P. R. China
| | - Chenyi Liang
- Institute of Intelligent Machines, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, P. R. China.
- Science Island Branch, Graduate School of USTC, Hefei 230026, P. R. China
| | - Jianhui Xie
- Anhui Province Key Laboratory of Advanced Catalytic Materials and Reaction Engineering, School of Chemistry and Chemical Engineering, Hefei University of Technology, Hefei 230009, P. R. China
| | - Tai-Chu Lau
- Department of Chemistry, City University of Hong Kong, Kowloon Tong, Hong Kong, P. R. China
| | - Yingying Liu
- Institute of Intelligent Machines, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, P. R. China.
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34
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Lakk-Bogáth D, Pintarics D, Török P, Kaizer J. Influence of Equatorial Co-Ligands on the Reactivity of LFe IIIOIPh. Molecules 2023; 29:58. [PMID: 38202641 PMCID: PMC10779584 DOI: 10.3390/molecules29010058] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2023] [Revised: 12/18/2023] [Accepted: 12/19/2023] [Indexed: 01/12/2024] Open
Abstract
Previous biomimetic studies clearly proved that equatorial ligands significantly influence the redox potential and thus the stability/reactivity of biologically important oxoiron intermediates; however, no such studies were performed on FeIIIOIPh species. In this study, the influence of substituted pyridine co-ligands on the reactivity of iron(III)-iodosylbenzene adduct has been investigated in sulfoxidation and epoxidation reactions. Selective oxidation of thioanisole, cis-cyclooctene, and cis- and trans-stilbene in the presence of a catalytic amount of [FeII(PBI)3](OTf)2 with PhI(OAc)2 provide products in good to excellent yields through an FeIIIOIPh intermediate depending on the co-ligand (4R-Py) used. Several mechanistic studies were performed to gain more insight into the mechanism of oxygen atom transfer (OAT) reactions to support the reactive intermediate and investigate the effect of the equatorial co-ligands. Based on competitive experiments, including a linear free-energy relationship between the relative reaction rates (logkrel) and the σp (4R-Py) parameters, strong evidence has been observed for the electrophilic character of the reactive species. The presence of the [(PBI)2(4R-Py)FeIIIOIPh]3+ intermediates and the effect of the co-ligands was also supported by UV-visible measurements, including the color change from red to green and the hypsochromic shifts in the presence of co-ligands. This is another indication that the title iron(III)-iodosylbenzene adduct is able to oxygenate sulfides and alkenes before it is transformed into the oxoiron form by cleavage of the O-I bond.
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Affiliation(s)
| | | | | | - József Kaizer
- Research Group of Bioorganic and Biocoordination Chemistry, University of Pannonia, H-8201 Veszprém, Hungary; (D.L.-B.); (D.P.); (P.T.)
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35
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Sarkar A, Das S, Mondal P, Maiti B, Sen Gupta S. Synthesis, Characterization, and Reactivity of High-Valent Carbene Dicarboxamide-Based Nickel Pincer Complexes. Inorg Chem 2023. [PMID: 38001041 DOI: 10.1021/acs.inorgchem.3c03465] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2023]
Abstract
High-valent metal-fluoride complexes are currently being explored for concerted proton-electron transfer (CPET) reactions, the driving force being the high bond dissociation energy of H-F (BDEH-F = 135 kcal/mol) that is formed after the reaction. Ni(III)-fluoride-based complexes on the pyridine dicarboxamide pincer ligand framework have been utilized for CPET reactions toward phenols and hydrocarbons. We have replaced the central pyridine ligand with an N-heterocyclic carbene carbene to probe its effect in both stabilizing the high-valent Ni(III) state and its ability to initiate CPET reactions. We report a monomeric carbene-diamide-based Ni(II)-fluoride pincer complex that was characterized through 1H/19F NMR, mass spectrometry, UV-vis, and X-ray crystallography analysis. Although carbenes and deprotonated carboxamides in the Ni(II)-fluoride complex are expected to stabilize the Ni(III) state upon oxidation, the Ni(III)/Ni(II) redox process occurred at very high potential (0.87 V vs Fc+/Fc, dichloromethane) and was irreversible. Structural studies indicate significant distortion in the imidazolium "NCN" carbene plane of Ni(II)-fluoride caused by the formation of six-membered metallacycles. The high-valent NiIII-fluoride analogue was synthesized by the addition of 1.0 equiv CTAN (ceric tetrabutylammonium nitrate) in dichloromethane at -20 °C which was characterized by UV-vis, mass spectrometry, and EPR spectroscopy. Density functional theory studies indicate that the Ni-carbene bond elongated, while the Ni-F bond shortened upon oxidation to the Ni(III) species. The high-valent Ni(III)-fluoride was found to react with the substituted phenols. Analysis of the KIE and linear free energy relationship correlates well with the CPET nature of the reaction. Preliminary analysis indicates that the CPET is asynchronous and is primarily driven by the E0' of the Ni(III)-fluoride complex.
