1
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Wilson DWN, Thompson BC, Collauto A, Hooper RX, Knapp CE, Roessler MM, Musgrave RA. Mixed Valence {Ni 2+Ni 1+} Clusters as Models of Acetyl Coenzyme A Synthase Intermediates. J Am Chem Soc 2024; 146:21034-21043. [PMID: 39023163 PMCID: PMC11295191 DOI: 10.1021/jacs.4c06241] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2024] [Revised: 06/12/2024] [Accepted: 06/13/2024] [Indexed: 07/20/2024]
Abstract
Acetyl coenzyme A synthase (ACS) catalyzes the formation and deconstruction of the key biological metabolite, acetyl coenzyme A (acetyl-CoA). The active site of ACS features a {NiNi} cluster bridged to a [Fe4S4]n+ cubane known as the A-cluster. The mechanism by which the A-cluster functions is debated, with few model complexes able to replicate the oxidation states, coordination features, or reactivity proposed in the catalytic cycle. In this work, we isolate the first bimetallic models of two hypothesized intermediates on the paramagnetic pathway of the ACS function. The heteroligated {Ni2+Ni1+} cluster, [K(12-crown-4)2][1], effectively replicates the coordination number and oxidation state of the proposed "Ared" state of the A-cluster. Addition of carbon monoxide to [1]- allows for isolation of a dinuclear {Ni2+Ni1+(CO)} complex, [K(12-crown-2)n][2] (n = 1-2), which bears similarity to the "ANiFeC" enzyme intermediate. Structural and electronic properties of each cluster are elucidated by X-ray diffraction, nuclear magnetic resonance, cyclic voltammetry, and UV/vis and electron paramagnetic resonance spectroscopies, which are supplemented by density functional theory (DFT) calculations. Calculations indicate that the pseudo-T-shaped geometry of the three-coordinate nickel in [1]- is more stable than the Y-conformation by 22 kcal mol-1, and that binding of CO to Ni1+ is barrierless and exergonic by 6 kcal mol-1. UV/vis absorption spectroscopy on [2]- in conjunction with time-dependent DFT calculations indicates that the square-planar nickel site is involved in electron transfer to the CO π*-orbital. Further, we demonstrate that [2]- promotes thioester synthesis in a reaction analogous to the production of acetyl coenzyme A by ACS.
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Affiliation(s)
- Daniel W. N. Wilson
- Department
of Chemistry, King’s College London, 7 Trinity Street, London SE1 1DB, U.K.
- Department
of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K.
| | - Benedict C. Thompson
- Department
of Chemistry, King’s College London, 7 Trinity Street, London SE1 1DB, U.K.
| | - Alberto Collauto
- Department
of Chemistry and Centre for Pulse EPR Spectroscopy, Imperial College London, 82 Wood Lane, London W12
0BZ, U.K.
| | - Reagan X. Hooper
- Stanford
PULSE Institute, SLAC National Accelerator
Laboratory, Menlo Park, California 94025, United States
| | - Caroline E. Knapp
- Department
of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, U.K.
| | - Maxie M. Roessler
- Department
of Chemistry and Centre for Pulse EPR Spectroscopy, Imperial College London, 82 Wood Lane, London W12
0BZ, U.K.
| | - Rebecca A. Musgrave
- Department
of Chemistry, King’s College London, 7 Trinity Street, London SE1 1DB, U.K.
