1
|
Pérez-González A, Yang ZY, Lukoyanov DA, Dean DR, Seefeldt LC, Hoffman BM. Exploring the Role of the Central Carbide of the Nitrogenase Active-Site FeMo-cofactor through Targeted 13C Labeling and ENDOR Spectroscopy. J Am Chem Soc 2021; 143:9183-9190. [PMID: 34110795 DOI: 10.1021/jacs.1c04152] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Mo-dependent nitrogenase is a major contributor to global biological N2 reduction, which sustains life on Earth. Its multi-metallic active-site FeMo-cofactor (Fe7MoS9C-homocitrate) contains a carbide (C4-) centered within a trigonal prismatic CFe6 core resembling the structural motif of the iron carbide, cementite. The role of the carbide in FeMo-cofactor binding and activation of substrates and inhibitors is unknown. To explore this role, the carbide has been in effect selectively enriched with 13C, which enables its detailed examination by ENDOR/ESEEM spectroscopies. 13C-carbide ENDOR of the S = 3/2 resting state (E0) is remarkable, with an extremely small isotropic hyperfine coupling constant, Ca = +0.86 MHz. Turnover under high CO partial pressure generates the S = 1/2 hi-CO state, with two CO molecules bound to FeMo-cofactor. This conversion surprisingly leaves the small magnitude of the 13C carbide isotropic hyperfine-coupling constant essentially unchanged, Ca = -1.30 MHz. This indicates that both the E0 and hi-CO states exhibit an exchange-coupling scheme with nearly cancelling contributions to Ca from three spin-up and three spin-down carbide-bound Fe ions. In contrast, the anisotropic hyperfine coupling constant undergoes a symmetry change upon conversion of E0 to hi-CO that may be associated with bonding and coordination changes at Fe ions. In combination with the negligible difference between CFe6 core structures of E0 and hi-CO, these results suggest that in CO-inhibited hi-CO the dominant role of the FeMo-cofactor carbide is to maintain the core structure, rather than to facilitate inhibitor binding through changes in Fe-carbide covalency or stretching/breaking of carbide-Fe bonds.
Collapse
Affiliation(s)
- Ana Pérez-González
- Department of Biochemistry, Virginia Tech, Blacksburg, Virginia 24061, United States
| | - Zhi-Yong Yang
- Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, United States
| | - Dmitriy A Lukoyanov
- Department of Chemistry Northwestern University, Evanston, Illinois 60208, United States
| | - Dennis R Dean
- Department of Biochemistry, Virginia Tech, Blacksburg, Virginia 24061, United States
| | - Lance C Seefeldt
- Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, United States
| | - Brian M Hoffman
- Department of Chemistry Northwestern University, Evanston, Illinois 60208, United States
| |
Collapse
|
2
|
Stennett CR, Fettinger JC, Power PP. Low-Coordinate Iron Chalcogenolates and Their Complexes with Diethyl Ether and Ammonia. Inorg Chem 2021; 60:6712-6720. [PMID: 33848423 DOI: 10.1021/acs.inorgchem.1c00539] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Treatment of Fe{N(SiMe3)2}2 with 2 equiv of the appropriate phenol or thiol affords the dimers {Fe(OC6H2-2,6-But2-4-Me)2}2 (1) and {Fe(OC6H3-2,6-But2)2}2 (2) or the monomeric Fe{SC6H3-2,6-(C6H3-2,6-Pri2)2}2 (3) in moderate to excellent yields. Recrystallization of 1 and 2 from diethyl ether gives the corresponding three-coordinate ether complexes Fe(OC6H3-2,6-But2-4-Me)2(OEt2) (4) and Fe(OC6H3-2,6-But2)2(OEt2) (5). In contrast, no diethyl ether complex is formed by the dithiolate 3. The 1H NMR spectra of 4 and 5 show equilibria between the ether complexes and the base-free dimers. A comparison of these spectra with those of the dimeric 1 and 2 allows an unambiguous assignment of the paramagnetically shifted signals. Treatment of 1 with excess ammonia gives the tetrahedral diammine Fe(OC6H2-2,6-But2-4-Me)2(NH3)2 (6). Ammonia is strongly coordinated in 6, with no apparent loss of ammine ligand either in solution or upon heating under low pressure. In contrast, significantly weaker ammonia coordination is observed when dithiolate 3 is treated with excess ammonia, which gives the diammine Fe{SC6H3-2,6-(2,6-Pri2-C6H3)2}2(NH3)2 (7). Complex 7 readily loses ammonia either in solution or under reduced pressure to give the monoammine complex Fe{SC6H3-2,6-(2,6-Pri2-C6H3)2}2(NH3) (8). The weak binding of ammonia by iron thiolate 7 reflects the likely behavior of the proposed iron-sulfur active site in nitrogenases, where release of ammonia is required to close the catalytic cycle.