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Affiliation(s)
- Aniruddha Sarkar
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur 741246, India
| | - Soumadip Das
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur 741246, India
| | - Prasenjit Mondal
- Department of Chemistry, Indian Institute of Technology Tirupati (IIT Tirupati), Tirupati, AP 517619, India
| | - Biswajit Maiti
- Department of Chemistry, Institute of Science, Banaras Hindu University, Varanasi 221005, India
| | - Sayam Sen Gupta
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Kolkata, Mohanpur 741246, India
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36
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Chatterjee S, Paine TK. Dioxygen Reduction and Bioinspired Oxidations by Non-heme Iron(II)-α-Hydroxy Acid Complexes. Acc Chem Res 2023; 56:3175-3187. [PMID: 37938969 DOI: 10.1021/acs.accounts.3c00449] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2023]
Abstract
Aerobic organisms involve dioxygen-activating iron enzymes to perform various metabolically relevant chemical transformations. Among these enzymes, mononuclear non-heme iron enzymes reductively activate dioxygen to catalyze diverse biological oxidations, including oxygenation of C-H and C═C bonds and C-C bond cleavage with amazing selectivity. Several non-heme enzymes utilize organic cofactors as electron sources for dioxygen reduction, leading to the generation of iron-oxygen intermediates that act as active oxidants in the catalytic cycle. These unique enzymatic reactions influence the design of small molecule synthetic compounds to emulate enzyme functions and to develop bioinspired catalysts for performing selective oxidation of organic substrates with dioxygen. Selective electron transfer during dioxygen reduction on iron centers of synthetic models by a sacrificial reductant requires appropriate design strategies. Taking lessons from the role of enzyme-cofactor complexes in the selective electron transfer process, our group utilized ternary iron(II)-α-hydroxy acid complexes supported by polydentate ligands for dioxygen reduction and bioinspired oxidations. This Account focuses on the role of coordinated sacrificial reductants in the selective electron transfer for dioxygen reduction by iron complexes and highlights the versatility of iron(II)-α-hydroxy acid complexes in affecting dioxygen-dependent oxidation/oxygenation reactions. The iron(II)-coordinated α-hydroxy acid anions undergo two-electron oxidative decarboxylation concomitant with the generation of reactive iron-oxygen oxidants. A nucleophilic iron(II)-hydroperoxo species was intercepted in the decarboxylation pathway. In the presence of a Lewis acid, the O-O bond of the nucleophilic oxidant is heterolytically cleaved to generate an electrophilic iron(IV)-oxo-hydroxo oxidant. Most importantly, the oxidants generated with or without Lewis acid can carry out cis-dihydroxylation of alkenes. Furthermore, the electrophilic iron-oxygen oxidant selectively hydroxylates strong C-H bonds. Another electrophilic iron(IV)-oxo oxidant, generated from the iron(II)-α-hydroxy acid complexes in the presence of a protic acid, carries out C-H bond halogenation by using a halide anion.Thus, different metal-oxygen intermediates could be generated from dioxygen using a single reductant, and the reactivity of the ternary complexes can be tuned using external additives (Lewis/protic acid). The catalytic potential of the iron(II)-α-hydroxy complexes in performing O2-dependent oxygenations has been demonstrated. Different factors that govern the reactivity of iron-oxygen oxidants from ternary iron(II) complexes are presented. The versatile reactivity of the oxidants provides useful insights into developing catalytic methods for the selective incorporation of oxidized functionalities under environmentally benign conditions using aerial oxygen as the terminal oxidant.
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Affiliation(s)
- Sayanti Chatterjee
- 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
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37
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Li Y, Singh R, Sinha A, Lisensky GC, Haukka M, Nilsson J, Yiga S, Demeshko S, Gross SJ, Dechert S, Gonzalez A, Farias G, Wendt OF, Meyer F, Nordlander E. Nonheme Fe IV═O Complexes Supported by Four Pentadentate Ligands: Reactivity toward H- and O- Atom Transfer Processes. Inorg Chem 2023; 62:18338-18356. [PMID: 37913548 PMCID: PMC10647104 DOI: 10.1021/acs.inorgchem.3c02526] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2023] [Revised: 10/06/2023] [Accepted: 10/11/2023] [Indexed: 11/03/2023]
Abstract
Four new pentadentate N5-donor ligands, [N-(1-methyl-2-imidazolyl)methyl-N-(2-pyridyl)-methyl-N-(bis-2-pyridylmethyl)-amine] (L1), [N-bis(1-methyl-2-imidazolyl)methyl-N-(bis-2-pyridylmethyl)amine] (L2), (N-(isoquinolin-3-ylmethyl)-1,1-di(pyridin-2-yl)-N-(pyridin-2-ylmethyl)methanamine (L3), and N,N-bis(isoquinolin-3-ylmethyl)-1,1-di(pyridin-2-yl)methanamine (L4), have been synthesized based on the N4Py ligand framework, where one or two pyridyl arms of the N4Py parent are replaced by (N-methyl)imidazolyl or N-(isoquinolin-3-ylmethyl) moieties. Using these four pentadentate ligands, the mononuclear complexes [FeII(CH3CN)(L1)]2+ (1a), [FeII(CH3CN)(L2)]2+ (2a), [FeII(CH3CN)(L3)]2+ (3a), and [FeII(CH3CN)(L4)]2+ (4a) have been synthesized and characterized. The half-wave potentials (E1/2) of the complexes become more positive in the order: 2a < 1a < 4a ≤ 3a ≤ [Fe(N4Py)(CH3CN)]2+. The order of redox potentials correlates well with the Fe-Namine distances observed by crystallography, which are 2a > 1a ≥ 4a > 3a ≥ [Fe(N4Py)(CH3CN)]2+. The corresponding ferryl complexes [FeIV(O)(L1)]2+ (1b), [FeIV(O)(L2)]2+ (2b), [FeIV(O)(L3)]2+ (3b), and [FeIV(O)(L4)]2+ (4b) were prepared by the reaction of the ferrous complexes with isopropyl 2-iodoxybenzoate (IBX ester) in acetonitrile. The greenish complexes 3b and 4b were also isolated in the solid state by the reaction of the ferrous complexes in CH3CN with ceric ammonium nitrate in water. Mössbauer spectroscopy and magnetic measurements (using superconducting quantum interference device) show that the four complexes 1b, 2b, 3b, and 4b are low-spin (S = 1) FeIV═O complexes. UV/vis spectra of the four FeIV═O complexes in acetonitrile show typical long-wavelength absorptions of around 700 nm, which are expected for FeIV═O complexes with N4Py-type ligands. The wavelengths of these absorptions decrease in the following order: 721 nm (2b) > 706 nm (1b) > 696 nm (4b) > 695 nm (3b) = 695 nm ([FeIV(O) (N4Py)]2+), indicating that the replacement of the pyridyl arms with (N-methyl) imidazolyl moieties makes L1 and L2 exert weaker ligand fields than the parent N4Py ligand, while the ligand field strengths of L3 and L4 are similar to the N4Py parent despite the replacement of the pyridyl arms with N-(isoquinolin-3-ylmethyl) moieties. Consequently, complexes 1b and 2b tend to be less stable than the parent [FeIV(O)(N4Py)]2+ complex: the half-life sequence at room temperature is 1.67 h (2b) < 16 h (1b) < 45 h (4b) < 63 h (3b) ≈ 60 h ([FeIV(O)(N4Py)]2+). Compared to the parent complex, 1b and 2b exhibit enhanced reactivity in both the oxidation of thioanisole in the oxygen atom transfer (OAT) reaction and the oxygenation of C-H bonds of aromatic and aliphatic substrates, presumed to occur via an oxygen rebound process. Furthermore, the second-order rate constants for hydrogen atom transfer (HAT) reactions affected by the ferryl complexes can be directly related to the C-H bond dissociation energies of a range of substrates that have been studied. Using either IBX ester or H2O2 as an oxidant, all four new FeII complexes display good performance in catalytic reactions involving both HAT and OAT reactions.