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2
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Brown AC, Suess DLM. An Iron-Sulfur Cluster with a Highly Pyramidalized Three-Coordinate Iron Center and a Negligible Affinity for Dinitrogen. J Am Chem Soc 2023; 145:20088-20096. [PMID: 37656961 PMCID: PMC10824254 DOI: 10.1021/jacs.3c07677] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/03/2023]
Abstract
Attempts to generate open coordination sites for N2 binding at synthetic Fe-S clusters often instead result in cluster oligomerization. Recently, it was shown for Mo-Fe-S clusters that such oligomerization reactions can be prevented through the use of sterically protective supporting ligands, thereby enabling N2 complex formation. Here, this strategy is extended to Fe-only Fe-S clusters. One-electron reduction of (IMes)3Fe4S4Cl (IMes = 1,3-dimesitylimidazol-2-ylidene) forms the transiently stable edge-bridged double cubane (IMes)6Fe8S8, which loses two IMes ligands to form the face-bridged double-cubane, (IMes)4Fe8S8. The finding that the three supporting IMes ligands do not confer sufficient protection to curtail cluster oligomerization prompted the design of a new N-heterocyclic carbene, SIArMe,iPr (1,3-bis(3,5-diisopropyl-2,6-dimethylphenyl)-2-imidazolidinylidene; abbreviated as SIAr), that features bulky groups strategically placed in remote positions. When the reduction of (SIAr)3Fe4S4Cl or [(SIAr)3Fe4S4(THF)]+ is conducted in the presence of SIAr, the formation of (SIAr)4Fe8S8 is indeed suppressed, permitting characterization of the reduced [Fe4S4]0 product. Surprisingly, rather than being an N2 complex, the product is simply (SIAr)3Fe4S4: a cluster with a three-coordinate Fe site that adopts an unusually pyramidalized geometry. Although (SIAr)3Fe4S4 does not coordinate N2 to any appreciable extent under the surveyed conditions, it does bind CO to form (SIAr)3Fe4S4(CO). This finding demonstates that the binding pocket at the unique Fe is not too small for N2; instead, the exceptionally weak affinity for N2 can be attributed to weak Fe-N2 bonding. The differences in the N2 coordination chemistry between sterically protected Mo-Fe-S clusters and Fe-only Fe-S clusters are discussed.
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Affiliation(s)
- Alexandra C Brown
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Daniel L M Suess
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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3
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Bostelaar TM, Brown AC, Sridharan A, Suess DLM. A general method for metallocluster site-differentiation. NATURE SYNTHESIS 2023; 2:740-748. [PMID: 39055685 PMCID: PMC11271975 DOI: 10.1038/s44160-023-00286-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2022] [Accepted: 03/02/2023] [Indexed: 07/27/2024]
Abstract
The deployment of metalloclusters in applications such as catalysis and materials synthesis requires robust methods for site-differentiation: the conversion of clusters with symmetric ligand spheres to those with unsymmetrical ligand spheres. However, imparting precise patterns of site-differentiation is challenging because, compared with mononuclear complexes, the ligands bound to clusters exert limited spatial and electronic influence on one another. Here, we report a method that employs sterically encumbering ligands to bind to only a subset of a cluster's coordination sites. Specifically, we show that homoleptic, phosphine-ligated Fe-S clusters undergo ligand substitution with N-heterocyclic carbenes (NHCs) to give heteroleptic clusters in which the resultant clusters' site-differentiation patterns are encoded by the steric profile of the incoming NHC. This method affords access to every site-differentiation pattern for cuboidal [Fe4S4] clusters and can be extended to other cluster types, particularly in the stereoselective synthesis of site-differentiated Chevrel-type [Fe6S8] clusters.
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Affiliation(s)
- Trever M Bostelaar
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Alexandra C Brown
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Arun Sridharan
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Daniel L M Suess
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, USA
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4
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Skeel BA, Suess DLM. Exploiting Molecular Symmetry to Quantitatively Map the Excited-State Landscape of Iron-Sulfur Clusters. J Am Chem Soc 2023; 145:10376-10395. [PMID: 37125463 DOI: 10.1021/jacs.3c02412] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
Cuboidal [Fe4S4] clusters are ubiquitous cofactors in biological redox chemistry. In the [Fe4S4]1+ state, pairwise spin coupling gives rise to six arrangements of the Fe valences ("valence isomers") among the four Fe centers. Because of the magnetic complexity of these systems, it has been challenging to understand how a protein's active site dictates both the arrangement of the valences in the ground state as well as the population of excited-state valence isomers. Here, we show that the ground-state valence isomer landscape can be simplified from a six-level system in an asymmetric protein environment to a two-level system by studying the problem in synthetic [Fe4S4]1+ clusters with solution C3v symmetry. This simplification allows for the energy differences between valence isomers to be quantified (in some cases with a resolution of <0.1 kcal/mol) by simultaneously fitting the VT NMR and solution magnetic moment data. Using this fitting protocol, we map the excited-state landscape for a range of clusters of the form [(SIMes)3Fe4S4-X/L]n, (SIMes = 1,3-dimesityl-imidazol-4,5-dihydro-2-ylidene; n = 0 for anionic, X-type ligands and n = +1 for neutral, L-type ligands) and find that a single ligand substitution can alter the relative ground-state energies of valence isomers by at least 103 cm-1. On this basis, we suggest that one result of "non-canonical" amino acid ligation in Fe-S proteins is the redistribution of the valence electrons in the manifold of thermally populated excited states.