Collapse
Affiliation(s)
- Cary R Stennett
- Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, California 95616, United States
| | - James C Fettinger
- Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, California 95616, United States
| | - Philip P Power
- Department of Chemistry, University of California, Davis, One Shields Avenue, Davis, California 95616, United States
| |
Collapse
|
3
|
Chalkley MJ, Drover MW, Peters JC. Catalytic N 2-to-NH 3 (or -N 2H 4) Conversion by Well-Defined Molecular Coordination Complexes. Chem Rev 2020; 120:5582-5636. [PMID: 32352271 DOI: 10.1021/acs.chemrev.9b00638] [Citation(s) in RCA: 185] [Impact Index Per Article: 46.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Nitrogen fixation, the six-electron/six-proton reduction of N2, to give NH3, is one of the most challenging and important chemical transformations. Notwithstanding the barriers associated with this reaction, significant progress has been made in developing molecular complexes that reduce N2 into its bioavailable form, NH3. This progress is driven by the dual aims of better understanding biological nitrogenases and improving upon industrial nitrogen fixation. In this review, we highlight both mechanistic understanding of nitrogen fixation that has been developed, as well as advances in yields, efficiencies, and rates that make molecular alternatives to nitrogen fixation increasingly appealing. We begin with a historical discussion of N2 functionalization chemistry that traverses a timeline of events leading up to the discovery of the first bona fide molecular catalyst system and follow with a comprehensive overview of d-block compounds that have been targeted as catalysts up to and including 2019. We end with a summary of lessons learned from this significant research effort and last offer a discussion of key remaining challenges in the field.
Collapse
Affiliation(s)
- Matthew J Chalkley
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Marcus W Drover
- 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
| |
Collapse
|
4
|
Sorsche D, Miehlich ME, Searles K, Gouget G, Zolnhofer EM, Fortier S, Chen CH, Gau M, Carroll PJ, Murray CB, Caulton KG, Khusniyarov MM, Meyer K, Mindiola DJ. Unusual Dinitrogen Binding and Electron Storage in Dinuclear Iron Complexes. J Am Chem Soc 2020; 142:8147-8159. [DOI: 10.1021/jacs.0c01488] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Affiliation(s)
- Dieter Sorsche
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Matthias E. Miehlich
- Inorganic Chemistry, Department of Chemistry and Pharmacy, Friedrich-Alexander University Erlangen-Nürnberg, 91058 Erlangen, Germany
| | - Keith Searles
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
- Department of Chemistry and Molecular Structure Center, Indiana University, Bloomington, Indiana 47405, United States
| | - Guillaume Gouget
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Eva M. Zolnhofer
- Inorganic Chemistry, Department of Chemistry and Pharmacy, Friedrich-Alexander University Erlangen-Nürnberg, 91058 Erlangen, Germany
| | - Skye Fortier
- Department of Chemistry and Molecular Structure Center, Indiana University, Bloomington, Indiana 47405, United States
| | - Chun-Hsing Chen
- Department of Chemistry and Molecular Structure Center, Indiana University, Bloomington, Indiana 47405, United States
| | - Michael Gau
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Patrick J. Carroll
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Christopher B. Murray
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| | - Kenneth G. Caulton
- Department of Chemistry and Molecular Structure Center, Indiana University, Bloomington, Indiana 47405, United States
| | - Marat M. Khusniyarov
- Inorganic Chemistry, Department of Chemistry and Pharmacy, Friedrich-Alexander University Erlangen-Nürnberg, 91058 Erlangen, Germany
| | - Karsten Meyer
- Inorganic Chemistry, Department of Chemistry and Pharmacy, Friedrich-Alexander University Erlangen-Nürnberg, 91058 Erlangen, Germany
| | - Daniel J. Mindiola
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, United States
| |
Collapse
|
5
|
