1
|
Fraker A, Linn BN, McSkimming A. Low-Coordinate Iron Hydride Chemistry at an N,N,C-Heteroscorpionate Platform. Inorg Chem 2024. [PMID: 39037731 DOI: 10.1021/acs.inorgchem.4c01596] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/23/2024]
Abstract
Locally high-spin iron hydrides are proposed to play a critical role as intermediates in iron-molybdenum cofactor (FeMoco)-catalyzed N2 fixation. Inspired by these biological systems, we report herein our initial investigations into low-coordinate iron hydride chemistry supported by our N,N,C-heteroscorpionate ligands. Those ligands with smaller steric profiles are unable to completely suppress the formation of a binuclear [Fe(μ2-H)]2 complex; however, the incorporation of more substantial steric bulk allows for the isolation of a rare example of a terminal, high-spin (S = 2) Fe2+ hydride. Fourier transform infrared spectroscopy suggests an unusually weak Fe-H bond in the latter molecule. Mössbauer spectroscopies, coupled with density functional theory calculations, highlights the substantial influence of the terminal hydride ligand on 57Fe isomer shift.
Collapse
Affiliation(s)
- Addison Fraker
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Brittany N Linn
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Alex McSkimming
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| |
Collapse
|
2
|
Drena A, Fraker A, Thompson NB, Doan PE, Hoffman BM, McSkimming A. Terminal Hydride Complex of High-Spin Mn. J Am Chem Soc 2024; 146:18370-18378. [PMID: 38940813 PMCID: PMC11240256 DOI: 10.1021/jacs.4c03310] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2024] [Revised: 06/10/2024] [Accepted: 06/12/2024] [Indexed: 06/29/2024]
Abstract
The iron-molybdenum cofactor of nitrogenase (FeMoco) catalyzes fixation of N2 via Fe hydride intermediates. Our understanding of these species has relied heavily on the characterization of well-defined 3d metal hydride complexes, which serve as putative spectroscopic models. Although the Fe ions in FeMoco, a weak-field cluster, are expected to adopt locally high-spin Fe2+/3+ configurations, synthetically accessible hydride complexes featuring d5 or d6 electron counts are almost exclusively low-spin. We report herein the isolation of a terminal hydride complex of four-coordinate, high-spin (d5; S = 5/2) Mn2+. Electron paramagnetic resonance and electron-nuclear double resonance studies reveal an unusually large degree of spin density on the hydrido ligand. In light of the isoelectronic relationship between Mn2+ and Fe3+, our results are expected to inform our understanding of the valence electronic structures of reactive hydride intermediates derived from FeMoco.
Collapse
Affiliation(s)
- Alex Drena
- Department
of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Addison Fraker
- Department
of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| | - Niklas B. Thompson
- Chemical
Sciences and Engineering Division, Argonne
National Laboratory, Lemont, Illinois 60439, United States
| | - Peter E. Doan
- Department
of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Brian M. Hoffman
- Department
of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Alex McSkimming
- Department
of Chemistry, Tulane University, New Orleans, Louisiana 70118, United States
| |
Collapse
|
3
|
Valdez-Moreira JA, Wannipurage DC, Pink M, Carta V, Moënne-Loccoz P, Telser J, Smith JM. Hydrogen atom abstraction by a high spin [Fe III=S] complex. Chem 2023; 9:2601-2609. [PMID: 39021493 PMCID: PMC11251717 DOI: 10.1016/j.chempr.2023.05.007] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/20/2024]
Abstract
Iron sulfur clusters are critical to a plethora of biological processes; however, little is known about the elementary unit of these clusters, namely the [Fe=S]n+ fragment. Here, we report the synthesis and characterization of a terminal iron sulfido complex. Despite its high spin (S = 5/2) ground state, structural, spectroscopic, and computational characterization provide evidence for iron sulfur multiple bond character. Intriguingly, the complex reacts with additional sulfur to afford an S = 3/2 iron(III) disulfido (S2 2-) complex. Preliminary studies reveal that the sulfido complex reacts with dihydroanthracene to afford an iron(II) hydrosulfido complex, akin to the reactivity of iron oxo complexes. By contrast, there is no reaction with the disulfido complex. These results provide important insight into the nature of the iron sulfide unit.