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Affiliation(s)
- Yong Li
- Chemical
Physics, Department of Chemistry, Lund University, Box 124, Lund SE-221 00, Sweden
| | - Reena Singh
- Chemical
Physics, Department of Chemistry, Lund University, Box 124, Lund SE-221 00, Sweden
| | - Arup Sinha
- Chemical
Physics, Department of Chemistry, Lund University, Box 124, Lund SE-221 00, Sweden
| | - George C. Lisensky
- Department
of Chemistry, Beloit College, 700 College Street, Beloit, Wisconsin 53511, United States
| | - Matti Haukka
- Department
of Chemistry, University of Jyväskylä, P.O. Box-35, Jyväskylä FI-40014, Finland
| | - Justin Nilsson
- Chemical
Physics, Department of Chemistry, Lund University, Box 124, Lund SE-221 00, Sweden
| | - Solomon Yiga
- Centre
for Analysis and Synthesis, Department of Chemistry, Lund University, P.O. Box 124, Lund SE-22100, Sweden
| | - Serhiy Demeshko
- Georg-August
Universität Göttingen, Institut
für Anorganische Chemie, Tammanstrasse 4, Göttingen D-37077, Germany
| | - Sophie Jana Gross
- Georg-August
Universität Göttingen, Institut
für Anorganische Chemie, Tammanstrasse 4, Göttingen D-37077, Germany
| | - Sebastian Dechert
- Georg-August
Universität Göttingen, Institut
für Anorganische Chemie, Tammanstrasse 4, Göttingen D-37077, Germany
| | - Ana Gonzalez
- MAX IV Laboratory, Lund University, P.O.
Box 118, Lund SE-221 00, Sweden
| | - Giliandro Farias
- Department
of Chemistry, Federal University of Santa
Catarina, Florianópolis 88040900, Santa Catarina, Brazil
| | - Ola F. Wendt
- Centre
for Analysis and Synthesis, Department of Chemistry, Lund University, P.O. Box 124, Lund SE-22100, Sweden
| | - Franc Meyer
- Georg-August
Universität Göttingen, Institut
für Anorganische Chemie, Tammanstrasse 4, Göttingen D-37077, Germany
| | - Ebbe Nordlander
- Chemical
Physics, Department of Chemistry, Lund University, Box 124, Lund SE-221 00, Sweden
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38
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Hou K, Börgel J, Jiang HZH, SantaLucia DJ, Kwon H, Zhuang H, Chakarawet K, Rohde RC, Taylor JW, Dun C, Paley MV, Turkiewicz AB, Park JG, Mao H, Zhu Z, Alp EE, Zhao J, Hu MY, Lavina B, Peredkov S, Lv X, Oktawiec J, Meihaus KR, Pantazis DA, Vandone M, Colombo V, Bill E, Urban JJ, Britt RD, Grandjean F, Long GJ, DeBeer S, Neese F, Reimer JA, Long JR. Reactive high-spin iron(IV)-oxo sites through dioxygen activation in a metal-organic framework. Science 2023; 382:547-553. [PMID: 37917685 DOI: 10.1126/science.add7417] [Citation(s) in RCA: 18] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2022] [Accepted: 09/24/2023] [Indexed: 11/04/2023]
Abstract
In nature, nonheme iron enzymes use dioxygen to generate high-spin iron(IV)=O species for a variety of oxygenation reactions. Although synthetic chemists have long sought to mimic this reactivity, the enzyme-like activation of O2 to form high-spin iron(IV) = O species remains an unrealized goal. Here, we report a metal-organic framework featuring iron(II) sites with a local structure similar to that in α-ketoglutarate-dependent dioxygenases. The framework reacts with O2 at low temperatures to form high-spin iron(IV) = O species that are characterized using in situ diffuse reflectance infrared Fourier transform, in situ and variable-field Mössbauer, Fe Kβ x-ray emission, and nuclear resonance vibrational spectroscopies. In the presence of O2, the framework is competent for catalytic oxygenation of cyclohexane and the stoichiometric conversion of ethane to ethanol.