Speelman AL, Čorić I, Van Stappen C, DeBeer S, Mercado BQ, Holland PL. Nitrogenase-Relevant Reactivity of a Synthetic Iron-Sulfur-Carbon Site. J Am Chem Soc 2019; 141:13148-13157. [PMID: 31403298 DOI: 10.1021/jacs.9b05353] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Simple synthetic compounds with only S and C donors offer a ligation environment similar to the active site of nitrogenase (FeMoco) and thus demonstrate reasonable mechanisms and geometries for N2 binding and reduction in nature. We recently reported the first example of N2 binding at a mononuclear iron site supported by only S and C donors. In this work, we report experiments that examine the mechanism of N2 binding in this system. The reduction of an iron(II) tris(thiolate) complex with 1 equiv of KC8 leads to a thermally unstable intermediate, and a combination of Mössbauer, EPR, and X-ray absorption spectroscopies identifies it as a high-spin (S = 3/2) iron(I) species that maintains coordination of all three sulfur atoms. DFT calculations suggest that this iron(I) intermediate has a pseudotetrahedral geometry that resembles the S3C iron coordination environment of the belt iron sites in the resting state of the FeMoco. Further reduction to the iron(0) oxidation level under argon causes the dissociation of one of the thiolate donors and gives an η6-arene species which reacts with N2. Thus, in this system the loss of thiolate and binding of N2 require reduction beyond the iron(I) level to the iron(0) level. Further reduction of the iron(0)-N2 complex gives a reactive, formally iron(-I) species. Treatment of the putative iron(-I) complex with weak acids gives low yields of ammonia and hydrazine, demonstrating that these nitrogenase products can be generated from N2 at a synthetic Fe-S-C site. Catalytic N2 reduction is not observed, which is attributed to protonation of the supporting ligand and degradation of the complex via ligand dissociation. Identification of the challenges in this system gives insight into the design features needed for functional biomimetic complexes.
Collapse
Affiliation(s)
- Amy L Speelman
- Department of Chemistry , Yale University , 225 Prospect Street , New Haven , Connecticut 06520 , United States
| | - Ilija Čorić
- Department of Chemistry , Yale University , 225 Prospect Street , New Haven , Connecticut 06520 , United States
| | - Casey Van Stappen
- Max Planck Institute for Chemical Energy Conversion , Stiftstraße 34-36 , D-45470 Mülheim an der Ruhr , Germany
| | - Serena DeBeer
- Max Planck Institute for Chemical Energy Conversion , Stiftstraße 34-36 , D-45470 Mülheim an der Ruhr , Germany
| | - 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
| |
Collapse
|
6
|
Grubba R, Kaniewska K, Ponikiewski Ł, Cristóvão B, Ferenc W, Dragulescu-Andrasi A, Krzystek J, Stoian SA, Pikies J. Synthetic, Structural, and Spectroscopic Characterization of a Novel Family of High-Spin Iron(II) [(β-Diketiminate)(phosphanylphosphido)] Complexes. Inorg Chem 2017; 56:11030-11042. [PMID: 28841309 DOI: 10.1021/acs.inorgchem.7b01374] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
This work describes a series of iron(II) phosphanylphosphido complexes. These compounds were obtained by reacting lithiated diphosphanes R2PP(SiMe3)Li (R = t-Bu, i-Pr) with an iron(II) β-diketiminate complex, [LFe(μ2-Cl)2Li(DME)2] (1), where DME = 1,2-dimethoxyethane and L = Dippnacnac (β-diketiminate). While the reaction of 1 with t-Bu2PP(SiMe3)Li yields [LFe(η1-Me3SiPP-t-Bu2)] (2), that of 1 with equimolar amounts of i-Pr2PP(SiMe3)Li, in DME, leads to [LFe(η2-i-Pr2PPSiMe3)] (3). In contrast, the reaction of 1 with (i-Pr2N)2PP(SiMe3)Li provides not an iron-containing complex but 1-[(diisopropylamino)phosphine]-2,4-bis(diisopropylamino)-3-(trimethylsilyl)tetraphosphetane (4). The structures of 2-4 were determined using diffractometry. Thus, 2 exhibits a three-coordinate iron site and 3 a four-coordinate iron site. The increase in the coordination number is induced by the change from an anticlinal to a synclinal conformation of the phoshpanylphosphido ligands. The electronic structures of 2 and 3 were assessed through a combined field-dependent 57Fe Mössbauer and high-frequency and -field electron paramagnetic resonance spectroscopic investigation in conjunction with analysis of their magnetic susceptibility and magnetization data. These studies revealed two high-spin iron(II) sites with S = 2 ground states that have different properties. While 2 exhibits a zero-field splitting described by a positive D parameter (D = +17.4 cm-1; E/D = 0.11) for 3, this parameter is negative [D = -25(5) cm-1; E/D = 0.15(5)]. Density functional theory (DFT) and time-dependent DFT (TDDFT) calculations provide insights into the origin of these differences and allow us to rationalize the fine and hyperfine structure parameters of 2 and 3. Thus, for 2, the spin-orbit coupling mixes a z2-type ground state with two low-lying {xz/yz} orbital states. These interactions lead to an easy plane of magnetization, which is essentially parallel to the plane defined by the N-Fe-N atoms. For 3, we find a yz-type ground state that is strongly mixed with a low-lying z2-type orbital state. In this case, the spin-orbit interaction leads to a partial unquenching of the orbital momentum along the x axis, that is, to an easy axis of magnetization oriented roughly along the Fe-P bond of the phosphido moiety.