Collapse
Affiliation(s)
| | | | - Maren Pink
- Department of Chemistry, Indiana University, Bloomington, IN 47405, USA
| | - Veronica Carta
- Department of Chemistry, Indiana University, Bloomington, IN 47405, USA
| | - Pierre Moënne-Loccoz
- Department of Chemical Physiology and Biochemistry, School of Medicine, Oregon Health & Science University, Portland, OR 97239, USA
| | - Joshua Telser
- Department of Biological, Physical and Health Sciences, Roosevelt University, Chicago, IL 60605, USA
| | - Jeremy M. Smith
- Department of Chemistry, Indiana University, Bloomington, IN 47405, USA
| |
Collapse
|
4
|
Zars E, Gravogl L, Gau MR, Carroll PJ, Meyer K, Mindiola DJ. Isostructural bridging diferrous chalcogenide cores [Fe II(μ-E)Fe II] (E = O, S, Se, Te) with decreasing antiferromagnetic coupling down the chalcogenide series. Chem Sci 2023; 14:6770-6779. [PMID: 37350823 PMCID: PMC10283490 DOI: 10.1039/d3sc01094e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Accepted: 05/24/2023] [Indexed: 06/24/2023] Open
Abstract
Iron compounds containing a bridging oxo or sulfido moiety are ubiquitous in biological systems, but substitution with the heavier chalcogenides selenium and tellurium, however, is much rarer, with only a few examples reported to date. Here we show that treatment of the ferrous starting material [(tBupyrpyrr2)Fe(OEt2)] (1-OEt2) (tBupyrpyrr2 = 3,5-tBu2-bis(pyrrolyl)pyridine) with phosphine chalcogenide reagents E = PR3 results in the neutral phosphine chalcogenide adduct series [(tBupyrpyrr2)Fe(EPR3)] (E = O, S, Se; R = Ph; E = Te; R = tBu) (1-E) without any electron transfer, whereas treatment of the anionic starting material [K]2[(tBupyrpyrr2)Fe2(μ-N2)] (2-N2) with the appropriate chalcogenide transfer source yields cleanly the isostructural ferrous bridging mono-chalcogenide ate complexes [K]2[(tBupyrpyrr2)Fe2(μ-E)] (2-E) (E = O, S, Se, and Te) having significant deviation in the Fe-E-Fe bridge from linear in the case of E = O to more acute for the heaviest chalcogenide. All bridging chalcogenide complexes were analyzed using a variety of spectroscopic techniques, including 1H NMR, UV-Vis electronic absorbtion, and 57Fe Mössbauer. The spin-state and degree of communication between the two ferrous ions were probed via SQUID magnetometry, where it was found that all iron centers were high-spin (S = 2) FeII, with magnetic exchange coupling between the FeII ions. Magnetic studies established that antiferromagnetic coupling between the ferrous ions decreases as the identity of the chalcogen is tuned from O to the heaviest congener Te.
Collapse
Affiliation(s)
- Ethan Zars
- Department of Chemistry, University of Pennsylvania 231 S 34th St Philadelphia PA 19104 USA
| | - Lisa Gravogl
- Department of Chemistry & Pharmacy, Friedrich-Alexander-Universität Erlangen - Nürnberg (FAU) Egerlandstr. 1 91058 Erlangen Bavaria Germany
| | - Michael R Gau
- Department of Chemistry, University of Pennsylvania 231 S 34th St Philadelphia PA 19104 USA
| | - Patrick J Carroll
- Department of Chemistry, University of Pennsylvania 231 S 34th St Philadelphia PA 19104 USA
| | - Karsten Meyer
- Department of Chemistry & Pharmacy, Friedrich-Alexander-Universität Erlangen - Nürnberg (FAU) Egerlandstr. 1 91058 Erlangen Bavaria Germany
| | - Daniel J Mindiola
- Department of Chemistry, University of Pennsylvania 231 S 34th St Philadelphia PA 19104 USA
| |
Collapse
|
5
|
Construction of a low-valent thiolate-bridged dicobalt platform and its reactivity toward hydrogen activation and evolution. CHINESE CHEM LETT 2022. [DOI: 10.1016/j.cclet.2021.11.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
|
6
|
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.