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Affiliation(s)
- Brighton A Skeel
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Daniel L M Suess
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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5
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Brown AC, Suess DLM. Valence Localization in Alkyne and Alkene Adducts of Synthetic [Fe 4S 4] + Clusters. Inorg Chem 2023; 62:1911-1918. [PMID: 35704768 PMCID: PMC9751231 DOI: 10.1021/acs.inorgchem.2c01353] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Reported herein are alkyne and alkene adducts of synthetic [Fe4S4]+ clusters that model intermediates and inhibitor-bound states in enzymes involved in isoprenoid biosynthesis. Treatment of the N-heterocyclic carbene-ligated cluster [(IMes)3Fe4S4(OEt2)][BArF4] (IMes = 1,3-dimesitylimidazol-2-ylidene; [BArF4]- = tetrakis(3,5-bis(trifluoromethyl)phenyl)borate) with phenylacetylene (PhCCH) or cis-cyclooctene (COE) results in displacement of the Et2O ligand to yield the corresponding π complexes, [(IMes)3Fe4S4(PhCCH)][BArF4] and [(IMes)3Fe4S4(COE)][BArF4]. EPR spectroscopic analysis demonstrates that both clusters are doublets with giso > 2 and thus are spectroscopically faithful models of the analogous species characterized in the isoprenoid biosynthetic enzymes IspG and IspH. Structural and Mössbauer spectroscopic analysis reveals that both complexes are best described as [Fe4S4]+ clusters in which the unique Fe site engages in modest back-bonding to the π-acidic ligand. Paramagnetic NMR studies show that, even at room temperature, the alkyne/alkene-bound Fe centers harbor minority spin and therefore adopt an Fe2+ valence. We propose that such valence localization could likewise occur in Fe-S enzymes that interact with π-acidic molecules.
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6
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Brown AC, Suess DLM. An Open-Cuboidal [Fe 3S 4] Cluster Characterized in Both Biologically Relevant Redox States. J Am Chem Soc 2023; 145:2075-2080. [PMID: 36688844 DOI: 10.1021/jacs.2c13126] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Synthetic analogues of the three common types of Fe-S clusters found in biology─diamond-core [Fe2S2] clusters, open-cuboidal [Fe3S4] clusters, and cuboidal [Fe4S4] clusters─have been reported in each biologically relevant redox state with one exception: the open-cuboidal [Fe3S4]+ cluster. Here, we describe the synthesis and characterization of an open-cuboidal [Fe3S4] cluster in both biologically relevant redox states: [Fe3S4]+ and [Fe3S4]0. Like their biological counterparts, the oxidized cluster has a spin-canted, S = 1/2 ground state, and the reduced cluster has an S = 2 ground state. Structural analysis reveals that the [Fe3S4] core undergoes substantial contraction upon oxidation, in contrast to the minimal structural changes observed for the only [Fe3S4] protein for which high-resolution structures are available in both redox states (Azotobacter vinelandii ferredoxin I; Av FdI). This difference between the synthetic models and Av FdI is discussed in the context of electron transfer by [Fe3S4] proteins.
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Affiliation(s)
- Alexandra C Brown
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Daniel L M Suess
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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7
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Kim Y, Sridharan A, Suess DLM. The Elusive Mononitrosylated [Fe 4 S 4 ] Cluster in Three Redox States. Angew Chem Int Ed Engl 2022; 61:e202213032. [PMID: 36194444 PMCID: PMC9669169 DOI: 10.1002/anie.202213032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2022] [Indexed: 11/06/2022]
Abstract
Iron-sulfur clusters are well-established targets in biological nitric oxide (NO) chemistry, but the key intermediate in these processes-a mononitrosylated [Fe4 S4 ] cluster-has not been fully characterized in a protein or a synthetic model thereof. Here, we report the synthesis of a three-member redox series of isostructural mononitrosylated [Fe4 S4 ] clusters. Mononitrosylation was achieved by binding NO to a 3 : 1 site-differentiated [Fe4 S4 ]+ cluster; subsequent oxidation and reduction afforded the other members of the series. All three clusters feature a local high-spin Fe3+ center antiferromagnetically coupled to 3 [NO]- . The observation of an anionic NO ligand suggests that NO binding is accompanied by formal electron transfer from the cluster to NO. Preliminary reactivity studies with the monocationic cluster demonstrate that exposure to excess NO degrades the cluster, supporting the intermediacy of mononitrosylated intermediates in NO sensing/signaling.