Collapse
Affiliation(s)
- Rafał Grubba
- Department of Inorganic Chemistry, Chemical Faculty, Gdańsk University of Technology , G. Narutowicza St. 11/12, Gdańsk PL-80-233, Poland
| | - Kinga Kaniewska
- Department of Inorganic Chemistry, Chemical Faculty, Gdańsk University of Technology , G. Narutowicza St. 11/12, Gdańsk PL-80-233, Poland
| | - Łukasz Ponikiewski
- Department of Inorganic Chemistry, Chemical Faculty, Gdańsk University of Technology , G. Narutowicza St. 11/12, Gdańsk PL-80-233, Poland
| | - Beata Cristóvão
- Department of General and Coordination Chemistry, Faculty of Chemistry, Maria Curie-Skłodowska University , Maria Curie-Skłodowska Sq. 2, Lublin PL-20-031, Poland
| | - Wiesława Ferenc
- Department of General and Coordination Chemistry, Faculty of Chemistry, Maria Curie-Skłodowska University , Maria Curie-Skłodowska Sq. 2, Lublin PL-20-031, Poland
| | - Alina Dragulescu-Andrasi
- Department of Chemistry and Biochemistry, Florida State University , Tallahassee, Florida 32306, United States
| | - J Krzystek
- National High Magnetic Field Laboratory, Florida State University , Tallahassee, Florida 32310, United States
| | - Sebastian A Stoian
- Department of Chemistry and Biochemistry, Florida State University , Tallahassee, Florida 32306, United States.,National High Magnetic Field Laboratory, Florida State University , Tallahassee, Florida 32310, United States.,Department of Chemistry, University of Idaho , Moscow, Idaho 83844, United States
| | - Jerzy Pikies
- Department of Inorganic Chemistry, Chemical Faculty, Gdańsk University of Technology , G. Narutowicza St. 11/12, Gdańsk PL-80-233, Poland
| |
Collapse
|
7
|
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
|
8
|
MacLeod KC, McWilliams SF, Mercado BQ, Holland PL. Stepwise N-H Bond Formation From N 2-Derived Iron Nitride, Imide and Amide Intermediates to Ammonia. Chem Sci 2016; 7:5736-5746. [PMID: 28066537 PMCID: PMC5207225 DOI: 10.1039/c6sc00423g] [Citation(s) in RCA: 66] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Reduction of N2 to ammonia in nature and in electrocatalysis takes place through 1-proton/1-electron steps, motivating efforts to experimentally study the steps during proton/electron transfer to well-characterized N2-derived species with bridging nitrides. We report here the protonation and reduction reactions of an N2-derived iron bis(nitride) complex (Rodriguez et al., Science, 2011, 334, 780). We isolate and definitively characterize triiron imido and amido intermediates that lie along the path to ammonia formation, and Mössbauer spectroscopy shows the oxidation level of iron atoms in these mixed-valence clusters. The first two H atoms add to one of the two nitrides of the bis(nitride) complex, and the proton-coupled electron transfer in the second step can be concerted or stepwise depending on the sources of protons and electrons. The characterization of partially protonated nitrides and their mechanisms of formation are expected to guide efforts to convert N2 to ammonia with mild acids.