Collapse
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.
| |
Collapse
|
7
|
Joseph C, Cobb CR, Rose MJ. Single-Step Sulfur Insertions into Iron Carbide Carbonyl Clusters: Unlocking the Synthetic Door to FeMoco Analogues. Angew Chem Int Ed Engl 2021; 60:3433-3437. [PMID: 33089646 DOI: 10.1002/anie.202011517] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2020] [Revised: 10/09/2020] [Indexed: 11/09/2022]
Abstract
The one-step syntheses, X-ray structures, and spectroscopic characterization of synthetic iron clusters, bearing either inorganic sulfides or thiolate with interstitial carbide motifs, are reported. Treatment of iron carbide carbonyl clusters [Fen (μn -C)(CO)m ]x (n=5,6; m=15,16; x=0,-2) with electrophilic sulfur sources (S2 Cl2 , S8 ) results in the formation of several μ4 -S dimers of clusters, and moreover, iron-sulfide-(sulfocarbide) clusters. The core sulfocarbide unit {C-S}4- serves as a structural model for a proposed intermediate in the radical S-adenosyl-L-methionine biogenesis of the M-cluster. Furthermore, the electrophilic sulfur strategy has been extended to provide the first ever thiolato-iron-carbide complex: an analogous reaction with toluylsulfenyl chloride affords the cluster [Fe5 (μ5 -C)(SC7 H7 )(CO)13 ]- . The strategy described herein provides a breakthrough towards developing syntheses of biomimetic iron-sulfur-carbide clusters like FeMoco.
Collapse
Affiliation(s)
- Chris Joseph
- Department of Chemistry, The University of Texas at Austin, Austin, TX, 78712, USA
| | - Caitlyn R Cobb
- Department of Chemistry, The University of Texas at Austin, Austin, TX, 78712, USA
| | - Michael J Rose
- Department of Chemistry, The University of Texas at Austin, Austin, TX, 78712, USA
| |
Collapse
|
8
|
Joseph C, Cobb CR, Rose MJ. Single‐Step Sulfur Insertions into Iron Carbide Carbonyl Clusters: Unlocking the Synthetic Door to FeMoco Analogues. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202011517] [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)
- Chris Joseph
- Department of Chemistry The University of Texas at Austin Austin TX 78712 USA
| | - Caitlyn R. Cobb
- Department of Chemistry The University of Texas at Austin Austin TX 78712 USA
| | - Michael J. Rose
- Department of Chemistry The University of Texas at Austin Austin TX 78712 USA
| |
Collapse
|
9
|
Bai X, Mei T, Yang D, Su L, Wang B, Qu J. Synthesis, characterization and reactivity toward small molecules of a diiron tetrahydrido bridged complex. INORG CHEM COMMUN 2020. [DOI: 10.1016/j.inoche.2020.108286] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
|
10
|
Tanifuji K, Ohki Y. Metal–Sulfur Compounds in N2 Reduction and Nitrogenase-Related Chemistry. Chem Rev 2020; 120:5194-5251. [DOI: 10.1021/acs.chemrev.9b00544] [Citation(s) in RCA: 66] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Kazuki Tanifuji
- Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, California 92697-3900, United States
| | - Yasuhiro Ohki
- Department of Chemsitry, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
| |
Collapse
|
11
|
Arnett CH, Agapie T. Activation of an Open Shell, Carbyne-Bridged Diiron Complex Toward Binding of Dinitrogen. J Am Chem Soc 2020; 142:10059-10068. [DOI: 10.1021/jacs.0c01896] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Charles H. Arnett
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Theodor Agapie
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| |
Collapse
|
12
|
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.
Collapse
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
| |
Collapse
|
13
|
Bhutto SM, Holland PL. Dinitrogen Activation and Functionalization using β-Diketiminate Iron Complexes. Eur J Inorg Chem 2019; 2019:1861-1869. [PMID: 31213945 DOI: 10.1002/ejic.201900133] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Iron catalysts are adept at breaking the N-N bond of N2, as exemplified by the iron-catalyzed Haber-Bosch process and the iron-containing clusters at the active sites of nitrogenase enzymes. This Minireview summarizes recent work that has identified a well-characterized set of multi-iron complexes that are capable of breaking and functionalizing N2, and are amenable to detailed mechanistic studies. We discuss the redox balancing, the potential intermediates during N2 activation, the variation of alkali metal reductant, the reversibility of N2 cleavage, and the formation of N-H and N-C bonds from N2.