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Affiliation(s)
- Youngsuk Kim
- Department of ChemistryMassachusetts Institute of Technology77 Massachusetts AveCambridgeMA 02139USA
- Department of ChemistryPusan National UniversityBusan46241Republic of Korea
| | - Arun Sridharan
- Department of ChemistryMassachusetts Institute of Technology77 Massachusetts AveCambridgeMA 02139USA
| | - Daniel L. M. Suess
- Department of ChemistryMassachusetts Institute of Technology77 Massachusetts AveCambridgeMA 02139USA
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8
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Santos-Carballal D, de Leeuw NH. Catalytic formation of oxalic acid on the partially oxidised greigite Fe 3S 4(001) surface. Phys Chem Chem Phys 2022; 24:20104-20124. [PMID: 35983830 DOI: 10.1039/d2cp00333c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Greigite (Fe3S4), with its ferredoxin-like 4Fe-4S redox centres, is a naturally occurring mineral capable of acting as a catalyst in the conversion of carbon dioxide (CO2) into low molecular-weight organic acids (LMWOAs), which are of paramount significance in several soil and plant processes as well as in the chemical industry. In this paper, we report the reaction between CO2 and water (H2O) to form oxalic acid (H2C2O4) on the partially oxidised greigite Fe3S4(001) surface by means of spin-polarised density functional theory calculations with on-site Coulomb corrections and long-range dispersion interactions (DFT+U-D2). We have calculated the bulk phase of Fe3S4 and the two reconstructed Tasker type 3 terminations of its (001) surface, whose properties are in good agreement with available experimental data. We have obtained the relevant phase diagram, showing that the Fe3S4(001) surface becomes 62.5% partially oxidised, by replacing S by O atoms, in the presence of water at the typical conditions of calcination [Mitchell et al. Faraday Discuss. 2021, 230, 30-51]. The adsorption and co-adsorption of the reactants on the partially oxidised Fe3S4(001) surface are exothermic processes. We have considered three mechanistic pathways to explain the formation of H2C2O4, showing that the coupling of the C-C bond and second protonation are the elementary steps with the largest energy penalty. Our calculations suggest that the partially oxidised Fe3S4(001) surface is a mineral phase that can catalyse the formation of H2C2O4 under favourable conditions, which has important implications for natural ecosystems and is a process that can be harnessed for the industrial manufacture of this organic acid.
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Affiliation(s)
| | - Nora H de Leeuw
- School of Chemistry, University of Leeds, Leeds LS2 9JT, UK. .,Department of Earth Sciences, Utrecht University, Princetonplein 8A, 3584 CD Utrecht, The Netherlands.
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9
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Brown AC, Thompson NB, Suess DLM. Evidence for Low-Valent Electronic Configurations in Iron-Sulfur Clusters. J Am Chem Soc 2022; 144:9066-9073. [PMID: 35575703 DOI: 10.1021/jacs.2c01872] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Although biological iron-sulfur (Fe-S) clusters perform some of the most difficult redox reactions in nature, they are thought to be composed exclusively of Fe2+ and Fe3+ ions, as well as mixed-valent pairs with average oxidation states of Fe2.5+. We herein show that Fe-S clusters formally composed of these valences can access a wider range of electronic configurations─in particular, those featuring low-valent Fe1+ centers. We demonstrate that CO binding to a synthetic [Fe4S4]0 cluster supported by N-heterocyclic carbene ligands induces the generation of Fe1+ centers via intracluster electron transfer, wherein a neighboring pair of Fe2+ sites reduces the CO-bound site to a low-valent Fe1+ state. Similarly, CO binding to an [Fe4S4]+ cluster induces electron delocalization with a neighboring Fe site to form a mixed-valent Fe1.5+Fe2.5+ pair in which the CO-bound site adopts partial low-valent character. These low-valent configurations engender remarkable C-O bond activation without having to traverse highly negative and physiologically inaccessible [Fe4S4]0/[Fe4S4]- redox couples.
