1
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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. [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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2
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Zhang B, Joyce JP, Wolford NJ, Brennessel WW, DeBeer S, Neidig ML. Unusual S=1 Four-Coordinate Fe(IV) Complexes Supported by Bisamide Ligands: Syntheses, Characterization, and Electronic Structures. Angew Chem Int Ed Engl 2024:e202405113. [PMID: 38864588 DOI: 10.1002/anie.202405113] [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: 03/14/2024] [Revised: 06/11/2024] [Accepted: 06/12/2024] [Indexed: 06/13/2024]
Abstract
The catalytic relevance of Fe(IV) species in non-heme iron catalysis has motivated synthetic advances in well-defined five- and six-coordinate Fe(IV) complexes for a better understanding of their fundamental electronic structures and reactivities. Herein, we report the syntheses of FeDipp2 and FeMes2, a pair of unusual four-coordinate non-heme formally Fe(IV) complexes with S=1 ground states supported by strongly donating bisamide ligands. By combining spectroscopic characterization and computational modeling, we found that small variations in ligand aryl substituents resulted in substantial changes in both structures and bonding. This work highlights the strong donor capabilities and modularity of the bisamide ligand set. More broadly, it is a critical contribution to the utilization of ligand design to modulate molecular geometries and electronic structures of low-coordinate, high-valent iron complexes.
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Affiliation(s)
- Bufan Zhang
- Department of Chemistry, University of Rochester, Hutchison Hall, 120 Trustee Road, 14627, Rochester, NY, United States
- Department of Inorganic Spectroscopy, Max Planck Institute for Chemical Energy Conversion, Stiftstraße 34-36, 45470, Mülheim an der Ruhr, Germany
| | - Justin P Joyce
- Department of Inorganic Spectroscopy, Max Planck Institute for Chemical Energy Conversion, Stiftstraße 34-36, 45470, Mülheim an der Ruhr, Germany
| | - Nikki J Wolford
- Department of Chemistry, University of Rochester, Hutchison Hall, 120 Trustee Road, 14627, Rochester, NY, United States
| | - William W Brennessel
- Department of Chemistry, University of Rochester, Hutchison Hall, 120 Trustee Road, 14627, Rochester, NY, United States
| | - Serena DeBeer
- Department of Inorganic Spectroscopy, Max Planck Institute for Chemical Energy Conversion, Stiftstraße 34-36, 45470, Mülheim an der Ruhr, Germany
| | - Michael L Neidig
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, OX1 3QR, Oxford, United Kingdom
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3
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Bhutto SM, Hooper RX, McWilliams SF, Mercado BQ, Holland PL. Iron(iv) alkyl complexes: electronic structure contributions to Fe-C bond homolysis and migration reactions that form N-C bonds from N 2. Chem Sci 2024; 15:3485-3494. [PMID: 38455018 PMCID: PMC10915813 DOI: 10.1039/d3sc05939a] [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: 11/06/2023] [Accepted: 01/16/2024] [Indexed: 03/09/2024] Open
Abstract
High-valent iron alkyl complexes are rare, as they are prone to Fe-C bond homolysis. Here, we describe an unusual way to access formally iron(iv) alkyl complexes through double silylation of iron(i) alkyl dinitrogen complexes to form an NNSi2 group. Spectroscopically validated computations show that the disilylehydrazido(2-) ligand stabilizes the formal iron(iv) oxidation state through a strongly covalent Fe-N π-interaction, in which one π-bond fits an "inverted field" description. This means that the two bonding electrons are localized more on the metal than the ligand, and thus an iron(ii) resonance structure is a significant contributor, similar to the previously-reported phenyl analogue. However, in contrast to the phenyl complex which has an S = 1 ground state, the ground state of the alkyl complex is S = 2, which places one electron in the π* orbital, leading to longer and weaker Fe-N bonds. The reactivity of these hydrazido(2-) complexes is dependent on the steric and electronic properties of the specific alkyl group. When the alkyl group is the bulky trimethylsilylmethyl, the formally iron(iv) species is stable at room temperature and no migration of the alkyl ligand is observed. However, the analogous complex with the smaller methyl ligand does indeed undergo migration of the carbon-based ligand to the NNSi2 group to form a new N-C bond. This migration is followed by isomerization of the hydrazido ligand, and the product exists as two isomers that have distinct η1 and η2 binding of the hydrazido group. Lastly, when the alkyl group is benzyl, the Fe-C bond homolyzes to give a three-coordinate hydrazido(2-) complex which is likely due to the greater stability of a benzyl radical compared to that for methyl or trimethylsilylmethyl. These studies demonstrate the availability of a hydrocarbyl migration pathway at formally iron(iv) centers to form new N-C bonds directly to N2, though product selectivity is highly dependent on the identity of the migrating group.
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Affiliation(s)
- Samuel M Bhutto
- Department of Chemistry, Yale University New Haven Connecticut 06520 USA
| | - Reagan X Hooper
- Department of Chemistry, Yale University New Haven Connecticut 06520 USA
| | - Sean F McWilliams
- Department of Chemistry, Yale University New Haven Connecticut 06520 USA
| | - Brandon Q Mercado
- Department of Chemistry, Yale University New Haven Connecticut 06520 USA
| | - Patrick L Holland
- Department of Chemistry, Yale University New Haven Connecticut 06520 USA
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4
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Kumar R, Ansari A, Comba P, Rajaraman G. Rebound or Cage Escape? The Role of the Rebound Barrier for the Reactivity of Non-Heme High-Valent Fe IV =O Species. Chemistry 2024; 30:e202303300. [PMID: 37929771 DOI: 10.1002/chem.202303300] [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: 10/09/2023] [Revised: 11/03/2023] [Accepted: 11/06/2023] [Indexed: 11/07/2023]
Abstract
Owing to their high reactivity and selectivity, variations in the spin ground state and a range of possible pathways, high-valent FeIV =O species are popular models with potential bioinspired applications. An interesting example of a structure-reactivity pattern is the detailed study with five nonheme amine-pyridine pentadentate ligand FeIV =O species, including N4py: [(L1 )FeIV =O]2+ (1), bntpen: [(L2 )FeIV =O]2+ (2), py2 tacn: [(L3 )FeIV =O]2+ (3), and two isomeric bispidine derivatives: [(L4 )FeIV =O]2+ (4) and [(L5 )FeIV =O]2+ (5). In this set, the order of increasing reactivity in the hydroxylation of cyclohexane differs from that with cyclohexadiene as substrate. A comprehensive DFT, ab initio CASSCF/NEVPT2 and DLPNO-CCSD(T) study is presented to untangle the observed patterns. These are well reproduced when both activation barriers for the C-H abstraction and the OH rebound are taken into account. An MO, NBO and deformation energy analysis reveals the importance of π(pyr) → π*xz (FeIII -OH) electron donation for weakening the FeIII -OH bond and thus reducing the rebound barrier. This requires that pyridine rings are oriented perpendicularly to the FeIII -OH bond and this is a subtle but crucial point in ligand design for non-heme iron alkane hydroxylation.
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Affiliation(s)
- Ravi Kumar
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai, Powai, 400076, India
| | - Azaj Ansari
- Department of Chemistry, Central University of Haryana, Haryana, 123031, India
| | - Peter Comba
- Institute of Inorganic Chemistry &, Interdisciplinary Center for Scientific Computing, Heidelberg University, 69120, Heidelberg, Germany
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institute of Technology Bombay, Mumbai, Powai, 400076, India
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5
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Mahajan M, Mondal B. Origin of the Distinctive Electronic Structure of Co- and Fe-Porphyrin-Nitrene and Its Effect on Their Nitrene Transfer Reactivity. Inorg Chem 2023; 62:5810-5821. [PMID: 36976917 DOI: 10.1021/acs.inorgchem.3c00463] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/30/2023]
Abstract
Metal-bound nitrene species are the crucial intermediate in catalytic nitrene transfer reactions exhibited by engineered enzymes and molecular catalysts. The electronic structure of such species and its correlation with nitrene transfer reactivity have not been fully understood yet. This work presents an in-depth electronic structure analysis and nitrene transfer reactivity of two prototypical metal-nitrene species derived from CoII(TPP) and FeII(TPP) (TPP = meso-tetraphenylporphyrin) complexes and tosyl azide nitrene precursor. Parallel to the well-known "cobalt(III)-imidyl" electronic structure of the Co-porphyrin-nitrene species, the formation mechanism and electronic structure of the elusive Fe-porphyrin-nitrene have been established using density functional theory (DFT) and multiconfigurational complete active-space self-consistent field (CASSCF) calculations. Electronic structure evolution analysis for the metal-nitrene formation step and CASSCF-derived natural orbitals advocates that the electronic nature of the metal-nitrene (M-N) core of Fe(TPP) is strikingly different from that of the Co(TPP). Specifically, the "imidyl" nature of the Co-porphyrin-nitrene [(TPP)CoIII-•NTos] (Tos = tosyl) (I1Co) is contrasted by the "imido-like" character of the Fe-porphyrin-nitrene [(TPP)FeIV[Formula: see text]NTos] (I1Fe). This difference between Co- and Fe-nitrene has been attributed to the additional interactions between Fe-dπ and N-pπ orbitals in Fe-nitrene, which is further complemented by the shortened Fe-N bond length of 1.71 Å. This stronger M-N bond in Fe-nitrene compared to the Co-nitrene is also reflected in the higher exothermicity (ΔΔH = 16 kcal/mol) of the Fe-nitrene formation step. The "imido-like" character renders a relatively lower spin population on the nitrene nitrogen (+0.42) in the Fe-nitrene complex I1Fe, which undergoes the nitrene transfer to the C═C bond of styrene with a considerably higher enthalpy barrier (ΔH‡ = 10.0 kcal/mol) compared to the Co congener I1Co (ΔH‡ = 5.6 kcal/mol) possessing a higher nitrogen spin population (+0.88) and a relatively weaker M-N bond (Co-N = 1.80 Å).