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Affiliation(s)
- Kaipeng Hou
- Department of Chemistry, University of California, Berkeley, CA 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Jonas Börgel
- Department of Chemistry, University of California, Berkeley, CA 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Henry Z H Jiang
- Department of Chemistry, University of California, Berkeley, CA 94720, USA
| | - Daniel J SantaLucia
- Max Planck Institute for Chemical Energy Conversion, D-45470 Mülheim an der Ruhr, Germany
- Max-Planck-Institut für Kohlenforschung, D-45470 Mülheim an der Ruhr, Germany
| | - Hyunchul Kwon
- Department of Chemistry, University of California, Berkeley, CA 94720, USA
| | - Hao Zhuang
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, CA 94720, USA
- Department of Materials Science and Engineering, University of California, Berkeley, CA 94720, USA
| | | | - Rachel C Rohde
- Department of Chemistry, University of California, Berkeley, CA 94720, USA
| | - Jordan W Taylor
- Department of Chemistry, University of California, Berkeley, CA 94720, USA
| | - Chaochao Dun
- The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Maria V Paley
- Department of Chemistry, University of California, Berkeley, CA 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Ari B Turkiewicz
- Department of Chemistry, University of California, Berkeley, CA 94720, USA
| | - Jesse G Park
- Department of Chemistry, University of California, Berkeley, CA 94720, USA
| | - Haiyan Mao
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, CA 94720, USA
| | - Ziting Zhu
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
- Department of Materials Science and Engineering, University of California, Berkeley, CA 94720, USA
| | - E Ercan Alp
- Advanced Photon Source, Argonne National Laboratory, Lemont, IL 60439, USA
| | - Jiyong Zhao
- Advanced Photon Source, Argonne National Laboratory, Lemont, IL 60439, USA
| | - Michael Y Hu
- Advanced Photon Source, Argonne National Laboratory, Lemont, IL 60439, USA
| | - Barbara Lavina
- Advanced Photon Source, Argonne National Laboratory, Lemont, IL 60439, USA
- Center for Advanced Radiation Sources, The University of Chicago, Chicago, IL 60637, USA
| | - Sergey Peredkov
- Max Planck Institute for Chemical Energy Conversion, D-45470 Mülheim an der Ruhr, Germany
| | - Xudong Lv
- Department of Chemistry, University of California, Berkeley, CA 94720, USA
| | - Julia Oktawiec
- Department of Chemistry, Northwestern University, Evanston, IL 60208, USA
| | - Katie R Meihaus
- Department of Chemistry, University of California, Berkeley, CA 94720, USA
| | | | - Marco Vandone
- Department of Chemistry, University of Milan, 20133 Milan, Italy
| | - Valentina Colombo
- Department of Chemistry, University of Milan, 20133 Milan, Italy
- Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali (INSTM), UdR Milano, Via Golgi 19, 20133 Milano, Italy
| | - Eckhard Bill
- Max Planck Institute for Chemical Energy Conversion, D-45470 Mülheim an der Ruhr, Germany
| | - Jeffrey J Urban
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
- The Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - R David Britt
- Department of Chemistry, University of California, Davis, CA 95616, USA
- Miller Institute for Basic Research in Science, University of California, Berkeley CA 94720, USA
| | - Fernande Grandjean
- Department of Chemistry, Missouri University of Science and Technology, University of Missouri, Rolla, MO 65409, USA
| | - Gary J Long
- Department of Chemistry, Missouri University of Science and Technology, University of Missouri, Rolla, MO 65409, USA
| | - Serena DeBeer
- Max Planck Institute for Chemical Energy Conversion, D-45470 Mülheim an der Ruhr, Germany
| | - Frank Neese
- Max-Planck-Institut für Kohlenforschung, D-45470 Mülheim an der Ruhr, Germany
| | - Jeffrey A Reimer
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, CA 94720, USA
| | - Jeffrey R Long
- Department of Chemistry, University of California, Berkeley, CA 94720, USA
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
- Department of Chemical and Biomolecular Engineering, University of California, Berkeley, CA 94720, USA
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39
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Paris JC, Hu S, Wen A, Weitz AC, Cheng R, Gee LB, Tang Y, Kim H, Vegas A, Chang WC, Elliott SJ, Liu P, Guo Y. An S=1 Iron(IV) Intermediate Revealed in a Non-Heme Iron Enzyme-Catalyzed Oxidative C-S Bond Formation. Angew Chem Int Ed Engl 2023; 62:e202309362. [PMID: 37640689 PMCID: PMC10592081 DOI: 10.1002/anie.202309362] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2023] [Revised: 08/11/2023] [Accepted: 08/28/2023] [Indexed: 08/31/2023]
Abstract
Ergothioneine (ESH) and ovothiol A (OSHA) are two natural thiol-histidine derivatives. ESH has been implicated as a longevity vitamin and OSHA inhibits the proliferation of hepatocarcinoma. The key biosynthetic step of ESH and OSHA in the aerobic pathways is the O2 -dependent C-S bond formation catalyzed by non-heme iron enzymes (e.g., OvoA in ovothiol biosynthesis), but due to the lack of identification of key reactive intermediate the mechanism of this novel reaction is unresolved. In this study, we report the identification and characterization of a kinetically competent S=1 iron(IV) intermediate supported by a four-histidine ligand environment (three from the protein residues and one from the substrate) in enabling C-S bond formation in OvoA from Methyloversatilis thermotoleran, which represents the first experimentally observed intermediate spin iron(IV) species in non-heme iron enzymes. Results reported in this study thus set the stage to further dissect the mechanism of enzymatic oxidative C-S bond formation in the OSHA biosynthesis pathway. They also afford new opportunities to study the structure-function relationship of high-valent iron intermediates supported by a histidine rich ligand environment.