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Affiliation(s)
- Alexandra C Brown
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Niklas B Thompson
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Daniel L M Suess
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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10
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Boncella AE, Sabo ET, Santore RM, Carter J, Whalen J, Hudspeth JD, Morrison CN. The expanding utility of iron-sulfur clusters: Their functional roles in biology, synthetic small molecules, maquettes and artificial proteins, biomimetic materials, and therapeutic strategies. Coord Chem Rev 2022. [DOI: 10.1016/j.ccr.2021.214229] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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11
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Jobelius H, Bianchino GI, Borel F, Chaignon P, Seemann M. The Reductive Dehydroxylation Catalyzed by IspH, a Source of Inspiration for the Development of Novel Anti-Infectives. MOLECULES (BASEL, SWITZERLAND) 2022; 27:molecules27030708. [PMID: 35163971 PMCID: PMC8837944 DOI: 10.3390/molecules27030708] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/05/2021] [Revised: 01/11/2022] [Accepted: 01/18/2022] [Indexed: 11/16/2022]
Abstract
The non-mevalonate or also called MEP pathway is an essential route for the biosynthesis of isoprenoid precursors in most bacteria and in microorganisms belonging to the Apicomplexa phylum, such as the parasite responsible for malaria. The absence of this pathway in mammalians makes it an interesting target for the discovery of novel anti-infectives. As last enzyme of this pathway, IspH is an oxygen sensitive [4Fe-4S] metalloenzyme that catalyzes 2H+/2e− reductions and a water elimination by involving non-conventional bioinorganic and bioorganometallic intermediates. After a detailed description of the discovery of the [4Fe-4S] cluster of IspH, this review focuses on the IspH mechanism discussing the results that have been obtained in the last decades using an approach combining chemistry, enzymology, crystallography, spectroscopies, and docking calculations. Considering the interesting druggability of this enzyme, a section about the inhibitors of IspH discovered up to now is reported as well. The presented results constitute a useful and rational help to inaugurate the design and development of new potential chemotherapeutics against pathogenic organisms.
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Affiliation(s)
- Hannah Jobelius
- Equipe Chimie Biologique et Applications Thérapeutiques, Institut de Chimie de Strasbourg UMR 7177, Université de Strasbourg/CNRS, 4, rue Blaise Pascal, 67070 Strasbourg, France; (H.J.); (G.I.B.); (P.C.)
| | - Gabriella Ines Bianchino
- Equipe Chimie Biologique et Applications Thérapeutiques, Institut de Chimie de Strasbourg UMR 7177, Université de Strasbourg/CNRS, 4, rue Blaise Pascal, 67070 Strasbourg, France; (H.J.); (G.I.B.); (P.C.)
| | - Franck Borel
- Institut de Biologie Structurale, Université Grenoble Alpes/CEA/CNRS, 38000 Grenoble, France;
| | - Philippe Chaignon
- Equipe Chimie Biologique et Applications Thérapeutiques, Institut de Chimie de Strasbourg UMR 7177, Université de Strasbourg/CNRS, 4, rue Blaise Pascal, 67070 Strasbourg, France; (H.J.); (G.I.B.); (P.C.)
| | - Myriam Seemann
- Equipe Chimie Biologique et Applications Thérapeutiques, Institut de Chimie de Strasbourg UMR 7177, Université de Strasbourg/CNRS, 4, rue Blaise Pascal, 67070 Strasbourg, France; (H.J.); (G.I.B.); (P.C.)
- Correspondence:
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12
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Reed DA, Hochuli TJ, Gadjieva NA, He S, Wiscons RA, Bartholomew AK, Champsaur AM, Steigerwald ML, Roy X, Nuckolls C. Controlling Ligand Coordination Spheres and Cluster Fusion in Superatoms. J Am Chem Soc 2021; 144:306-313. [PMID: 34937334 DOI: 10.1021/jacs.1c09901] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
We show that reaction pathways from a single superatom motif can be controlled through subtle electronic modification of the outer ligand spheres. Chevrel-type [Co6Se8L6] (L = PR3, CO) superatoms are used to form carbene-terminated clusters, the reactivity of which can be influenced through the electronic effects of the surrounding ligands. This carbene provides new routes for ligand substitution chemistry, which is used to selectively install cyanide or pyridine ligands which were previously inaccessible in these cobalt-based clusters. The surrounding ligands also impact the ability of this carbene to create larger fused clusters of the type [Co12Se16L10], providing underlying information for cluster fusion mechanisms. We use this information to develop methods of creating dimeric clusters with functionalized surface ligands with site specificity, putting new ligands in specific positions on this anisotropic core. Finally, adjusting the carbene intermediates can also be used to perturb the geometry of the [Co6Se8] core itself, as we demonstrate with a multicarbene adduct that displays a substantially anisotropic core. These additional levels of synthetic control could prove instrumental for using superatomic clusters for many applications including catalysis, electronic devices, and creating novel extended structures.