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Affiliation(s)
- Mayank Mahajan
- 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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6
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Xiong J, Liu Q, Lavina B, Hu MY, Zhao J, Alp EE, Deng L, Ye S, Guo Y. Spin polarization assisted facile C-H activation by an S = 1 iron(iv)-bisimido complex: a comprehensive spectroscopic and theoretical investigation. Chem Sci 2023; 14:2808-2820. [PMID: 36937578 PMCID: PMC10016330 DOI: 10.1039/d2sc06273a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2022] [Accepted: 02/14/2023] [Indexed: 02/17/2023] Open
Abstract
High valent iron terminal imido species (Fe[double bond, length as m-dash]NR) have been shown to be key reactive intermediates in C-H functionalization. However, the detailed structure-reactivity relationship in Fe[double bond, length as m-dash]NR species derived from studies of structurally well-characterized high-valent Fe[double bond, length as m-dash]NR complexes are still scarce, and the impact of imido N-substituents (electron-donating vs. electron-withdrawing) on their electronic structures and reactivities has not been thoroughly explored. In this study, we report spectroscopic and computational studies on a rare S = 1 iron(iv)-bisimido complex featuring trifluoromethyl groups on the imido N-substituents, [(IPr)Fe(NC(CF3)2Ph)2] (2), and two closely related S = 0 congeners bearing alkyl and aryl substituents, [(IPr)Fe(NC(CMe3)2Ph)2] (3) and [(IPr)Fe(NDipp)2] (1), respectively. Compared with 1 and 3, 2 exhibits a decreased Fe[double bond, length as m-dash]NR bond covalency due to the electron-withdrawing and the steric effect of the N-substituents, which further leads to a pseudo doubly degenerate ground electronic structure and spin polarization induced β spin density on the imido nitrogens. This unique electronic structure, which differs from those of the well-studied Fe(iv)-oxido complexes and many previously reported Fe(iv)-imido complexes, provides both kinetic and thermodynamic advantages for facile C-H activation, compared to the S = 0 counterparts.
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Affiliation(s)
- Jin Xiong
- Department of Chemistry, Carnegie Mellon University Pittsburgh Pennsylvania 15213 USA
| | - Qing Liu
- State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences Shanghai 200032 P. R. China
| | - Barbara Lavina
- Advanced Photon Source, Argonne National Laboratory Argonne Illinois 60439 USA
- Center for Advanced Radiation Sources, University of Chicago Chicago Illinois 60439 USA
| | - Michael Y Hu
- Advanced Photon Source, Argonne National Laboratory Argonne Illinois 60439 USA
| | - Jiyong Zhao
- Advanced Photon Source, Argonne National Laboratory Argonne Illinois 60439 USA
| | - Esen E Alp
- Advanced Photon Source, Argonne National Laboratory Argonne Illinois 60439 USA
| | - Liang Deng
- State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences Shanghai 200032 P. R. China
| | - Shengfa Ye
- State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences Dalian 116023 P. R. China
| | - Yisong Guo
- Department of Chemistry, Carnegie Mellon University Pittsburgh Pennsylvania 15213 USA
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7
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Pérez‐Bitrián A, Alvarez S, Baya M, Echeverría J, Martín A, Orduna J, Menjón B. Terminal Au-N and Au-O Units in Organometallic Frames. Chemistry 2023; 29:e202203181. [PMID: 36263870 PMCID: PMC10107225 DOI: 10.1002/chem.202203181] [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: 10/12/2022] [Revised: 10/19/2022] [Accepted: 10/20/2022] [Indexed: 11/06/2022]
Abstract
Since gold is located well beyond the oxo wall, chemical species with terminal Au-N and Au-O units are extremely rare and limited to low coordination numbers. We report here that these unusual units can be trapped within a suitable organometallic frame. Thus, the terminal auronitrene and auroxyl derivatives [(CF3 )3 AuN]- and [(CF3 )3 AuO]- were identified as local minima by calculation. These open-shell, high-energy ions were experimentally detected by tandem mass spectrometry (MS2 ): They respectively arise by N2 or NO2 dissociation from the corresponding precursor species [(CF3 )3 Au(N3 )]- and [(CF3 )3 Au(ONO2 )]- in the gas phase. Together with the known fluoride derivative [(CF3 )3 AuF]- , they form an interesting series of isoleptic and alloelectronic complexes of the highly acidic organogold(iii) moiety (CF3 )3 Au with singly charged anions X- of the most electronegative elements (X=F, O, N). Ligand-field inversion in all these [(CF3 )3 AuX]- species results in the localization of unpaired electrons at the N and O atoms.
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Affiliation(s)
- Alberto Pérez‐Bitrián
- Instituto de Síntesis Química y Catálisis Homogénea (iSQCH)CSIC-Universidad de Zaragoza50009ZaragozaSpain
| | - Santiago Alvarez
- Departament de Química Inorgànica i Orgànica Facultat de QuímicaUniversitat de Barcelona08028BarcelonaSpain
| | - Miguel Baya
- Instituto de Síntesis Química y Catálisis Homogénea (iSQCH)CSIC-Universidad de Zaragoza50009ZaragozaSpain
| | - Jorge Echeverría
- Instituto de Síntesis Química y Catálisis Homogénea (iSQCH)CSIC-Universidad de Zaragoza50009ZaragozaSpain
| | - Antonio Martín
- Instituto de Síntesis Química y Catálisis Homogénea (iSQCH)CSIC-Universidad de Zaragoza50009ZaragozaSpain
| | - Jesús Orduna
- Instituto de Nanociencia y Materiales de Aragón (INMA)CSIC-Universidad de Zaragoza50009ZaragozaSpain
| | - Babil Menjón
- Instituto de Síntesis Química y Catálisis Homogénea (iSQCH)CSIC-Universidad de Zaragoza50009ZaragozaSpain
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8
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Schild DJ, Nurdin L, Moret ME, Oyala PH, Peters JC. Characterization of a Proposed Terminal Iron(III) Nitride Intermediate of Nitrogen Fixation Stabilized by a Trisphosphine-Borane Ligand. Angew Chem Int Ed Engl 2022; 61:e202209655. [PMID: 35973965 PMCID: PMC9588675 DOI: 10.1002/anie.202209655] [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: 07/04/2022] [Indexed: 11/11/2022]
Abstract
Terminal iron nitrides (Fe≡N) have been proposed as intermediates of Fe-mediated nitrogen fixation, and well-defined synthetic iron nitrides have been characterized in high oxidation states, including FeIV , FeV , and FeVI . This study reports the generation and low temperature characterization of a terminally bound iron(III) nitride, P3 B Fe(N) (P3 B =tris(o-diisopropylphosphinophenyl)borane), which is a proposed intermediate of iron-mediated nitrogen fixation by the P3 B Fe-catalyst system. CW- and pulse EPR spectroscopy (HYSCORE and ENDOR), supported by DFT calculations, help to define a 2 A ground state electronic structure of this C3 -symmetric nitride species, placing the unpaired spin in a sigma orbital along the B-Fe-N vector; this electronic structure is distinct for an iron nitride. The unusual d5 -configuration is stabilized by significant delocalization (≈50 %) of the unpaired electron onto the axial boron and nitrogen ligands, with a majority of the spin residing on boron.