Collapse
Affiliation(s)
- Samuel M Bhutto
- Department of Chemistry, Yale University, 225 Prospect St, New Haven, CT 06520, USA
| | - Patrick L Holland
- Department of Chemistry, Yale University, 225 Prospect St, New Haven, CT 06520, USA
| |
Collapse
|
14
|
Yang D, Xu S, Zhang Y, Li Y, Li Y, Wang B, Qu J. Reactivity toward Unsaturated Small Molecules of Thiolate-Bridged Diiron Hydride Complexes. Inorg Chem 2018; 57:15198-15204. [PMID: 30485081 DOI: 10.1021/acs.inorgchem.8b02459] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In the presence of 1 equiv of tBuNC, the homolytic cleavage of the FeIII-H bond in the diiron terminal hydride complex [Cp*Fe( t-H)(μ-η2:η4-bdt)FeCp*][BF4] (1[BF4]) smoothly took place to release 1/2 H2, followed by binding of a tBuNC group to the unsaturated FeII center. Interestingly, upon exposure of 1[BF4] to 1 atm of acetylene, the isomerization process of the hydride ligand from the terminal to bridging coordination site was unaffected. Upon treatment of the diiron hydride bridged complex 2[BF4] with acetylene at 30 °C, two FeIII-H bonds were broken, and then an acetylene molecule was coordinated to the diiron centers in a novel μ-η2:η2 side-on fashion. In the above reaction system, the hydride ligands whether terminal or bridging all play a role as the electron donor for the reduction of the diiron centers from FeIIIFeIII to FeIIIFeII. These reaction patterns are reminiscent of the vital E4 state responsible for N2 binding and H2 liberation in the catalytic cycle of nitrogenase, which contains two {Fe-H-Fe} motifs as electron reservoirs for the reduction of the iron centers. Differently, when treating 1[BF4] with TMSN3, the terminal hydride ligand was inserted into the azide group to give a diiron amide complex 4[BF4] in moderate yield.
Collapse
Affiliation(s)
- Dawei Yang
- State Key Laboratory of Fine Chemicals , Dalian University of Technology , Dalian 116024 , People's Republic of China
| | - Sunlin Xu
- State Key Laboratory of Fine Chemicals , Dalian University of Technology , Dalian 116024 , People's Republic of China
| | - Yixin Zhang
- State Key Laboratory of Fine Chemicals , Dalian University of Technology , Dalian 116024 , People's Republic of China
| | - Ying Li
- State Key Laboratory of Fine Chemicals , Dalian University of Technology , Dalian 116024 , People's Republic of China
| | - Yang Li
- State Key Laboratory of Fine Chemicals , Dalian University of Technology , Dalian 116024 , People's Republic of China
| | - Baomin Wang
- State Key Laboratory of Fine Chemicals , Dalian University of Technology , Dalian 116024 , People's Republic of China
| | - Jingping Qu
- State Key Laboratory of Fine Chemicals , Dalian University of Technology , Dalian 116024 , People's Republic of China.,Key Laboratory for Advanced Materials , East China University of Science and Technology , Shanghai , 200237 , People's Republic of China
| |
Collapse
|
15
|
Su L, Yang D, Zhang Y, Wang B, Qu J. Methylene insertion into an Fe 2S 2 cluster: formation of a thiolate-bridged diiron complex containing an Fe-CH 2-S moiety. Chem Commun (Camb) 2018; 54:13119-13122. [PMID: 30398494 DOI: 10.1039/c8cc07418f] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Reduction of a thiolate-bridged FeIIFeIII complex leads to the cleavage of an Fe-S bond by the insertion of the methylene unit from CH2Cl2 to give a neutral FeIIFeIII complex with a novel Fe-CH2-S fragment. The structural and electrochemical differences of the alkylated and the non-alkylated Fe2S2 complexes are also examined.
Collapse
Affiliation(s)
- Linan Su
- State Key Laboratory of Fine Chemicals, Dalian University of Technology, 2 Linggong Road, Dalian 116024, P. R. China.
| | | | | | | | | |
Collapse
|
16
|
Foster SL, Bakovic SIP, Duda RD, Maheshwari S, Milton RD, Minteer SD, Janik MJ, Renner JN, Greenlee LF. Catalysts for nitrogen reduction to ammonia. Nat Catal 2018. [DOI: 10.1038/s41929-018-0092-7] [Citation(s) in RCA: 676] [Impact Index Per Article: 112.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
|
17
|
Broere DLJ, Mercado BQ, Lukens JT, Vilbert AC, Banerjee G, Lant HMC, Lee SH, Bill E, Sproules S, Lancaster KM, Holland PL. Reversible Ligand-Centered Reduction in Low-Coordinate Iron Formazanate Complexes. Chemistry 2018; 24:9417-9425. [PMID: 29663542 PMCID: PMC6115202 DOI: 10.1002/chem.201801298] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2018] [Indexed: 02/01/2023]
Abstract
Coordination of redox-active ligands to metals is a compelling strategy for making reduced complexes more accessible. In this work, we explore the use of redox-active formazanate ligands in low-coordinate iron chemistry. Reduction of an iron(II) precursor occurs at milder potentials than analogous non-redox-active β-diketiminate complexes, and the reduced three-coordinate formazanate-iron compound is characterized in detail. Structural, spectroscopic, and computational analysis show that the formazanate ligand undergoes reversible ligand-centered reduction to form a formazanate radical dianion in the reduced species. The less negative reduction potential of the reduced low-coordinate iron formazanate complex leads to distinctive reactivity with formation of a new N-I bond that is not seen with the β-diketiminate analogue. Thus, the storage of an electron on the supporting ligand changes the redox potential and enhances certain reactivity.