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Affiliation(s)
- Douglas A Reed
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Taylor J Hochuli
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Natalia A Gadjieva
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Shoushou He
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Ren A Wiscons
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | | | - Anouck M Champsaur
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Michael L Steigerwald
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Xavier Roy
- Department of Chemistry, Columbia University, New York, New York 10027, United States
| | - Colin Nuckolls
- Department of Chemistry, Columbia University, New York, New York 10027, United States
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13
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Wang CH, DeBeer S. Structure, reactivity, and spectroscopy of nitrogenase-related synthetic and biological clusters. Chem Soc Rev 2021; 50:8743-8761. [PMID: 34159992 DOI: 10.1039/d1cs00381j] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The reduction of dinitrogen (N2) is essential for its incorporation into nucleic acids and amino acids, which are vital to life on earth. Nitrogenases convert atmospheric dinitrogen to two ammonia molecules (NH3) under ambient conditions. The catalytic active sites of these enzymes (known as FeM-cofactor clusters, where M = Mo, V, Fe) are the sites of N2 binding and activation and have been a source of great interest for chemists for decades. In this review, recent studies on nitrogenase-related synthetic molecular complexes and biological clusters are discussed, with a focus on their reactivity and spectroscopic characterization. The molecular models that are discussed span from simple mononuclear iron complexes to multinuclear iron complexes and heterometallic iron complexes. In addition, recent work on the extracted biological cofactors is discussed. An emphasis is placed on how these studies have contributed towards our understanding of the electronic structure and mechanism of nitrogenases.
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Affiliation(s)
- Chen-Hao Wang
- Max Planck Institute for Chemical Energy Conversion, Stiftstr. 34-36, 45470 Mülheim an der Ruhr, Germany.
| | - Serena DeBeer
- Max Planck Institute for Chemical Energy Conversion, Stiftstr. 34-36, 45470 Mülheim an der Ruhr, Germany.
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14
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McSkimming A, Suess DLM. Dinitrogen binding and activation at a molybdenum-iron-sulfur cluster. Nat Chem 2021; 13:666-670. [PMID: 34045715 DOI: 10.1038/s41557-021-00701-6] [Citation(s) in RCA: 43] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2020] [Accepted: 04/09/2021] [Indexed: 02/07/2023]
Abstract
The Fe-S clusters of nitrogenases carry out the life-sustaining conversion of N2 to NH3. Although progress continues to be made in modelling the structural features of nitrogenase cofactors, no synthetic Fe-S cluster has been shown to form a well-defined coordination complex with N2. Here we report that embedding an [MoFe3S4] cluster in a protective ligand environment enables N2 binding at Fe. The bridging [MoFe3S4]2(μ-η1:η1-N2) complex thus prepared features a substantially weakened N-N bond despite the relatively high formal oxidation states of the metal centres. Substitution of one of the [MoFe3S4] cubanes with an electropositive Ti metalloradical induces additional charge transfer to the N2 ligand with generation of Fe-N multiple-bond character. Structural and spectroscopic analyses demonstrate that N2 activation is accompanied by shortened Fe-S distances and charge transfer from each Fe site, including those not directly bound to N2. These findings indicate that covalent interactions within the cluster play a critical role in N2 binding and activation.
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Affiliation(s)
- Alex McSkimming
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, USA.,Department of Chemistry, Tulane University, New Orleans, LA, USA
| | - Daniel L M Suess
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, USA.