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Affiliation(s)
- Dirk J Schild
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Lucie Nurdin
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Marc-Etienne Moret
- Current address: Debye Institute for Nanomaterials Science, Utrecht University, Universiteitsweg 99, 3584 CG, Utrecht, The Netherlands
| | - Paul H Oyala
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Jonas C Peters
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
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9
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Schild DJ, Nurdin L, Moret ME, Oyala PH, Peters J. Characterization of a Proposed Terminal Iron(III) Nitride Intermediate of Nitrogen Fixation Stabilized by a Trisphosphine‐Borane Ligand. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202209655] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Dirk J Schild
- California Institute of Technology Chemistry UNITED STATES
| | - Lucie Nurdin
- California Institute of Technology Chemistry UNITED STATES
| | | | - Paul H Oyala
- California Institute of Technology Chemistry UNITED STATES
| | - Jonas Peters
- California Institute of Technology Division of Chemistry and Chemical Engineering 1200 East California Blvd 91103 Pasadena UNITED STATES
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10
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Cordes Née Kupper C, Klawitter I, Rüter I, Dechert S, Demeshko S, Ye S, Meyer F. Organometallic μ-Nitridodiiron Complexes in Oxidation States Ranging from (III/III) to (IV/IV). Inorg Chem 2022; 61:7153-7164. [PMID: 35475617 DOI: 10.1021/acs.inorgchem.2c00685] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Iron complexes with nitrido ligands are of interest as molecular analogues of key intermediates during N2-to-NH3 conversion in industrial or enzymatic processes. Dinuclear iron complexes with a bridging nitrido unit are mostly known in relatively high oxidation states (III/IV or IV/IV), originating from the decomposition of azidoiron precursors via high-valent Fe≡N intermediates. The use of a tetra-NHC macrocyclic scaffold ligand (NHC = N-heterocyclic carbene) has now allowed for the isolation of a series of organometallic μ-nitridodiiron complexes ranging from the mid-valent FeIII-N-FeIII (1) via mixed-valent FeIII-N-FeIV (type 4) to the high-valent FeIV-N-FeIV (type 5) species that are interconverted at moderate potentials, accompanied by axial ligand binding at the FeIV sites. Magnetic measurements and electron paramagnetic resonance spectroscopy showed the homovalent complexes to be diamagnetic and the mixed-valent system to feature an S = 1/2 ground state due to very strong antiferromagnetic coupling. The bonding in the Fe-N-Fe moiety has been further probed by crystallographic structure determination, 57Fe Mössbauer and UV-vis spectroscopies, as well as density functional theory computations, which revealed high covalency and nearly identical Fe-N distances across this redox series. The latter has been rationalized in terms of the nonbonding nature of the combination of Fe dz2 atomic orbitals from which electrons are successively removed upon oxidation, and these redox processes are best described as being metal-centered. The tetra-NHC-ligated μ-nitridodiiron series complements a set of related complexes with single-atom μ-oxido and μ-phosphido bridges, but the Fe-N-Fe core exhibits a comparatively high stability over several oxidation states. This promises interesting applications in view of the manifold catalytic uses of μ-nitridodiiron complexes based on macrocyclic N-donor porphinato(2-) or phthalocyaninato(2-) ligands.
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Affiliation(s)
- Claudia Cordes Née Kupper
- Institute of Inorganic Chemistry, University of Göttingen, Tammannstrasse 4, D-37077 Göttingen, Germany
| | - Iris Klawitter
- Institute of Inorganic Chemistry, University of Göttingen, Tammannstrasse 4, D-37077 Göttingen, Germany
| | - Isabelle Rüter
- Institute of Inorganic Chemistry, University of Göttingen, Tammannstrasse 4, D-37077 Göttingen, Germany
| | - Sebastian Dechert
- Institute of Inorganic Chemistry, University of Göttingen, Tammannstrasse 4, D-37077 Göttingen, Germany
| | - Serhiy Demeshko
- Institute of Inorganic Chemistry, University of Göttingen, Tammannstrasse 4, D-37077 Göttingen, Germany
| | - Shengfa Ye
- State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, People's Republic of China
| | - Franc Meyer
- Institute of Inorganic Chemistry, University of Göttingen, Tammannstrasse 4, D-37077 Göttingen, Germany
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11
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Ng R, Ng WM, Cheung WM, Sung HHY, Williams ID, Leung WH. Heterometallic iron(IV) μ-nitrido complexes supported by a tetradentate Schiff base ligand. J Organomet Chem 2022. [DOI: 10.1016/j.jorganchem.2022.122354] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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12
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Li Y, Chen JY, Miao Q, Yu X, Feng L, Liao RZ, Ye S, Tung CH, Wang W. A Parent Iron Amido Complex in Catalysis of Ammonia Oxidation. J Am Chem Soc 2022; 144:4365-4375. [PMID: 35234468 DOI: 10.1021/jacs.1c08609] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Parent amido complexes are crucial intermediates in ammonia-based transformations. We report a well-defined ferric ammine system [Cp*Fe(1,2-Ph2PC6H4NH)(NH3)]+ ([1-NH3]+), which processes electrocatalytic ammonia oxidation to N2 and H2 at a mild potential. Through establishing elementary e-/H+ conversions with the ferric ammine, a formal Fe(IV)-amido species, [1-NH2]+, together with its conjugated Lewis acid, [1-NH3]2+, was isolated and structurally characterized for the first time. Mechanism studies indicated that further oxidation of [1-NH2]+ induces the reaction of the parent amido unit with NH3. The formation of hydrazine is realized by the non-innocent nature of the phenylamido ligand that facilitates the concerted transfer of one proton and two electrons.
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Affiliation(s)
- Yongxian Li
- School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, China
| | - Jia-Yi Chen
- School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Qiyi Miao
- State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China.,University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xin Yu
- School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, China
| | - Lei Feng
- School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, China
| | - Rong-Zhen Liao
- School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
| | - Shengfa Ye
- State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China.,Max-Planck-Institut für Kohlenforschung, D-45470 Mülheim an der Ruhr, Germany
| | - Chen-Ho Tung
- School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, China
| | - Wenguang Wang
- School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, China.,College of Chemistry, Beijing Normal University, Beijing 100875, China
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13
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Stüker T, Xia X, Beckers H, Riedel S. High-Spin Iron(VI), Low-Spin Ruthenium(VI), and Magnetically Bistable Osmium(VI) in Molecular Group 8 Nitrido Trifluorides NMF 3. Chemistry 2021; 27:11693-11700. [PMID: 34043842 PMCID: PMC8457171 DOI: 10.1002/chem.202101404] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Indexed: 12/15/2022]
Abstract
Pseudo‐tetrahedral nitrido trifluorides N≡MF3 (M=Fe, Ru, Os) and square pyramidal nitrido tetrafluorides N≡MF4 (M=Ru, Os) were formed by free‐metal‐atom reactions with NF3 and subsequently isolated in solid neon at 5 K. Their IR spectra were recorded and analyzed aided by quantum‐chemical calculations. For a d2 electron configuration of the N≡MF3 compounds in C3v symmetry, Hund's rule predict a high‐spin 3A2 ground state with two parallel spin electrons and two degenerate metal d(δ)‐orbitals. The corresponding high‐spin 3A2 ground state was, however, only found for N≡FeF3, the first experimentally verified neutral nitrido FeVI species. The valence‐isoelectronic N≡RuF3 and N≡OsF3 adopt different angular distorted singlet structures. For N≡RuF3, the triplet 3A2 state is only 5 kJ mol−1 higher in energy than the singlet 1A′ ground state, and the magnetically bistable molecular N≡OsF3 with two distorted near degenerate 1A′ and 3A“ electronic states were experimentally detected at 5 K in solid neon.