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Affiliation(s)
- Jared C Paris
- Department of Chemistry, Carnegie Mellon University, 4400 Fifth Ave., Pittsburgh, PA 15213, USA
| | - Sha Hu
- Department of Chemistry, Boston University, 590 Commonwealth Ave., Boston, MA 02215, USA
| | - Aiwen Wen
- Department of Chemistry, Boston University, 590 Commonwealth Ave., Boston, MA 02215, USA
| | - Andrew C Weitz
- Department of Chemistry, Boston University, 590 Commonwealth Ave., Boston, MA 02215, USA
| | - Ronghai Cheng
- Department of Chemistry, Boston University, 590 Commonwealth Ave., Boston, MA 02215, USA
| | - Leland B Gee
- LCLS, SLAC National Accelerator Laboratory, 2575 Sand Hill Rd., Menlo Park, CA 94025, USA
| | - Yijie Tang
- Department of Chemistry, Carnegie Mellon University, 4400 Fifth Ave., Pittsburgh, PA 15213, USA
| | - Hyomin Kim
- Department of Chemistry, Boston University, 590 Commonwealth Ave., Boston, MA 02215, USA
| | - Arturo Vegas
- Department of Chemistry, Boston University, 590 Commonwealth Ave., Boston, MA 02215, USA
| | - Wei-Chen Chang
- Department of Chemistry, North Carolina State University, Raleigh, NC 27695, USA
| | - Sean J Elliott
- Department of Chemistry, Boston University, 590 Commonwealth Ave., Boston, MA 02215, USA
| | - Pinghua Liu
- Department of Chemistry, Boston University, 590 Commonwealth Ave., Boston, MA 02215, USA
| | - Yisong Guo
- Department of Chemistry, Carnegie Mellon University, 4400 Fifth Ave., Pittsburgh, PA 15213, USA
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40
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Sen A, Ansari A, Swain A, Pandey B, Rajaraman G. Probing the Origins of Puzzling Reactivity in Fe/Mn-Oxo/Hydroxo Species toward C-H Bonds: A DFT and Ab Initio Perspective. Inorg Chem 2023; 62:14931-14941. [PMID: 37650771 DOI: 10.1021/acs.inorgchem.3c01632] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/01/2023]
Abstract
Activation of C-H bonds using an earth-abundant metal catalyst is one of the top challenges of chemistry, where high-valent Mn/Fe-oxo(hydroxo) biomimic species play an important role. There are several open questions related to the comparative oxidative abilities of these species, and a unifying concept that could accommodate various factors influencing reactivity is lacking. To shed light on these open questions, here, we have used a combination of density functional theory (DFT) (B3LYP-D3/def2-TZVP) and ab initio (CASSCF/NEVPT2) calculations to study a series of high-valent metal-oxo species [Mn+H3buea(O/OH)] (M = Mn and Fe, n = II to V; H3buea = tris[(N'-tert-butylureaylato)-N-ethylene)]aminato towards the activation of dihydroanthracene (DHA). The H-bonding network in the ligand architecture influences the ground state-excited state gap and brings several excited states of the same spin multiplicity closer in energy, which triggers reactivity via one of those excited states, reducing the kinetic barriers for the C-H bond activation and rationalizing several puzzling reactivity trends observed in various high-valent Mn/Fe-oxo(hydroxo) species.
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Affiliation(s)
- Asmita Sen
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai400076, India
| | - Azaj Ansari
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai400076, India
| | - Abinash Swain
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai400076, India
| | - Bhawana Pandey
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai400076, India
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai400076, India
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41
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Radović A, Wolford NJ, Li H, Brennessel WW, Xu H, Neidig ML. Mechanistic Studies of Iron-PyBOX-Catalyzed Olefin Amino-Oxygenation with Functionalized Hydroxylamines. Organometallics 2023; 42:1810-1817. [PMID: 37502313 PMCID: PMC10369677 DOI: 10.1021/acs.organomet.3c00067] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Indexed: 07/29/2023]
Abstract
Iron-catalyzed amino-oxygenation of olefins often uses discrete ligands to increase reactivity and broaden substrate scope. This work is focused on examining ligand effects on reactivity and in situ iron speciation in a system which utilizes a bisoxazoline ligand. Freeze-trapped 57Fe Mössbauer and EPR spectroscopies as well as SC-XRD experiments were utilized to isolate and identify the species formed during the catalytic reaction of amino-oxygenation of olefins with functionalized hydroxylamines, as well as in the precatalytic mixture of iron salt and ligand. Experiments revealed significant influence of ligand and solvent on the speciation in the precatalytic mixture which led to the formation of different species which had significant influence on the reactivity. In situ experiments showed no evidence for the formation of an Fe(IV)-nitrene intermediate, and the isolation of a reactive intermediate was unsuccessful, suggesting that the use of the PyBOX ligand led to the formation of more reactive intermediates than observed in the previously studied system, preventing direct detection of intermediate species. However, isolation of the seven coordinate Fe(III) species with three carboxylate units of the hydroxylamine and spin-trap EPR experiments suggest formation of a species with unpaired electron density on the hydroxylamine nitrogen, which is in accordance with formation of a potential iron iminyl radical species, as recently proposed in literature. An observed increase in yield when substrates devoid of C-H bonds as well as isolation of a ring-closed dead-end species with substrates containing these bonds suggests the identity of the functionalized hydroxylamine can dictate the reactivity observed in these reactions.
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Affiliation(s)
- Aleksa Radović
- Department
of Chemistry, University of Rochester, Rochester, New York 14627, USA
| | - Nikki J. Wolford
- Department
of Chemistry, University of Rochester, Rochester, New York 14627, USA
| | - Hongze Li
- Department
of Chemistry, Brandeis University, Waltham, Massachusetts 02453, USA
| | | | - Hao Xu
- Department
of Chemistry, Brandeis University, Waltham, Massachusetts 02453, USA
| | - Michael L. Neidig
- Department
of Chemistry, University of Rochester, Rochester, New York 14627, USA
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42
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Sun C, Jaimes JL, Follmer AH, Ziller JW, Borovik AS. Selective C-H Bond Cleavage with a High-Spin Fe IV-Oxido Complex. Molecules 2023; 28:4755. [PMID: 37375309 DOI: 10.3390/molecules28124755] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2023] [Revised: 05/23/2023] [Accepted: 06/03/2023] [Indexed: 06/29/2023] Open
Abstract
Non-heme Fe monooxygenases activate C-H bonds using intermediates with high-spin FeIV-oxido centers. To mimic these sites, a new tripodal ligand [pop]3- was prepared that contains three phosphoryl amido groups that are capable of stabilizing metal centers in high oxidation states. The ligand was used to generate [FeIVpop(O)]-, a new FeIV-oxido complex with an S = 2 spin ground state. Spectroscopic measurements, which included low-temperature absorption and electron paramagnetic resonance spectroscopy, supported the assignment of a high-spin FeIV center. The complex showed reactivity with benzyl alcohol as the external substrate but not with related compounds (e.g., ethyl benzene and benzyl methyl ether), suggesting the possibility that hydrogen bonding interaction(s) between the substrate and [FeIVpop(O)]- was necessary for reactivity. These results exemplify the potential role of the secondary coordination sphere in metal-mediated processes.