Collapse
Affiliation(s)
- Daniel L. J. Broere
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States, /
| | - Brandon Q. Mercado
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States, /
| | - James T. Lukens
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca New York 14853
| | - Avery C. Vilbert
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca New York 14853
| | - Gourab Banerjee
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States, /
| | - Hannah M. C. Lant
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States, /
| | - Shin Hee Lee
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States, /
| | - Eckhard Bill
- Max Planck Institute for Chemical Energy Conversion, Stiftstrasse 34-36, D-45470 Mülheim an der Ruhr, Germany
| | - Stephen Sproules
- WestCHEM, School of Chemistry, University of Glasgow, Glasgow G12 8QQ, United Kingdom
| | - Kyle M. Lancaster
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca New York 14853
| | - Patrick L. Holland
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States, /
| |
Collapse
|
18
|
Arnett CH, Chalkley MJ, Agapie T. A Thermodynamic Model for Redox-Dependent Binding of Carbon Monoxide at Site-Differentiated, High Spin Iron Clusters. J Am Chem Soc 2018; 140:5569-5578. [PMID: 29589921 PMCID: PMC6452638 DOI: 10.1021/jacs.8b01825] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Binding of N2 and CO by the FeMo-cofactor of nitrogenase depends on the redox level of the cluster, but the extent to which pure redox chemistry perturbs the affinity of high spin iron clusters for π-acids is not well understood. Here, we report a series of site-differentiated iron clusters that reversibly bind CO in redox states FeII4 through FeIIFeIII3. One electron redox events result in small changes in the affinity for (at most ∼400-fold) and activation of CO (at most 28 cm-1 for νCO). The small influence of redox chemistry on the affinity of these high spin, valence-localized clusters for CO is in stark contrast to the large enhancements (105-1022 fold) in π-acid affinity reported for monometallic and low spin, bimetallic iron complexes, where redox chemistry occurs exclusively at the ligand binding site. While electron-loading at metal centers remote from the substrate binding site has minimal influence on the CO binding energetics (∼1 kcal·mol-1), it provides a conduit for CO binding at an FeIII center. Indeed, internal electron transfer from these remote sites accommodates binding of CO at an FeIII, with a small energetic penalty arising from redox reorganization (∼2.6 kcal·mol-1). The ease with which these clusters redistribute electrons in response to ligand binding highlights a potential pathway for coordination of N2 and CO by FeMoco, which may occur on an oxidized edge of the cofactor.
Collapse
Affiliation(s)
- Charles H. Arnett
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Matthew J. Chalkley
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Theodor Agapie
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| |
Collapse
|
19
|
Sagawa T, Tsukada S, Yamamoto K, Gunji T. Synthesis and reactivity of hydride-bridged ruthenium dithiolene complexes. Polyhedron 2018. [DOI: 10.1016/j.poly.2017.10.023] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
20
|
Arnet NA, McWilliams SF, DeRosha DE, Mercado BQ, Holland PL. Synthesis and Mechanism of Formation of Hydride-Sulfide Complexes of Iron. Inorg Chem 2017; 56:9185-9193. [PMID: 28726395 DOI: 10.1021/acs.inorgchem.7b01230] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Iron-sulfide complexes with hydride ligands provide an experimental precedent for spectroscopically detected hydride species on the iron-sulfur MoFe7S9C cofactor of nitrogenase. In this contribution, we expand upon our recent synthesis of the first iron sulfide hydride complex from an iron hydride and a sodium thiolate ( Arnet, N. A.; Dugan, T. R.; Menges, F. S.; Mercado, B. Q.; Brennessel, W. W.; Bill, E.; Johnson, M. A.; Holland, P. L., J. Am. Chem. Soc. 2015 , 137 , 13220 - 13223 ). First, we describe the isolation of an analogous iron sulfide hydride with a smaller diketiminate supporting ligand, which benefits from easier preparation of the hydride precursor and easier isolation of the product. Second, we describe mechanistic studies on the C-S bond cleavage through which the iron sulfide hydride product is formed. In a key experiment, use of cyclopropylmethanethiolate as the sulfur precursor leads to products from cyclopropane ring opening, implicating an alkyl radical as an intermediate. Combined with the results of isotopic labeling studies, the data are consistent with a mechanism in which homolytic C-S bond cleavage is followed by rebound of the alkyl radical to abstract a hydrogen atom from iron to give the observed alkane and iron-sulfide products.