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Affiliation(s)
- Tony Stüker
- Institut für Chemie und Biochemie, Anorganische Chemie, Freie Universität Berlin, Fabeckstr. 34/36, 14195, Berlin, Germany
| | - Xiya Xia
- Institut für Chemie und Biochemie, Anorganische Chemie, Freie Universität Berlin, Fabeckstr. 34/36, 14195, Berlin, Germany
| | - Helmut Beckers
- Institut für Chemie und Biochemie, Anorganische Chemie, Freie Universität Berlin, Fabeckstr. 34/36, 14195, Berlin, Germany
| | - Sebastian Riedel
- Institut für Chemie und Biochemie, Anorganische Chemie, Freie Universität Berlin, Fabeckstr. 34/36, 14195, Berlin, Germany
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14
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Schulz CE, Castillo RG, Pantazis DA, DeBeer S, Neese F. Structure-Spectroscopy Correlations for Intermediate Q of Soluble Methane Monooxygenase: Insights from QM/MM Calculations. J Am Chem Soc 2021; 143:6560-6577. [PMID: 33884874 PMCID: PMC8154522 DOI: 10.1021/jacs.1c01180] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
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The determination
of the diiron core intermediate structures involved
in the catalytic cycle of soluble methane monooxygenase (sMMO), the
enzyme that selectively catalyzes the conversion of methane to methanol,
has been a subject of intense interest within the bioinorganic scientific
community. Particularly, the specific geometry and electronic structure
of the intermediate that precedes methane binding, known as intermediate
Q (or MMOHQ), has been debated for over 30 years. Some
reported studies support a bis-μ-oxo-bridged Fe(IV)2O2 closed-core conformation Fe(IV)2O2 core, whereas others favor an open-core geometry, with a longer
Fe–Fe distance. The lack of consensus calls for a thorough
re-examination and reinterpretation of the spectroscopic data available
on the MMOHQ intermediate. Herein, we report extensive
simulations based on a hybrid quantum mechanics/molecular mechanics
approach (QM/MM) approach that takes into account the complete enzyme
to explore possible conformations for intermediates MMOHox and MMOHQ of the sMMOH catalytic cycle. High-level quantum
chemical approaches are used to correlate specific structural motifs
with geometric parameters for comparison with crystallographic and
EXAFS data, as well as with spectroscopic data from Mössbauer
spectroscopy, Fe K-edge high-energy resolution X-ray absorption spectroscopy
(HERFD XAS), and resonance Raman 16O–18O difference spectroscopy. The results provide strong support for
an open-core-type configuration in MMOHQ, with the most
likely topology involving mono-oxo-bridged Fe ions and alternate terminal
Fe-oxo and Fe-hydroxo groups that interact via intramolecular hydrogen
bonding. The implications of an open-core intermediate Q on the reaction
mechanism of sMMO are discussed.
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Affiliation(s)
- Christine E Schulz
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr, Germany
| | - Rebeca G Castillo
- Max Planck Institute for Chemical Energy Conversion, Stiftstr. 34-36, 45470 Mülheim an der Ruhr, Germany
| | - Dimitrios A Pantazis
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr, Germany
| | - Serena DeBeer
- Max Planck Institute for Chemical Energy Conversion, Stiftstr. 34-36, 45470 Mülheim an der Ruhr, Germany
| | - Frank Neese
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr, Germany
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15
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Wang H, Wu L, Zheng B, Du L, To W, Ko C, Phillips DL, Che C. C−H Activation by an Iron‐Nitrido Bis‐Pocket Porphyrin Species. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202014191] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Affiliation(s)
- Hai‐Xu Wang
- State Key Laboratory of Synthetic Chemistry and Department of Chemistry The University of Hong Kong Pokfulam Road Hong Kong China
| | - Liangliang Wu
- State Key Laboratory of Synthetic Chemistry and Department of Chemistry The University of Hong Kong Pokfulam Road Hong Kong China
| | - Bin Zheng
- State Key Laboratory of Synthetic Chemistry and Department of Chemistry The University of Hong Kong Pokfulam Road Hong Kong China
| | - Lili Du
- State Key Laboratory of Synthetic Chemistry and Department of Chemistry The University of Hong Kong Pokfulam Road Hong Kong China
| | - Wai‐Pong To
- State Key Laboratory of Synthetic Chemistry and Department of Chemistry The University of Hong Kong Pokfulam Road Hong Kong China
| | - Cheng‐Hoi Ko
- State Key Laboratory of Synthetic Chemistry and Department of Chemistry The University of Hong Kong Pokfulam Road Hong Kong China
| | - David Lee Phillips
- State Key Laboratory of Synthetic Chemistry and Department of Chemistry The University of Hong Kong Pokfulam Road Hong Kong China
| | - Chi‐Ming Che
- State Key Laboratory of Synthetic Chemistry and Department of Chemistry The University of Hong Kong Pokfulam Road Hong Kong China
- HKU Shenzhen Institute of Research & Innovation Shenzhen China
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16
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Wang HX, Wu L, Zheng B, Du L, To WP, Ko CH, Phillips DL, Che CM. C-H Activation by an Iron-Nitrido Bis-Pocket Porphyrin Species. Angew Chem Int Ed Engl 2021; 60:4796-4803. [PMID: 33205509 DOI: 10.1002/anie.202014191] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2020] [Revised: 11/16/2020] [Indexed: 12/11/2022]
Abstract
High-valent iron-nitrido species are nitrogen analogues of iron-oxo species which are versatile reagents for C-H oxidation. Nonetheless, C-H activation by iron-nitrido species has been scarcely explored, as this is often hampered by their instability and short lifetime in solutions. Herein, the hydrogen atom transfer (HAT) reactivity of an Fe porphyrin nitrido species (2 c) toward C-H substrates was studied in solutions at room temperature, which was achieved by nanosecond laser flash photolysis (LFP) of its FeIII -azido precursor (1 c) supported by a bulky bis-pocket porphyrin ligand. C-H bonds with bond dissociation enthalpies (BDEs) of up to ≈84 kcal mol-1 could be activated, and the second-order rate constants (k2 ) are on the order of 102 -104 s-1 m-1 . The Fe-amido product formed after HAT could further release ammonia upon protonation.
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Affiliation(s)
- Hai-Xu Wang
- State Key Laboratory of Synthetic Chemistry and Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, China
| | - Liangliang Wu
- State Key Laboratory of Synthetic Chemistry and Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, China
| | - Bin Zheng
- State Key Laboratory of Synthetic Chemistry and Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, China
| | - Lili Du
- State Key Laboratory of Synthetic Chemistry and Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, China
| | - Wai-Pong To
- State Key Laboratory of Synthetic Chemistry and Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, China
| | - Cheng-Hoi Ko
- State Key Laboratory of Synthetic Chemistry and Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, China
| | - David Lee Phillips
- State Key Laboratory of Synthetic Chemistry and Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, China
| | - Chi-Ming Che
- State Key Laboratory of Synthetic Chemistry and Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, China.,HKU Shenzhen Institute of Research & Innovation, Shenzhen, China
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17
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Roy L. Theoretical Identification of the Factors Governing the Reactivity of C-H Bond Activation by Non-Heme Iron(IV)-Oxo Complexes. Chempluschem 2020; 84:893-906. [PMID: 31943994 DOI: 10.1002/cplu.201900178] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2019] [Revised: 05/30/2019] [Indexed: 11/06/2022]
Abstract
Selective functionalization of C-H bonds provides a straightforward approach to a large variety of well-defined derivatives. High-valent mononuclear iron(IV)-oxo complexes are proposed to carry out these C-H activation reactions in enzymes or in biomimetic syntheses. In this Minireview, we aim to highlight the features that delineate the distinct reactivity of non-heme oxo-iron(IV) motifs to cleave strong C-H bonds in hydrocarbons, primarily focusing on the hydrogen atom transfer (HAT) process. We describe how the structural and electronic properties of supporting ligands modulate the oxidative property of the iron(IV)-oxo complexes. Furthermore, we highlight the decisive role played by spin-state in these biomimetic reactions. We also discuss how tunneling and external perturbations like electric field influence the transfer of hydrogen atoms. Lastly, we emphasize how computations could work as a practical guide to sketch and develop synthetic models with greater efficacy.
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Affiliation(s)
- Lisa Roy
- Institute of Chemical Technology Mumbai IOC Odisha Campus Bhubaneswar, IIT Kharagpur Extension Centre, Bhubaneswar, 751013, Odisha, India
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18
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Ricciarelli D, Belpassi L, Harvey JN, Belanzoni P. Spin-Forbidden Reactivity of Transition Metal Oxo Species: Exploring the Potential Energy Surfaces. Chemistry 2020; 26:3080-3089. [PMID: 31846105 DOI: 10.1002/chem.201904314] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2019] [Indexed: 11/06/2022]
Abstract
Spin-forbidden reactions are frequently encountered when transition metal oxo species are involved, particularly in oxygen transfer reactivity. The computational study of such reactions is challenging, because reactants and products are located on different spin potential energy surfaces (PESs). One possible approach to describe these reactions is the so-called minimum energy crossing point (MECP) between the diabatic reactants and products PESs. Alternatively, inclusion of spin-orbit coupling (SOC) effects allows to locate a saddle point on a single adiabatic PES (TS SOC). The TS SOC approach is rarely applied because of its high computational cost. Recently evidence for a TS SOC impact on significantly lowering the activation barrier in dioxygen addition to a carbene-gold(I)-hydride complex reaction (Chem. Sci. 2016, 7, 7034-7039) or even on predicting a qualitatively different reaction mechanism in mercury methylation by cobalt corrinoid (Angew. Chem. Int. Ed. 2016, 55, 11503-11506) has been put forward. Using MECP and TS SOC approaches a systematic analysis is provided here of three prototypical transition metal oxo spin-forbidden processes to investigate their implications on reactivity. Cycloaddition of ethylene to chromyl chloride (CrO2 Cl2 +C2 H4 ), iron oxide cation insertion into the hydrogen molecule (FeO+ +H2 ) and H-abstraction from toluene by a MnV -oxo-porphyrin cation (MnOP(H2 O)+ +C6 H5 CH3 ) are case studies. For all these processes the MECP and TS SOC results are compared, which show that the spin-forbidden reactivity of transition metal oxo species can be safely described by a MECP approach, at least for the first-row transition metals investigated here, where the spin-orbit coupling is relatively weak. However, for the Mn-oxo reactivity, the MECP and TS SOC have been found to be crucial for a correct description of the reaction mechanism. In particular, the TS SOC approach allows to straightforwardly explore detailed features of the adiabatic potential energy surface which in principle could affect the overall reaction rate in cases where the involved diabatic PESs are tricky.