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Affiliation(s)
- Chen Sun
- Department of Chemistry, University of California-Irvine, Irvine, CA 92697, USA
| | - Jennifer L Jaimes
- Department of Chemistry, University of California-Irvine, Irvine, CA 92697, USA
| | - Alec H Follmer
- Department of Chemistry, University of California-Irvine, Irvine, CA 92697, USA
| | - Joseph W Ziller
- Department of Chemistry, University of California-Irvine, Irvine, CA 92697, USA
| | - Andrew S Borovik
- Department of Chemistry, University of California-Irvine, Irvine, CA 92697, USA
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43
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Török P, Lakk-Bogáth D, Kaizer J. Mechanisms of Sulfoxidation and Epoxidation Mediated by Iron(III)-Iodosylbenzene Adduct: Electron-Transfer vs. Oxygen-Transfer Mechanism. Molecules 2023; 28:4745. [PMID: 37375303 DOI: 10.3390/molecules28124745] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2023] [Revised: 06/12/2023] [Accepted: 06/12/2023] [Indexed: 06/29/2023] Open
Abstract
The mechanisms of sulfoxidation and epoxidation mediated by previously synthesized and characterized iron(III)-iodosylbenzene adduct, FeIII(OIPh) were investigated using para-substituted thioanisole and styrene derivatives as model substrates. Based on detailed kinetic reaction experiments, including the linear free-energy relationships between the relative reaction rates (logkrel) and the σp (4R-PhSMe) with ρ = -0.65 (catalytic) and ρ = -1.13 (stoichiometric), we obtained strong evidence that the stoichiometric and catalytic oxidation of thioanisoles mediated by FeIII(OIPh) species involves direct oxygen transfer. The small negative slope -2.18 from log kobs versus Eox for 4R-PhSMe gives further clear evidence for the direct oxygen atom transfer mechanism. On the contrary, with the linear free-energy relationships between the relative reaction rates (logkrel) and total substituent effect (TE, 4R-PhCHCH2) parameters with slope = 0.33 (catalytic) and 2.02 (stoichiometric), the stoichiometric and catalytic epoxidation of styrenes takes place through a nonconcerted electron transfer (ET) mechanism, including the formation of the radicaloid benzylic radical intermediate in the rate-determining step. On the basis of mechanistic studies, we came to the conclusion that the title iron(III)-iodosylbenzene complex is able to oxygenate sulfides and alkenes before it is transformed into the oxo-iron form by cleavage of the O-I bond.
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Affiliation(s)
- Patrik Török
- Research Group of Bioorganic and Bio-Coordination Chemistry, University of Pannonia, H-8201 Veszprém, Hungary
| | - Dóra Lakk-Bogáth
- Research Group of Bioorganic and Bio-Coordination Chemistry, University of Pannonia, H-8201 Veszprém, Hungary
| | - József Kaizer
- Research Group of Bioorganic and Bio-Coordination Chemistry, University of Pannonia, H-8201 Veszprém, Hungary
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44
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Pan Y, Zhou M, Wang R, Song D, Yiu SM, Xie J, Lau KC, Lau TC, Liu Y. Structure and Reactivity of a Seven-Coordinate Ruthenium Iodosylbenzene Complex. Inorg Chem 2023; 62:7772-7778. [PMID: 37146252 DOI: 10.1021/acs.inorgchem.3c00417] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Seven-coordinate (CN7) ruthenium-oxo species have attracted much attention as highly reactive intermediates in both organic and water oxidation. Apart from metal-oxo, other metal-oxidant adducts, such as metal-iodosylarenes, have also recently emerged as active oxidants. We reported herein the first example of a CN7 Ru-iodosylbenzene complex, [RuIV(bdpm)(pic)2(O)I(Cl)Ph]+ (H2bdpm = [2,2'-bipyridine]-6,6'-diylbis(diphenylmethanol); pic = 4-picoline). The X-ray crystal structure of this complex shows that it adopts a distorted pentagonal bipyramidal geometry with Ru-O(I) and O-I distances of 2.0451(39) and 1.9946(40) Å, respectively. This complex is highly reactive, and it readily undergoes O-atom transfer (OAT) and C-H bond activation reactions with various organic substrates. This work should provide insights for the development of new highly reactive oxidizing agents based on CN7 geometry.
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Affiliation(s)
- Yunling Pan
- Institute of Intelligent Machines, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, P. R. China
- Anhui Province Key Laboratory of Advanced Catalytic Materials and Reaction Engineering, School of Chemistry and Chemical Engineering, Hefei University of Technology, Hefei 230009, P. R. China
| | - Miaomiao Zhou
- Department of Chemistry, City University of Hong Kong, Kowloon Tong 999077, Hong Kong, P. R. China
| | - Rui Wang
- Institute of Intelligent Machines, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, P. R. China
| | - Dan Song
- Institute of Intelligent Machines, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, P. R. China
- Anhui Province Key Laboratory of Advanced Catalytic Materials and Reaction Engineering, School of Chemistry and Chemical Engineering, Hefei University of Technology, Hefei 230009, P. R. China
| | - Shek-Man Yiu
- Department of Chemistry, City University of Hong Kong, Kowloon Tong 999077, Hong Kong, P. R. China
| | - Jianhui Xie
- Anhui Province Key Laboratory of Advanced Catalytic Materials and Reaction Engineering, School of Chemistry and Chemical Engineering, Hefei University of Technology, Hefei 230009, P. R. China
| | - Kai-Chung Lau
- Department of Chemistry, City University of Hong Kong, Kowloon Tong 999077, Hong Kong, P. R. China
| | - Tai-Chu Lau
- Department of Chemistry, City University of Hong Kong, Kowloon Tong 999077, Hong Kong, P. R. China
- Research Center for Eco-environmental Engineering, Dongguan University of Technology, Dongguan 523808, P. R. China
| | - Yingying Liu
- Institute of Intelligent Machines, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031, P. R. China
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45
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Heim P, Spedalotto G, Lovisari M, Gericke R, O'Brien J, Farquhar ER, McDonald AR. Synthesis and Characterization of a Masked Terminal Nickel-Oxide Complex. Chemistry 2023; 29:e202203840. [PMID: 36696360 PMCID: PMC10101870 DOI: 10.1002/chem.202203840] [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: 12/08/2022] [Revised: 01/20/2023] [Accepted: 01/25/2023] [Indexed: 01/26/2023]
Abstract
In exploring terminal nickel-oxo complexes, postulated to be the active oxidant in natural and non-natural oxidation reactions, we report the synthesis of the pseudo-trigonal bipyramidal NiII complexes (K)[NiII (LPh )(DMF)] (1[DMF]) and (NMe4 )2 [NiII (LPh )(OAc)] (1[OAc]) (LPh =2,2',2''-nitrilo-tris-(N-phenylacetamide); DMF=N,N-dimethylformamide; - OAc=acetate). Both complexes were characterized using NMR, FTIR, ESI-MS, and X-ray crystallography, showing the LPh ligand to bind in a tetradentate fashion, together with an ancillary donor. The reaction of 1[OAc] with peroxyphenyl acetic acid (PPAA) resulted in the formation of [(LPh )NiIII -O-H⋅⋅⋅OAc]2- , 2, that displays many of the characteristics of a terminal Ni=O species. 2 was characterized by UV-Vis, EPR, and XAS spectroscopies and ESI-MS. 2 decayed to yield a NiII -phenolate complex 3 (through aromatic electrophilic substitution) that was characterized by NMR, FTIR, ESI-MS, and X-ray crystallography. 2 was capable of hydroxylation of hydrocarbons and epoxidation of olefins, as well as oxygen atom transfer oxidation of phosphines at exceptional rates. While the oxo-wall remains standing, this complex represents an excellent example of a masked metal-oxide that displays all of the properties expected of the ever elusive terminal M=O beyond the oxo-wall.