Collapse
Affiliation(s)
- K Cory MacLeod
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States
| | - Sean F McWilliams
- 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
| |
Collapse
|
9
|
Čorić I, Mercado BQ, Bill E, Vinyard DJ, Holland PL. Binding of dinitrogen to an iron-sulfur-carbon site. Nature 2015; 526:96-9. [PMID: 26416755 PMCID: PMC4592811 DOI: 10.1038/nature15246] [Citation(s) in RCA: 143] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2015] [Accepted: 07/24/2015] [Indexed: 01/25/2023]
Abstract
Nitrogenases are the enzymes by which certain microorganisms convert atmospheric dinitrogen (N2) to ammonia, thereby providing essential nitrogen atoms for higher organisms. The most common nitrogenases reduce atmospheric N2 at the FeMo cofactor, a sulfur-rich iron-molybdenum cluster (FeMoco). The central iron sites that are coordinated to sulfur and carbon atoms in FeMoco have been proposed to be the substrate binding sites, on the basis of kinetic and spectroscopic studies. In the resting state, the central iron sites each have bonds to three sulfur atoms and one carbon atom. Addition of electrons to the resting state causes the FeMoco to react with N2, but the geometry and bonding environment of N2-bound species remain unknown. Here we describe a synthetic complex with a sulfur-rich coordination sphere that, upon reduction, breaks an Fe-S bond and binds N2. The product is the first synthetic Fe-N2 complex in which iron has bonds to sulfur and carbon atoms, providing a model for N2 coordination in the FeMoco. Our results demonstrate that breaking an Fe-S bond is a chemically reasonable route to N2 binding in the FeMoco, and show structural and spectroscopic details for weakened N2 on a sulfur-rich iron site.
Collapse
Affiliation(s)
- Ilija Čorić
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, USA
| | - Brandon Q Mercado
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, USA
| | - Eckhard Bill
- Max Planck Institute for Chemical Energy Conversion, Stiftstrasse 34-36, D-45470 Mülheim an der Ruhr, Germany
| | - David J Vinyard
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, USA
| | - Patrick L Holland
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, USA
| |
Collapse
|
10
|
Suzuki T, Wasada-Tsutsui Y, Ogawa T, Inomata T, Ozawa T, Sakai Y, Fryzuk MD, Masuda H. N2 activation by an iron complex with a strong electron-donating iminophosphorane ligand. Inorg Chem 2015; 54:9271-81. [PMID: 26135343 DOI: 10.1021/acs.inorgchem.5b00536] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A new tridentate cyclopentane-bridged iminophosphorane ligand, N-(2-diisopropylphosphinophenyl)-P,P-diisopropyl-P-(2-(2,6-diisopropylphenylamido)cyclopent-1-enyl)phosphoranimine (NpNPiPr), was synthesized and used in the preparation of a diiron dinitrogen complex. The reaction of the iron complex FeBr(NpNPiPr) with KC8 under dinitrogen yielded the dinuclear dinitrogen Fe complex [Fe(NpNPiPr)]2(μ-N2), which was characterized by X-ray analysis and resonance Raman and NMR spectroscopies. The X-ray analysis revealed a diiron complex bridged by the dinitrogen molecule, with each metal center coordinated by an NpNPiPr ligand and dinitrogen in a trigonal-monopyramidal geometry. The N–N bond length is 1.184(6) Å, and resonance Raman spectra indicate that the N–N stretching mode ν(14N2/15N2) is 1755/1700 cm–1. The magnetic moment of [Fe(NpNPiPr)]2(μ-N2) in benzene-d6 solution, as measured by 1H NMR spectroscopy by the Evans method, is 6.91μB (S = 3). The Mössbauer spectrum at 78 K showed δ = 0.73 mm/s and ΔEQ = 1.83 mm/s. These findings suggest that the iron ions are divalent with a high-spin configuration and that the N2 molecule has (N═N)2– character. Density functional theory calculations performed on [Fe(NpNPiPr)]2(μ-N2) also suggested that the iron is in a high-spin divalent state and that the coordinated dinitrogen molecule is effectively activated by π back-donation from the two iron ions (dπ) to the dinitrogen molecule (πx* and πy*). This is supported by cooperation between a large negative charge on the iminophosphorane ligand and strong electron donation and effective orbital overlap between the iron dπ orbitals and N2 π* orbitals supplied by the phosphine ligand.