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Affiliation(s)
- Damiano Ricciarelli
- Department of Chemistry, Biology and Biotechnology, University of Perugia, via Elce di Sotto 8, 06123, Perugia, Italy
| | - Leonardo Belpassi
- CNR Institute of Chemical Science and Technologies "Giulio Natta" (CNR-SCITEC), via Elce di Sotto 8, 06123, Perugia, Italy.,Consortium for Computational Molecular and Materials Sciences (CMS)2, via Elce di Sotto 8, 06123, Perugia, Italy
| | - Jeremy N Harvey
- Department of Chemistry, KU Leuven, Celestijnenlaan 200F, 3001, Leuven, Belgium
| | - Paola Belanzoni
- Department of Chemistry, Biology and Biotechnology, University of Perugia, via Elce di Sotto 8, 06123, Perugia, Italy.,CNR Institute of Chemical Science and Technologies "Giulio Natta" (CNR-SCITEC), via Elce di Sotto 8, 06123, Perugia, Italy.,Consortium for Computational Molecular and Materials Sciences (CMS)2, via Elce di Sotto 8, 06123, Perugia, Italy
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19
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Lu X, Li XX, Lee YM, Jang Y, Seo MS, Hong S, Cho KB, Fukuzumi S, Nam W. Electron-Transfer and Redox Reactivity of High-Valent Iron Imido and Oxo Complexes with the Formal Oxidation States of Five and Six. J Am Chem Soc 2020; 142:3891-3904. [DOI: 10.1021/jacs.9b11682] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Affiliation(s)
- Xiaoyan Lu
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
| | - Xiao-Xi Li
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
| | - Yong-Min Lee
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
| | - Yuri Jang
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
| | - Mi Sook Seo
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
| | - Seungwoo Hong
- Department of Chemistry, Sookmyung Women’s University, Seoul 04310, Korea
| | - Kyung-Bin Cho
- Department of Chemistry, Jeonbuk National University, Jeonju 54896, Korea
| | - Shunichi Fukuzumi
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
- Graduate School of Science and Engineering, Meijo University, Nagoya, Aichi 468-8502, Japan
| | - Wonwoo Nam
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
- Institute of Drug Discovery Technology, Ningbo University, Ningbo 315211, China
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20
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Citek C, Oyala PH, Peters JC. Mononuclear Fe(I) and Fe(II) Acetylene Adducts and Their Reductive Protonation to Terminal Fe(IV) and Fe(V) Carbynes. J Am Chem Soc 2019; 141:15211-15221. [PMID: 31430146 PMCID: PMC6800224 DOI: 10.1021/jacs.9b06987] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The activity of nitrogenase enzymes, which catalyze the conversion of atmospheric dinitrogen to bioavailable ammonia, is most commonly assayed by the reduction of acetylene gas to ethylene. Despite the practical importance of acetylene as a substrate, little is known concerning its binding or activation in the iron-rich active site. "Fischer-Tropsch" type coupling of non-native C1 substrates to higher-order C≥2 products is also known for nitrogenase, though potential metal-carbon multiply bonded intermediates remain underexplored. Here we report the activation of acetylene gas at a mononuclear tris(phosphino)silyl-iron center, (SiP3)Fe, to give Fe(I) and Fe(II) side-on adducts, including S = 1/2 FeI(η2-HCCH); the latter is characterized by pulse EPR spectroscopy and DFT calculations. Reductive protonation reactions with these compounds converge at stable examples of unusual, formally iron(IV) and iron(V) carbyne complexes, as in diamagnetic (SiP3)Fe≡CCH3 and the paramagnetic cation S = 1/2 [(SiP3)Fe≡CCH3]+. Both alkylcarbyne compounds possess short Fe-C triple bonds (approximately 1.7 Å) trans to the anchoring silane. Pulse EPR experiments, X-band ENDOR and HYSCORE, reveal delocalization of the iron-based spin onto the α-carbyne nucleus in carbon p-orbitals. Furthermore, isotropic coupling of the distal β-CH3 protons with iron indicates hyperconjugation with the spin/hole character on the Fe≡CCH3 unit. The electronic structures of (SiP3)Fe≡CCH3 and [(SiP3)Fe≡CCH3]+ are discussed in comparison to previously characterized, but heterosubstituted, iron carbynes, as well as a hypothetical nitride species, (SiP3)Fe≡N. Such comparisons are germane to the consideration of formally high-valent, multiply bonded Fe≡C and/or Fe≡N intermediates in synthetic or biological catalysis by iron.
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Affiliation(s)
- Cooper Citek
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Paul H. Oyala
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Jonas C. Peters
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
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21
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Andris E, Navrátil R, Jašík J, Srnec M, Rodríguez M, Costas M, Roithová J. M-O Bonding Beyond the Oxo Wall: Spectroscopy and Reactivity of Cobalt(III)-Oxyl and Cobalt(III)-Oxo Complexes. Angew Chem Int Ed Engl 2019; 58:9619-9624. [PMID: 31083766 PMCID: PMC6618258 DOI: 10.1002/anie.201904546] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Revised: 05/13/2019] [Indexed: 01/05/2023]
Abstract
Terminal oxo complexes of late transition metals are frequently proposed reactive intermediates. However, they are scarcely known beyond Group 8. Using mass spectrometry, we prepared and characterized two such complexes: [(N4Py)CoIII (O)]+ (1) and [(N4Py)CoIV (O)]2+ (2). Infrared photodissociation spectroscopy revealed that the Co-O bond in 1 is rather strong, in accordance with its lack of chemical reactivity. On the contrary, 2 has a very weak Co-O bond characterized by a stretching frequency of ≤659 cm-1 . Accordingly, 2 can abstract hydrogen atoms from non-activated secondary alkanes. Previously, this reactivity has only been observed in the gas phase for small, coordinatively unsaturated metal complexes. Multireference ab-initio calculations suggest that 2, formally a cobalt(IV)-oxo complex, is best described as cobalt(III)-oxyl. Our results provide important data on changes to metal-oxo bonding behind the oxo wall and show that cobalt-oxo complexes are promising targets for developing highly active C-H oxidation catalysts.