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Affiliation(s)
- Philipp Heim
- School of Chemistry and CRANN/AMBER Nanoscience Institute, Trinity College Dublin, The University of Dublin, College Green, Dublin 2, Ireland
| | - Giuseppe Spedalotto
- School of Chemistry and CRANN/AMBER Nanoscience Institute, Trinity College Dublin, The University of Dublin, College Green, Dublin 2, Ireland
| | - Marta Lovisari
- School of Chemistry and CRANN/AMBER Nanoscience Institute, Trinity College Dublin, The University of Dublin, College Green, Dublin 2, Ireland
| | - Robert Gericke
- School of Chemistry and CRANN/AMBER Nanoscience Institute, Trinity College Dublin, The University of Dublin, College Green, Dublin 2, Ireland
- Current address: Helmholtz-Zentrum Dresden-Rossendorf e.V., Institute of Resource Ecology, Bautzner Landstraße 400, 01328, Dresden, Germany
| | - John O'Brien
- School of Chemistry and CRANN/AMBER Nanoscience Institute, Trinity College Dublin, The University of Dublin, College Green, Dublin 2, Ireland
| | - Erik R Farquhar
- Center for Synchrotron Biosciences, National Synchrotron Light Source II, Brookhaven, National Laboratory Case Western Reserve University, Upton, NY 11973, USA
| | - Aidan R McDonald
- School of Chemistry and CRANN/AMBER Nanoscience Institute, Trinity College Dublin, The University of Dublin, College Green, Dublin 2, Ireland
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46
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Panda C, Anny-Nzekwue O, Doyle LM, Gericke R, McDonald AR. Evidence for a High-Valent Iron-Fluoride That Mediates Oxidative C(sp 3)-H Fluorination. JACS AU 2023; 3:919-928. [PMID: 37006763 PMCID: PMC10052241 DOI: 10.1021/jacsau.3c00021] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Revised: 02/14/2023] [Accepted: 02/15/2023] [Indexed: 06/19/2023]
Abstract
[FeII(NCCH3)(NTB)](OTf)2 (NTB = tris(2-benzimidazoylmethyl)amine, OTf = trifluoromethanesulfonate) was reacted with difluoro(phenyl)-λ3-iodane (PhIF2) in the presence of a variety of saturated hydrocarbons, resulting in the oxidative fluorination of the hydrocarbons in moderate-to-good yields. Kinetic and product analysis point towards a hydrogen atom transfer oxidation prior to fluorine radical rebound to form the fluorinated product. The combined evidence supports the formation of a formally FeIV(F)2 oxidant that performs hydrogen atom transfer followed by the formation of a dimeric μ-F-(FeIII)2 product that is a plausible fluorine atom transfer rebound reagent. This approach mimics the heme paradigm for hydrocarbon hydroxylation, opening up avenues for oxidative hydrocarbon halogenation.
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47
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Yamada Y, Morita K, Sugiura T, Toyoda Y, Mihara N, Nagasaka M, Takaya H, Tanaka K, Koitaya T, Nakatani N, Ariga-Miwa H, Takakusagi S, Hitomi Y, Kudo T, Tsuji Y, Yoshizawa K, Tanaka K. Stacking of a Cofacially Stacked Iron Phthalocyanine Dimer on Graphite Achieved High Catalytic CH 4 Oxidation Activity Comparable to That of pMMO. JACS AU 2023; 3:823-833. [PMID: 37006766 PMCID: PMC10052267 DOI: 10.1021/jacsau.2c00618] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Revised: 12/29/2022] [Accepted: 12/29/2022] [Indexed: 06/19/2023]
Abstract
Numerous biomimetic molecular catalysts inspired by methane monooxygenases (MMOs) that utilize iron or copper-oxo species as key intermediates have been developed. However, the catalytic methane oxidation activities of biomimetic molecule-based catalysts are still much lower than those of MMOs. Herein, we report that the close stacking of a μ-nitrido-bridged iron phthalocyanine dimer onto a graphite surface is effective in achieving high catalytic methane oxidation activity. The activity is almost 50 times higher than that of other potent molecule-based methane oxidation catalysts and comparable to those of certain MMOs, in an aqueous solution containing H2O2. It was demonstrated that the graphite-supported μ-nitrido-bridged iron phthalocyanine dimer oxidized methane, even at room temperature. Electrochemical investigation and density functional theory calculations suggested that the stacking of the catalyst onto graphite induced partial charge transfer from the reactive oxo species of the μ-nitrido-bridged iron phthalocyanine dimer and significantly lowered the singly occupied molecular orbital level, thereby facilitating electron transfer from methane to the catalyst in the proton-coupled electron-transfer process. The cofacially stacked structure is advantageous for stable adhesion of the catalyst molecule on the graphite surface in the oxidative reaction condition and for preventing decreases in the oxo-basicity and generation rate of the terminal iron-oxo species. We also demonstrated that the graphite-supported catalyst exhibited appreciably enhanced activity under photoirradiation owing to the photothermal effect.