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Sridharan A, Brown AC, Suess DLM. A Terminal Imido Complex of an Iron-Sulfur Cluster. Angew Chem Int Ed Engl 2021; 60:12802-12806. [PMID: 33772994 DOI: 10.1002/anie.202102603] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2021] [Indexed: 11/10/2022]
Abstract
We report the synthesis and characterization of the first terminal imido complex of an Fe-S cluster, (IMes)3 Fe4 S4 =NDipp (2; IMes=1,3-dimesitylimidazol-2-ylidene, Dipp=2,6-diisopropylphenyl), which is generated by oxidative group transfer from DippN3 to the all-ferrous cluster (IMes)3 Fe4 S4 (PPh3 ). This two-electron process is achieved by formal one-electron oxidation of the imido-bound Fe site and one-electron oxidation of two IMes-bound Fe sites. Structural, spectroscopic, and computational studies establish that the Fe-imido site is best described as a high-spin Fe3+ center, which is manifested in its long Fe-N(imido) distance of 1.763(2) Å. Cluster 2 abstracts hydrogen atoms from 1,4-cyclohexadiene to yield the corresponding anilido complex, demonstrating competency for C-H activation.
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Affiliation(s)
- Arun Sridharan
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA, 02139, USA
| | - Alexandra C Brown
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA, 02139, USA
| | - Daniel L M Suess
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA, 02139, USA
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Sridharan A, Brown AC, Suess DLM. A Terminal Imido Complex of an Iron–Sulfur Cluster. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202102603] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Arun Sridharan
- Department of Chemistry Massachusetts Institute of Technology 77 Massachusetts Ave Cambridge MA 02139 USA
| | - Alexandra C. Brown
- Department of Chemistry Massachusetts Institute of Technology 77 Massachusetts Ave Cambridge MA 02139 USA
| | - Daniel L. M. Suess
- Department of Chemistry Massachusetts Institute of Technology 77 Massachusetts Ave Cambridge MA 02139 USA
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Speelman AL, Skubi KL, Mercado BQ, Holland PL. Synthesis and Reactivity of Iron Complexes with a Biomimetic SCS Pincer Ligand. Inorg Chem 2021; 60:1965-1974. [PMID: 33443404 DOI: 10.1021/acs.inorgchem.0c03427] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Recent experimental evidence suggests that the FeMoco of nitrogenase undergoes structural rearrangement during N2 reduction, which may result in the generation of coordinatively unsaturated iron sites with two sulfur donors and a carbon donor. In an effort to synthesize and study small-molecule model complexes with a one-carbon/two-sulfur coordination environment, we have designed two new SCS pincer ligands containing a central NHC donor accompanied by thioether- or thiolate-functionalized aryl groups. Metalation of the thioether ligand with Fe(OTf)2 gives 6-coordinate complexes in which the SCS ligand binds meridionally. In contrast, metalation of the thiolate ligand with Fe(HMDS)2 gives a four-coordinate pseudotetrahedral amide complex in which the ligand binds facially, illustrating the potential structural flexibility of these ligands. Reaction of the amide complex with a bulky monothiol gives a four-coordinate complex with a one-carbon/three-sulfur coordination environment that resembles the resting state of nitrogenase. Reaction of the amide complex with phenylhydrazine gives a product with a rare κ1-bound phenylhydrazido group which undergoes N-N cleavage to give a phenylamido complex.
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Affiliation(s)
- Amy L Speelman
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States
| | - Kazimer L Skubi
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States
| | - Brandon Q Mercado
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States
| | - Patrick L Holland
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States
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Construction of Synthetic Models for Nitrogenase-Relevant NifB Biogenesis Intermediates and Iron-Carbide-Sulfide Clusters. Catalysts 2020. [DOI: 10.3390/catal10111317] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
The family of nitrogenase enzymes catalyzes the reduction of atmospheric dinitrogen (N2) to ammonia under remarkably benign conditions of temperature, pressure, and pH. Therefore, the development of synthetic complexes or materials that can similarly perform this reaction is of critical interest. The primary obstacle for obtaining realistic synthetic models of the active site iron-sulfur-carbide cluster (e.g., FeMoco) is the incorporation of a truly inorganic carbide. This review summarizes the present state of knowledge regarding biological and chemical (synthetic) incorporation of carbide into iron-sulfur clusters. This includes the Nif cluster of proteins and associated biochemistry involved in the endogenous biogenesis of FeMoco. We focus on the chemical (synthetic) incorporation portion of our own efforts to incorporate and modify C1 units in iron/sulfur clusters. We also highlight recent contributions from other research groups in the area toward C1 and/or inorganic carbide insertion.