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Affiliation(s)
- Erik Andris
- Department of Organic ChemistryFaculty of ScienceCharles UniversityHlavova 2030/8128 43Prague 2Czech Republic
| | - Rafael Navrátil
- Department of Organic ChemistryFaculty of ScienceCharles UniversityHlavova 2030/8128 43Prague 2Czech Republic
| | - Juraj Jašík
- Department of Organic ChemistryFaculty of ScienceCharles UniversityHlavova 2030/8128 43Prague 2Czech Republic
| | - Martin Srnec
- J. Heyrovsky Institute of Physical Chemistry of the CASv. v. i., Dolejškova 2155/31822 3Prague 8Czech Republic
| | - Mònica Rodríguez
- Departament de Quimica and Institute of Computational Chemistry and Catalysis (IQCC)University of GironaCampus MontiliviGirona17071Spain
| | - Miquel Costas
- Departament de Quimica and Institute of Computational Chemistry and Catalysis (IQCC)University of GironaCampus MontiliviGirona17071Spain
| | - Jana Roithová
- Department of Organic ChemistryFaculty of ScienceCharles UniversityHlavova 2030/8128 43Prague 2Czech Republic
- Radboud University NijmegenInstitute for Molecules and MaterialsHeyendaalseweg 1356525 AJNijmegenThe Netherlands
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22
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Andris E, Navrátil R, Jašík J, Srnec M, Rodríguez M, Costas M, Roithová J. M−O Bonding Beyond the Oxo Wall: Spectroscopy and Reactivity of Cobalt(III)‐Oxyl and Cobalt(III)‐Oxo Complexes. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201904546] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Erik Andris
- Department of Organic ChemistryFaculty of ScienceCharles University Hlavova 2030/8 128 43 Prague 2 Czech Republic
| | - Rafael Navrátil
- Department of Organic ChemistryFaculty of ScienceCharles University Hlavova 2030/8 128 43 Prague 2 Czech Republic
| | - Juraj Jašík
- Department of Organic ChemistryFaculty of ScienceCharles University Hlavova 2030/8 128 43 Prague 2 Czech Republic
| | - Martin Srnec
- J. Heyrovsky Institute of Physical Chemistry of the CAS v. v. i., Dolejškova 2155/3 1822 3 Prague 8 Czech Republic
| | - Mònica Rodríguez
- Departament de Quimica and Institute of Computational Chemistry and Catalysis (IQCC)University of Girona Campus Montilivi Girona 17071 Spain
| | - Miquel Costas
- Departament de Quimica and Institute of Computational Chemistry and Catalysis (IQCC)University of Girona Campus Montilivi Girona 17071 Spain
| | - Jana Roithová
- Department of Organic ChemistryFaculty of ScienceCharles University Hlavova 2030/8 128 43 Prague 2 Czech Republic
- Radboud University NijmegenInstitute for Molecules and Materials Heyendaalseweg 135 6525 AJ Nijmegen The Netherlands
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23
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Bae SH, Li XX, Seo MS, Lee YM, Fukuzumi S, Nam W. Tunneling Controls the Reaction Pathway in the Deformylation of Aldehydes by a Nonheme Iron(III)–Hydroperoxo Complex: Hydrogen Atom Abstraction versus Nucleophilic Addition. J Am Chem Soc 2019; 141:7675-7679. [DOI: 10.1021/jacs.9b02272] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- Seong Hee Bae
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
| | - Xiao-Xi Li
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
| | - Mi Sook Seo
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
| | - Yong-Min Lee
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
| | - Shunichi Fukuzumi
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
- Faculty of Science and Engineering, Meijo University, SENTAN, Japan Science and Technology Agency (JST), Nagoya, Aichi 468-8502, Japan
| | - Wonwoo Nam
- Department of Chemistry and Nano Science, Ewha Womans University, Seoul 03760, Korea
- State Key Laboratory for Oxo Synthesis and Selective Oxidation, Suzhou Research Institute of LICP, Lanzhou Institute of Chemical Physics (LICP), Chinese Academy of Sciences, Lanzhou 730000, China
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24
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Chang HC, Mondal B, Fang H, Neese F, Bill E, Ye S. Electron Paramagnetic Resonance Signature of Tetragonal Low Spin Iron(V)-Nitrido and -Oxo Complexes Derived from the Electronic Structure Analysis of Heme and Non-Heme Archetypes. J Am Chem Soc 2019; 141:2421-2434. [PMID: 30620571 PMCID: PMC6728100 DOI: 10.1021/jacs.8b11429] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
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Iron(V)-nitrido and -oxo complexes
have been proposed as key intermediates
in a diverse array of chemical transformations. Herein we present
a detailed electronic-structure analysis of [FeV(N)(TPP)]
(1, TPP2– = tetraphenylporphyrinato),
and [FeV(N)(cyclam-ac)]+ (2, cyclam-ac
= 1,4,8,11-tetraazacyclotetradecane-1-acetato) using electron paramagnetic
resonance (EPR) and 57Fe Mössbauer spectroscopy
coupled with wave function based complete active-space self-consistent
field (CASSCF) calculations. The findings were compared with all other
well-characterized genuine iron(V)-nitrido and -oxo complexes, [FeV(N)(MePy2tacn)](PF6)2 (3, MePy2tacn = methyl-N′,N″-bis(2-picolyl)-1,4,7-triazacyclononane), [FeV(N){PhB(t-BuIm)3}]+ (4, PhB(tBuIm)3– = phenyltris(3-tert-butylimidazol-2-ylidene)borate),
and [FeV(O)(TAML)]− (5,
TAML4– = tetraamido macrocyclic ligand). Our results
revealed that complex 1 is an authenticated iron(V)-nitrido
species and contrasts with its oxo congener, compound I, which contains
a ferryl unit interacting with a porphyrin radical. More importantly,
tetragonal iron(V)-nitrido and -oxo complexes 1–3 and 5 all possess an orbitally nearly doubly
degenerate S = 1/2 ground state. Consequently, analogous
near-axial EPR spectra with g|| < g⊥ ≤ 2 were measured for them,
and their g|| and g⊥ values were found to obey a simple relation of g⊥2 + (2 – g∥)2 = 4. However, the bonding situation for trigonal iron(V)-nitrido
complex 4 is completely different as evidenced by its
distinct EPR spectrum with g|| < 2
< g⊥. Further in-depth analyses
suggested that tetragonal low spin iron(V)-nitrido and -oxo complexes
feature electronic structures akin to those found for complexes 1–3 and 5. Therefore, the
characteristic EPR signals determined for 1–3 and 5 can be used as a spectroscopic marker
to identify such highly reactive intermediates in catalytic processes.
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Affiliation(s)
- Hao-Ching Chang
- Max-Planck-Institut für Kohlenforschung , Kaiser-Wilhelm-Platz 1 , D-45470 Mülheim an der Ruhr , Germany
| | - Bhaskar Mondal
- Max-Planck-Institut für Chemische Energiekonversion , Stiftstr. 34-36 , D-45470 Mülheim an der Ruhr , Germany
| | - Huayi Fang
- Max-Planck-Institut für Chemische Energiekonversion , Stiftstr. 34-36 , D-45470 Mülheim an der Ruhr , Germany
| | - Frank Neese
- Max-Planck-Institut für Kohlenforschung , Kaiser-Wilhelm-Platz 1 , D-45470 Mülheim an der Ruhr , Germany
| | - Eckhard Bill
- Max-Planck-Institut für Chemische Energiekonversion , Stiftstr. 34-36 , D-45470 Mülheim an der Ruhr , Germany
| | - Shengfa Ye
- Max-Planck-Institut für Kohlenforschung , Kaiser-Wilhelm-Platz 1 , D-45470 Mülheim an der Ruhr , Germany
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25
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Roy L, Al-Afyouni MH, DeRosha DE, Mondal B, DiMucci IM, Lancaster KM, Shearer J, Bill E, Brennessel WW, Neese F, Ye S, Holland PL. Reduction of CO 2 by a masked two-coordinate cobalt(i) complex and characterization of a proposed oxodicobalt(ii) intermediate. Chem Sci 2019; 10:918-929. [PMID: 30774886 PMCID: PMC6346294 DOI: 10.1039/c8sc02599a] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Accepted: 10/22/2018] [Indexed: 12/31/2022] Open
Abstract
Fixation and chemical reduction of CO2 are important for utilization of this abundant resource, and understanding the detailed mechanism of C-O cleavage is needed for rational development of CO2 reduction methods. Here, we describe a detailed analysis of the mechanism of the reaction of a masked two-coordinate cobalt(i) complex, L tBuCo (where L tBu = 2,2,6,6-tetramethyl-3,5-bis[(2,6-diisopropylphenyl)imino]hept-4-yl), with CO2, which yields two products of C-O cleavage, the cobalt(i) monocarbonyl complex L tBuCo(CO) and the dicobalt(ii) carbonate complex (L tBuCo)2(μ-CO3). Kinetic studies and computations show that the κN,η6-arene isomer of L tBuCo rearranges to the κ2 N,N' binding mode prior to binding of CO2, which contrasts with the mechanism of binding of other substrates to L tBuCo. Density functional theory (DFT) studies show that the only low-energy pathways for cleavage of CO2 proceed through bimetallic mechanisms, and DFT and highly correlated domain-based local pair natural orbital coupled cluster (DLPNO-CCSD(T)) calculations reveal the cooperative effects of the two metal centers during facile C-O bond rupture. A plausible intermediate in the reaction of CO2 with L tBuCo is the oxodicobalt(ii) complex L tBuCoOCoL tBu, which has been independently synthesized through the reaction of L tBuCo with N2O. The rapid reaction of L tBuCoOCoL tBu with CO2 to form the carbonate product indicates that the oxo species is kinetically competent to be an intermediate during CO2 cleavage by L tBuCo. L tBuCoOCoL tBu is a novel example of a thoroughly characterized molecular cobalt-oxo complex where the cobalt ions are clearly in the +2 oxidation state. Its nucleophilic reactivity is a consequence of high charge localization on the μ-oxo ligand between two antiferromagnetically coupled high-spin cobalt(ii) centers, as characterized by DFT and multireference complete active space self-consistent field (CASSCF) calculations.