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Affiliation(s)
- Yasuyuki Yamada
- Department
of Chemistry, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya464-8602, Japan
- Research
Center for Materials Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya464-8602, Japan
| | - Kentaro Morita
- Department
of Chemistry, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya464-8602, Japan
| | - Takuya Sugiura
- Department
of Chemistry, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya464-8602, Japan
| | - Yuka Toyoda
- Department
of Chemistry, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya464-8602, Japan
| | - Nozomi Mihara
- Department
of Chemistry, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya464-8602, Japan
| | | | - Hikaru Takaya
- Institute
for Molecular Science, Myodaiji, Okazaki444-8585, Japan
| | - Kiyohisa Tanaka
- Institute
for Molecular Science, Myodaiji, Okazaki444-8585, Japan
| | - Takanori Koitaya
- Institute
for Molecular Science, Myodaiji, Okazaki444-8585, Japan
| | - Naoki Nakatani
- Department
of Chemistry, Graduate School of Science, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji192-0397, Tokyo, Japan
| | - Hiroko Ariga-Miwa
- Institute
for Catalysis, Hokkaido University, Kita 21-10, Kita-ku, Sapporo001-0021, Hokkaido, Japan
| | - Satoru Takakusagi
- Institute
for Catalysis, Hokkaido University, Kita 21-10, Kita-ku, Sapporo001-0021, Hokkaido, Japan
| | - Yutaka Hitomi
- Department
of Molecular Chemistry and Biochemistry, Graduate School of Science
and Engineering, Doshisha University, Kyotanabe610-0321, Kyoto, Japan
| | - Toshiji Kudo
- Daltonics
Division, Bruker Japan K.K., 3-9, Moriya-cho, Kanagawa-ku, Yokohama-shi221-0022, Kanagawa, Japan
| | - Yuta Tsuji
- Institute
for Materials Chemistry and Engineering and IRCCS, Kyushu University, 744
Motooka, Nishi-ku, Fukuoka819-0385, Japan
| | - Kazunari Yoshizawa
- Institute
for Materials Chemistry and Engineering and IRCCS, Kyushu University, 744
Motooka, Nishi-ku, Fukuoka819-0385, Japan
| | - Kentaro Tanaka
- Department
of Chemistry, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya464-8602, Japan
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48
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Schlachta TP, Kühn FE. Cyclic iron tetra N-heterocyclic carbenes: synthesis, properties, reactivity, and catalysis. Chem Soc Rev 2023; 52:2238-2277. [PMID: 36852959 DOI: 10.1039/d2cs01064j] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/01/2023]
Abstract
Cyclic iron tetracarbenes are an emerging class of macrocyclic iron N-heterocyclic carbene (NHC) complexes. They can be considered as an organometallic compound class inspired by their heme analogs, however, their electronic properties differ, e.g. due to the very strong σ-donation of the four combined NHCs in equatorial coordination. The ligand framework of iron tetracarbenes can be readily modified, allowing fine-tuning of the structural and electronic properties of the complexes. The properties of iron tetracarbene complexes are discussed quantitatively and correlations are established. The electronic nature of the tetracarbene ligand allows the isolation of uncommon iron(III) and iron(IV) species and reveals a unique reactivity. Iron tetracarbenes are successfully applied in C-H activation, CO2 reduction, aziridination and epoxidation catalysis and mechanisms as well as decomposition pathways are described. This review will help researchers evaluate the structural and electronic properties of their complexes and target their catalyst properties through ligand design.
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Affiliation(s)
- Tim P Schlachta
- Technical University of Munich, School of Natural Sciences, Department of Chemistry and Catalysis Research Center, Molecular Catalysis, Lichtenbergstraße 4, 85748 Garching, Germany.
| | - Fritz E Kühn
- Technical University of Munich, School of Natural Sciences, Department of Chemistry and Catalysis Research Center, Molecular Catalysis, Lichtenbergstraße 4, 85748 Garching, Germany.
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49
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Surgenor RR, Liu X, Keenlyside MJH, Myers W, Smith MD. Enantioselective synthesis of atropisomeric indoles via iron-catalysed oxidative cross-coupling. Nat Chem 2023; 15:357-365. [PMID: 36509852 DOI: 10.1038/s41557-022-01095-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Accepted: 10/18/2022] [Indexed: 12/14/2022]
Abstract
Heterobiaryl compounds that exhibit axial chirality are of increasing value and interest across several fields, but direct oxidative methods for their enantioselective synthesis remain elusive. Here we disclose that an iron catalyst in the presence of a chiral PyBOX ligand and an oxidant enables direct coupling between naphthols and indoles to yield atropisomeric heterobiaryl compounds with high levels of enantioselectivity. The reaction exhibits remarkable chemoselectivity and exclusively yields cross-coupled products without competing homocoupling. Mechanistic investigations enable us to postulate that an indole radical is generated in the reaction but that this is probably an off-cycle event, and that the reaction proceeds through formation of a chiral Fe-bound naphthoxy radical that is trapped by a nucleophilic indole. We envision that this simple, cheap and sustainable catalytic manifold will facilitate access to a range of heterobiaryl compounds and enable their application across the fields of materials science, medicinal chemistry and catalysis.
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Affiliation(s)
| | - Xiangqian Liu
- Chemistry Research Laboratory, University of Oxford, Oxford, UK
| | | | - William Myers
- Inorganic Chemistry Laboratory, University of Oxford, Oxford, UK
| | - Martin D Smith
- Chemistry Research Laboratory, University of Oxford, Oxford, UK.
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50
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Sarkar S, Shah Tuglak Khan F, Guchhait T, Rath SP. Binuclear complexes with single M-F-M bridge (M: Fe, Mn, and Cu): A critical analysis of the impact of fluoride for isoelectronic hydroxide substitution. Coord Chem Rev 2023. [DOI: 10.1016/j.ccr.2022.215003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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