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Brown AC, Suess DLM. Reversible Formation of Alkyl Radicals at [Fe4S4] Clusters and Its Implications for Selectivity in Radical SAM Enzymes. J Am Chem Soc 2020; 142:14240-14248. [DOI: 10.1021/jacs.0c05590] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Alexandra C. Brown
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Daniel L. M. Suess
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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20
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Kephart JA, Mitchell BS, Chirila A, Anderton KJ, Rogers D, Kaminsky W, Velian A. Atomically Defined Nanopropeller Fe 3Co 6Se 8(Ph 2PNTol) 6: Functional Model for the Electronic Metal-Support Interaction Effect and High Catalytic Activity for Carbodiimide Formation. J Am Chem Soc 2019; 141:19605-19610. [PMID: 31770487 DOI: 10.1021/jacs.9b12473] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Atomically defined interfaces that maximize the density of active sites and harness the electronic metal-support interaction are desirable to facilitate challenging multielectron transformations, but their synthesis remains a considerable challenge. We report the rational synthesis of the atomically defined metal chalcogenide nanopropeller Fe3Co6Se8L6 (L = Ph2PNTol) featuring three Fe edge sites, and its ensuing catalytic activity for carbodiimide formation. The complex interaction between the Fe edges and Co6Se8 support, including the interplay between oxidation state, substrate coordination, and metal-support interaction, is probed in detail using chemical and electrochemical methods, extensive single crystal X-ray diffraction, and electronic absorption and Mössbauer spectroscopy.
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Affiliation(s)
- Jonathan A Kephart
- Department of Chemistry , University of Washington , Seattle , Washington 98195 , United States
| | - Benjamin S Mitchell
- Department of Chemistry , University of Washington , Seattle , Washington 98195 , United States
| | - Andrei Chirila
- Department of Chemistry , University of Washington , Seattle , Washington 98195 , United States
| | - Kevin J Anderton
- Department of Chemistry and Chemical Biology , Harvard University , Cambridge , Massachusetts 02138 , United States
| | - Dylan Rogers
- Department of Chemistry , University of Washington , Seattle , Washington 98195 , United States
| | - Werner Kaminsky
- Department of Chemistry , University of Washington , Seattle , Washington 98195 , United States
| | - Alexandra Velian
- Department of Chemistry , University of Washington , Seattle , Washington 98195 , United States
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Berben LA, Loewen ND. Control of Substrates Beyond the Catalyst Active Site. ACS CENTRAL SCIENCE 2019; 5:1485-1487. [PMID: 31572772 PMCID: PMC6764072 DOI: 10.1021/acscentsci.9b00802] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
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DeRosha DE, Arnet NA, Mercado BQ, Holland PL. A [2Fe-1S] Complex That Affords Access to Bimetallic and Higher-Nuclearity Iron-Sulfur Clusters. Inorg Chem 2019; 58:8829-8834. [PMID: 31247861 DOI: 10.1021/acs.inorgchem.9b01212] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Small, coordinatively unsaturated iron-sulfur clusters are conceived as building blocks for the diverse set of shapes of iron-sulfur clusters in biological and synthetic chemistry. Here we describe a synthetic method for preparing [2Fe-1S] clusters containing two iron(II) ions, which are supported by a relatively unhindered β-diketiminate supporting ligand. The [2Fe-1S] cluster can be isolated in the presence of trimethylphosphine, and the compound with one PMe3 on each iron(II) ion has been crystallographically characterized. The PMe3 ligands may be removed with B(C6F5)3 to give a spectroscopically characterized species with solvent ligands. This species is a versatile synthon for [2Fe-2S], [4Fe-3S], and [10Fe-8S] clusters. Crystallographic characterization of the 10Fe cluster shows that it has all iron(II) ions, and the core has two [4Fe-4S] cubes that share a face in a novel arrangement. This cluster also has two iron sites that are coordinated to solvent donors, suggesting the potential for using this type of cluster for reactivity in the future.
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Affiliation(s)
- Daniel E DeRosha
- Department of Chemistry , Yale University , 225 Prospect Street , New Haven , Connecticut 06511 , United States
| | - Nicholas A Arnet
- Department of Chemistry , Yale University , 225 Prospect Street , New Haven , Connecticut 06511 , United States
| | - Brandon Q Mercado
- Department of Chemistry , Yale University , 225 Prospect Street , New Haven , Connecticut 06511 , United States
| | - Patrick L Holland
- Department of Chemistry , Yale University , 225 Prospect Street , New Haven , Connecticut 06511 , United States
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