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Affiliation(s)
- Lisa Roy
- Max Planck Institute for Chemical Energy Conversion , Stiftstraße 34-36 , Mülheim an der Ruhr , D-45470 , Germany
- CSIR Central Mechanical Engineering Research Institute , Durgapur 713209 , India
| | - Malik H Al-Afyouni
- Department of Chemistry , University of Rochester , Rochester , New York 14618 , USA
| | - Daniel E DeRosha
- Department of Chemistry , Yale University , New Haven , Connecticut 06520 , USA .
| | - Bhaskar Mondal
- Max Planck Institute for Chemical Energy Conversion , Stiftstraße 34-36 , Mülheim an der Ruhr , D-45470 , Germany
| | - Ida M DiMucci
- Department of Chemistry and Chemical Biology , Baker Laboratory , Cornell University , Ithaca , New York 14853 , USA
| | - Kyle M Lancaster
- Department of Chemistry and Chemical Biology , Baker Laboratory , Cornell University , Ithaca , New York 14853 , USA
| | - Jason Shearer
- Department of Chemistry , Trinity University , San Antonio , Texas 78212 , USA
| | - Eckhard Bill
- Max Planck Institute for Chemical Energy Conversion , Stiftstraße 34-36 , Mülheim an der Ruhr , D-45470 , Germany
| | - William W Brennessel
- Department of Chemistry , University of Rochester , Rochester , New York 14618 , USA
| | - Frank Neese
- Max Planck Institute for Coal Research , Kaiser-Wilhelm-Platz 1 , Mülheim an der Ruhr , D-45470 , Germany .
| | - Shengfa Ye
- Max Planck Institute for Coal Research , Kaiser-Wilhelm-Platz 1 , Mülheim an der Ruhr , D-45470 , Germany .
| | - Patrick L Holland
- Department of Chemistry , Yale University , New Haven , Connecticut 06520 , USA .
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26
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Wang P, Deng L. Recent Advances in Iron-Catalyzed C-H Bond AminationviaIron Imido Intermediate. CHINESE J CHEM 2018. [DOI: 10.1002/cjoc.201800427] [Citation(s) in RCA: 70] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Peng Wang
- State Key Laboratory of Organometallic Chemistry, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences; 345Lingling Road, Shanghai 200032 China
| | - Liang Deng
- State Key Laboratory of Organometallic Chemistry, Center for Excellence in Molecular Synthesis, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences; 345Lingling Road, Shanghai 200032 China
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27
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Mondal B, Neese F, Bill E, Ye S. Electronic Structure Contributions of Non-Heme Oxo-Iron(V) Complexes to the Reactivity. J Am Chem Soc 2018; 140:9531-9544. [PMID: 29984578 DOI: 10.1021/jacs.8b04275] [Citation(s) in RCA: 59] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Oxo-iron(V) species have been implicated in the catalytic cycle of the Rieske dioxygenase. Their synthetic analog, [FeV(O)(OC(O)CH3)(PyNMe3)]2+ (1, PyNMe3 = 3,6,9,15-tetraazabicyclo[9.3.1]pentadeca-1(15),11,13-triene-3,6,9-trimethyl), derived from the O-O bond cleavage of its acetylperoxo iron(III) precursor, has been shown experimentally to perform regio- and stereoselective C-H and C═C bond functionalization. However, its structure-activity relation is poorly understood. Herein we present a detailed electronic-structure and spectroscopic analysis of complex 1 along with well-characterized oxo-iron(V) complexes, [FeV(O)(TAML)]- (2, TAML = tetraamido macrocyclic ligand), [FeV(O)(TMC)(NC(O)CH3)]+ (4, TMC = 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane), and [FeV(O)(TMC)(NC(OH)CH3)]2+ (4-H+), using wave function-based multireference complete active-space self-consistent field calculations. Our results reveal that the x/ y anisotropy of the 57Fe A-matrix is not a reliable spectroscopic marker to identify oxo-iron(V) species and that the drastically different A x and A y values determined for complexes 1, 4, and 4-H+ have distinctive origins compared to complex 2, a genuine oxo-iron(V) species. Complex 1, in fact, has a dominant character of [FeIV(O···OC(O)CH3)2-•]2+, i.e., an SFe = 1 iron(IV) center antiferromagnetically coupled to an O-O σ* radical, where the O-O bond has not been completely broken. Complex 4 is best described as a triplet ferryl unit that strongly interacts with the trans acetylimidyl radical in an antiferromagnetic fashion, [FeIV(O)(•N═C(O-)CH3)]+. Complex 4-H+ features a similar electronic structure, [FeIV(O)(•N═C(OH)CH3)]2+. Owing to the remaining approximate half σ-bond in the O-O moiety, complex 1 can arrange two electron-accepting orbitals (α σ*O-O and β Fe-d xz) in such a way that both orbitals can simultaneously interact with the doubly occupied electron-donating orbitals (σC-H or πC-C). Hence, complex 1 can promote a concerted yet asynchronous two-electron oxidation of the C-H and C═C bonds, which nicely explains the stereospecificity observed for complex 1 and the related species.
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Affiliation(s)
- Bhaskar Mondal
- Max-Planck-Institut für Chemische Energiekonversion , D-45470 Mülheim an der Ruhr , Germany
| | - Frank Neese
- Max-Planck-Institut für Chemische Energiekonversion , D-45470 Mülheim an der Ruhr , Germany
| | - Eckhard Bill
- Max-Planck-Institut für Chemische Energiekonversion , D-45470 Mülheim an der Ruhr , Germany
| | - Shengfa Ye
- Max-Planck-Institut für Chemische Energiekonversion , D-45470 Mülheim an der Ruhr , Germany
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28
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Roy L. Theoretical Insights into the Nature of Oxidant and Mechanism in the Regioselective Syn
-dihydroxylation of an Alkene with a Rieske oxygenase inspired Iron Catalyst. ChemCatChem 2018. [DOI: 10.1002/cctc.201800799] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Lisa Roy
- Surface Engineering and Tribology Division; CSIR Central Mechanical Engineering Research Institute; Mahatma Gandhi Avenue Durgapur 713209 India
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29
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Pandey B, Jaccob M, Rajaraman G. Mechanistic insights into intramolecular ortho-amination/hydroxylation by nonheme Fe IV[double bond, length as m-dash]NTs/Fe IV[double bond, length as m-dash]O species: the σ vs. the π channels. Chem Commun (Camb) 2018; 53:3193-3196. [PMID: 28220156 DOI: 10.1039/c6cc08761b] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Comparative oxidative abilities of nonheme FeIV[double bond, length as m-dash]NTs and FeIV[double bond, length as m-dash]O species using DFT has been explored. Our calculations reveal that the FeIV[double bond, length as m-dash]NTs is found to be a stronger oxidant in two electron transfer reactions and react exclusively via π channels while the FeIV[double bond, length as m-dash]O species is found to be a stronger oxidant when the σ-pathway is activated such as in HAT reactions.
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Affiliation(s)
- Bhawana Pandey
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra 400076, India.
| | - Madhavan Jaccob
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra 400076, India. and Department of Chemistry, Loyola College, Chennai 600 034, Tamil Nadu, India
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra 400076, India.