Collapse
Affiliation(s)
- Nicholas A Arnet
- Department of Chemistry, Yale University , 225 Prospect Street, New Haven, Connecticut 06511, United States
| | - Sean F McWilliams
- Department of Chemistry, Yale University , 225 Prospect Street, New Haven, Connecticut 06511, United States
| | - Daniel E DeRosha
- 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
| |
Collapse
|
21
|
Čorić I, Holland PL. Insight into the Iron-Molybdenum Cofactor of Nitrogenase from Synthetic Iron Complexes with Sulfur, Carbon, and Hydride Ligands. J Am Chem Soc 2016; 138:7200-11. [PMID: 27171599 PMCID: PMC5508211 DOI: 10.1021/jacs.6b00747] [Citation(s) in RCA: 118] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Nitrogenase enzymes are used by microorganisms for converting atmospheric N2 to ammonia, which provides an essential source of N atoms for higher organisms. The active site of the molybdenum-dependent nitrogenase is the unique carbide-containing iron-sulfur cluster called the iron-molybdenum cofactor (FeMoco). On the FeMoco, N2 binding is suggested to occur at one or more iron atoms, but the structures of the catalytic intermediates are not clear. In order to establish the feasibility of different potential mechanistic steps during biological N2 reduction, chemists have prepared iron complexes that mimic various structural aspects of the iron sites in the FeMoco. This reductionist approach gives mechanistic insight, and also uncovers fundamental principles that could be used more broadly for small-molecule activation. Here, we discuss recent results and highlight directions for future research. In one direction, synthetic iron complexes have now been shown to bind N2, break the N-N triple bond, and produce ammonia catalytically. Carbon- and sulfur-based donors have been incorporated into the ligand spheres of Fe-N2 complexes to show how these atoms may influence the structure and reactivity of the FeMoco. Hydrides have been incorporated into synthetic systems, which can bind N2, reduce some nitrogenase substrates, and/or reductively eliminate H2 to generate reduced iron centers. Though some carbide-containing iron clusters are known, none yet have sulfide bridges or high-spin iron atoms like the FeMoco.
Collapse
Affiliation(s)
- Ilija Čorić
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| | - Patrick L. Holland
- Department of Chemistry, Yale University, New Haven, Connecticut 06520, United States
| |
Collapse
|
22
|
McKee ML. A New Nitrogenase Mechanism Using a CFe8S9 Model: Does H2 Elimination Activate the Complex to N2 Addition to the Central Carbon Atom? J Phys Chem A 2016; 120:754-64. [PMID: 26821350 DOI: 10.1021/acs.jpca.5b10384] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
A truncated model of the FeMo cofactor is used to explore a new mechanism for the conversion of N2 to NH3 by the nitrogenase enzyme. After four initial protonation/reduction steps, the H4CFe8S9 cluster has two hydrogen atoms attached to sulfur, one hydrogen bridging two iron centers and one hydrogen bonded to carbon. The loss of the CH and FeHFe hydrogens as molecular hydrogen activates the cluster to addition of N2 to the carbon center. This unique step takes place at a nearly planar four-coordinate carbon center and leads to an intermediate with a significantly weakened N-N bond. A hydrogen attached to a sulfur atom is then transferred to the distal nitrogen atom. Additional prontonation/reduction steps are modeled by adding a hydrogen atom to sulfur and locating the transition states for transfer to nitrogen. The first NH3 is lost in a thermal neutral step, while the second step is endothermic. The loss of H2 activates the complex by reducing the barrier for N2 addition by 3.5 kcal/mol. Since this is the most difficult step in the mechanism, reducing the barrier for this step justifies the "extra expense" of H2 production.
Collapse
Affiliation(s)
- Michael L McKee
- Department of Chemistry and Biochemistry, Auburn University , Auburn, Alabama 36849, United States
| |
Collapse
|
23
|
Goodman C. A hydride out of hiding. Nat Chem Biol 2015. [DOI: 10.1038/nchembio.1971] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|