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30
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Andris E, Navrátil R, Jašík J, Sabenya G, Costas M, Srnec M, Roithová J. Detection of Indistinct Fe−N Stretching Bands in Iron(V) Nitrides by Photodissociation Spectroscopy. Chemistry 2018; 24:5078-5081. [DOI: 10.1002/chem.201705307] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2017] [Indexed: 12/23/2022]
Affiliation(s)
- Erik Andris
- Department of Organic Chemistry, Faculty of Science; Charles University; Hlavova 2030/8 128 43 Prague 2 Czech Republic
| | - Rafael Navrátil
- Department of Organic Chemistry, Faculty of Science; Charles University; Hlavova 2030/8 128 43 Prague 2 Czech Republic
| | - Juraj Jašík
- Department of Organic Chemistry, Faculty of Science; Charles University; Hlavova 2030/8 128 43 Prague 2 Czech Republic
| | - Gerard Sabenya
- Departament de Quimica and Institute of Computational Chemistry and Catalysis (IQCC); University of Girona, Campus Montilivi; Girona 17071 Spain
| | - Miquel Costas
- Departament de Quimica and Institute of Computational Chemistry and Catalysis (IQCC); University of Girona, Campus Montilivi; Girona 17071 Spain
| | - Martin Srnec
- J. Heyrovsky Institute of Physical Chemistry of the CAS, v. v. i.; Dolejškova 2155/3 182 23 Prague 8 Czech Republic
| | - Jana Roithová
- Department of Organic Chemistry, Faculty of Science; Charles University; Hlavova 2030/8 128 43 Prague 2 Czech Republic
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31
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Kupper C, Mondal B, Serrano-Plana J, Klawitter I, Neese F, Costas M, Ye S, Meyer F. Nonclassical Single-State Reactivity of an Oxo-Iron(IV) Complex Confined to Triplet Pathways. J Am Chem Soc 2017; 139:8939-8949. [PMID: 28557448 DOI: 10.1021/jacs.7b03255] [Citation(s) in RCA: 78] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
C-H bond activation mediated by oxo-iron (IV) species represents the key step of many heme and nonheme O2-activating enzymes. Of crucial interest is the effect of spin state of the FeIV(O) unit. Here we report the C-H activation kinetics and corresponding theoretical investigations of an exclusive tetracarbene ligated oxo-iron(IV) complex, [LNHCFeIV(O)(MeCN)]2+ (1). Kinetic traces using substrates with bond dissociation energies (BDEs) up to 80 kcal mol-1 show pseudo-first-order behavior and large but temperature-dependent kinetic isotope effects (KIE 32 at -40 °C). When compared with a topologically related oxo-iron(IV) complex bearing an equatorial N-donor ligand, [LTMCFeIV(O) (MeCN)]2+ (A), the tetracarbene complex 1 is significantly more reactive with second order rate constants k'2 that are 2-3 orders of magnitude higher. UV-vis experiments in tandem with cryospray mass spectrometry evidence that the reaction occurs via formation of a hydroxo-iron(III) complex (4) after the initial H atom transfer (HAT). An extensive computational study using a wave function based multireference approach, viz. complete active space self-consistent field (CASSCF) followed by N-electron valence perturbation theory up to second order (NEVPT2), provided insight into the HAT trajectories of 1 and A. Calculated free energy barriers for 1 reasonably agree with experimental values. Because the strongly donating equatorial tetracarbene pushes the Fe-dx2-y2 orbital above dz2, 1 features a dramatically large quintet-triplet gap of ∼18 kcal/mol compared to ∼2-3 kcal/mol computed for A. Consequently, the HAT process performed by 1 occurs on the triplet surface only, in contrast to complex A reported to feature two-state-reactivity with contributions from both triplet and quintet states. Despite this, the reactive FeIV(O) units in 1 and A undergo the same electronic-structure changes during HAT. Thus, the unique complex 1 represents a pure "triplet-only" ferryl model.
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Affiliation(s)
- Claudia Kupper
- Universität Göttingen , Institut für Anorganische Chemie, Tammannstrasse 4, 37077 Göttingen, Germany
| | - Bhaskar Mondal
- Max-Planck Institut für Chemische Energiekonversion , Stiftstrasse 34-36, 45470 Mülheim an der Ruhr, Germany
| | - Joan Serrano-Plana
- Institut de Química Computacional i Catàlisi (IQCC), Departament de Quimica, Universitat de Girona , Campus Montilivi, E17071 Girona, Catalonia, Spain
| | - Iris Klawitter
- Universität Göttingen , Institut für Anorganische Chemie, Tammannstrasse 4, 37077 Göttingen, Germany
| | - Frank Neese
- Max-Planck Institut für Chemische Energiekonversion , Stiftstrasse 34-36, 45470 Mülheim an der Ruhr, Germany
| | - Miquel Costas
- Institut de Química Computacional i Catàlisi (IQCC), Departament de Quimica, Universitat de Girona , Campus Montilivi, E17071 Girona, Catalonia, Spain
| | - Shengfa Ye
- Max-Planck Institut für Chemische Energiekonversion , Stiftstrasse 34-36, 45470 Mülheim an der Ruhr, Germany
| | - Franc Meyer
- Universität Göttingen , Institut für Anorganische Chemie, Tammannstrasse 4, 37077 Göttingen, Germany
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32
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Ye S, Kupper C, Meyer S, Andris E, Navrátil R, Krahe O, Mondal B, Atanasov M, Bill E, Roithová J, Meyer F, Neese F. Magnetic Circular Dichroism Evidence for an Unusual Electronic Structure of a Tetracarbene-Oxoiron(IV) Complex. J Am Chem Soc 2016; 138:14312-14325. [PMID: 27682505 DOI: 10.1021/jacs.6b07708] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In biology, high valent oxo-iron(IV) species have been shown to be pivotal intermediates for functionalization of C-H bonds in the catalytic cycles of a range of O2-activating iron enzymes. This work details an electronic-structure investigation of [FeIV(O)(LNHC)(NCMe)]2+ (LNHC = 3,9,14,20-tetraaza-1,6,12,17-tetraazoniapenta-cyclohexacosane-1(23),4,6(26),10,12(25),15,17(24),21-octaene, complex 1) using helium tagging infrared photodissociation (IRPD), absorption, and magnetic circular dichroism (MCD) spectroscopy, coupled with DFT and highly correlated wave function based multireference calculations. The IRPD spectrum of complex 1 reveals the Fe-O stretching vibration at 832 ± 3 cm-1. By analyzing the Franck-Condon progression, we can determine the same vibration occurring at 616 ± 10 cm-1 in the E(dxy → dxz,yz) excited state. Both values are similar to those measured for [FeIV(O)(TMC)(NCMe)]2+ (TMC = 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane). The low-temperature MCD spectra of complex 1 exhibit three pseudo A-term signals around 12 500, 17 000, and 24 300 cm-1. We can unequivocally assign them to the ligand field transitions of dxy → dxz,yz, dxz,yz → dz2, and dxz,yz → dx2-y2, respectively, through direct calculations of MCD spectra and independent determination of the MCD C-term signs from the corresponding electron donating and accepting orbitals. In comparison with the corresponding transitions observed for [FeIV(O) (SR-TPA)(NCMe)]2+ (SR-TPA = tris(3,5-dimethyl-4-methoxypyridyl-2-methy)amine), the excitations within the (FeO)2+ core of complex 1 have similar transition energies, whereas the excitation energy for dxz,yz → dx2-y2 is significantly higher (∼12 000 cm-1 for [FeIV(O)(SR-TPA)(NCMe)]2+). Our results thus substantiate that the tetracarbene ligand (LNHC) of complex 1 does not significantly affect the bonding in the (FeO)2+ unit but strongly destabilizes the dx2-y2 orbital to eventually lift it above dz2. As a consequence, this unusual electron configuration leads to an unprecedentedly larger quintet-triplet energy separation for complex 1, which largely rules out the possibility that the H atom transfer reaction may take place on the quintet surface and hence quenches two-state reactivity. The resulting mechanistic implications are discussed.
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Affiliation(s)
- Shengfa Ye
- Max-Planck Institut für Chemische Energiekonversion, Stiftstr. 34-36, D-45470 Mülheim an der Ruhr, Germany
| | - Claudia Kupper
- Institut für Anorganische Chemie, Georg-August-Universität Göttingen , Tammannstr. 4, D-37077 Göttingen, Germany
| | - Steffen Meyer
- Institut für Anorganische Chemie, Georg-August-Universität Göttingen , Tammannstr. 4, D-37077 Göttingen, Germany
| | - Erik Andris
- Department of Organic Chemistry, Faculty of Science, Charles University in Prague , Hlavova 8, 128 43 Praha 2, Czech Republic
| | - Rafael Navrátil
- Department of Organic Chemistry, Faculty of Science, Charles University in Prague , Hlavova 8, 128 43 Praha 2, Czech Republic
| | - Oliver Krahe
- Max-Planck Institut für Chemische Energiekonversion, Stiftstr. 34-36, D-45470 Mülheim an der Ruhr, Germany
| | - Bhaskar Mondal
- Max-Planck Institut für Chemische Energiekonversion, Stiftstr. 34-36, D-45470 Mülheim an der Ruhr, Germany
| | - Mihail Atanasov
- Max-Planck Institut für Chemische Energiekonversion, Stiftstr. 34-36, D-45470 Mülheim an der Ruhr, Germany.,Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences , 1113 Sofia, Bulgaria
| | - Eckhard Bill
- Max-Planck Institut für Chemische Energiekonversion, Stiftstr. 34-36, D-45470 Mülheim an der Ruhr, Germany
| | - Jana Roithová
- Department of Organic Chemistry, Faculty of Science, Charles University in Prague , Hlavova 8, 128 43 Praha 2, Czech Republic
| | - Franc Meyer
- Institut für Anorganische Chemie, Georg-August-Universität Göttingen , Tammannstr. 4, D-37077 Göttingen, Germany
| | - Frank Neese
- Max-Planck Institut für Chemische Energiekonversion, Stiftstr. 34-36, D-45470 Mülheim an der Ruhr, Germany
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