Collapse
Affiliation(s)
- Tatsuya Suzuki
- Department of Frontier Materials, Graduate School of Engineering, Nagoya Institute of Technology , Gokiso, Showa, Nagoya 466-8555, Japan.,Department of Chemistry, The University of British Columbia , 2036 Main Mall, Vancouver, British Columbia, Canada V6T 1Z1
| | - Yuko Wasada-Tsutsui
- Department of Frontier Materials, Graduate School of Engineering, Nagoya Institute of Technology , Gokiso, Showa, Nagoya 466-8555, Japan
| | - Takahiko Ogawa
- Department of Frontier Materials, Graduate School of Engineering, Nagoya Institute of Technology , Gokiso, Showa, Nagoya 466-8555, Japan
| | - Tomohiko Inomata
- Department of Frontier Materials, Graduate School of Engineering, Nagoya Institute of Technology , Gokiso, Showa, Nagoya 466-8555, Japan
| | - Tomohiro Ozawa
- Department of Frontier Materials, Graduate School of Engineering, Nagoya Institute of Technology , Gokiso, Showa, Nagoya 466-8555, Japan
| | - Yoichi Sakai
- Department of Chemistry, Daido University , Takiharu-cho, Minami-ku, Nagoya 457-8530, Japan
| | - Michael D Fryzuk
- Department of Chemistry, The University of British Columbia , 2036 Main Mall, Vancouver, British Columbia, Canada V6T 1Z1
| | - Hideki Masuda
- Department of Frontier Materials, Graduate School of Engineering, Nagoya Institute of Technology , Gokiso, Showa, Nagoya 466-8555, Japan
| |
Collapse
|
11
|
Bjornsson R, Neese F, Schrock RR, Einsle O, DeBeer S. The discovery of Mo(III) in FeMoco: reuniting enzyme and model chemistry. J Biol Inorg Chem 2014; 20:447-60. [PMID: 25549604 PMCID: PMC4334110 DOI: 10.1007/s00775-014-1230-6] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2014] [Accepted: 12/11/2014] [Indexed: 12/02/2022]
Abstract
Biological nitrogen fixation is enabled by molybdenum-dependent nitrogenase enzymes, which effect the reduction of dinitrogen to ammonia using an Fe7MoS9C active site, referred to as the iron molybdenum cofactor or FeMoco. In this mini-review, we summarize the current understanding of the molecular and electronic structure of FeMoco. The advances in our understanding of the active site structure are placed in context with the parallel evolution of synthetic model studies. The recent discovery of Mo(III) in the FeMoco active site is highlighted with an emphasis placed on the important role that model studies have played in this finding. In addition, the reactivities of synthetic models are discussed in terms of their relevance to the enzymatic system.
Collapse
Affiliation(s)
- Ragnar Bjornsson
- Max-Planck-Institut für Chemische Energiekonversion, Stiftstr. 34-36, 45470, Mülheim and Der Ruhr, Germany,
| | | | | | | | | |
Collapse
|
12
|
Cutsail III G, Stein BW, Subedi D, Smith JM, Kirk ML, Hoffman BM. EPR, ENDOR, and electronic structure studies of the Jahn-Teller distortion in an Fe(V) nitride. J Am Chem Soc 2014; 136:12323-36. [PMID: 25137531 PMCID: PMC4156863 DOI: 10.1021/ja505403j] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2014] [Indexed: 01/26/2023]
Abstract
The recently synthesized and isolated low-coordinate Fe(V) nitride complex has numerous implications as a model for high-oxidation states in biological and industrial systems. The trigonal [PhB((t)BuIm)3Fe(V)≡N](+) (where (PhB((t)BuIm)3(-) = phenyltris(3-tert-butylimidazol-2-ylidene)), (1) low-spin d(3) (S = 1/2) coordination compound is subject to a Jahn-Teller (JT) distortion of its doubly degenerate (2)E ground state. The electronic structure of this complex is analyzed by a combination of extended versions of the formal two-orbital pseudo Jahn-Teller (PJT) treatment and of quantum chemical computations of the PJT effect. The formal treatment is extended to incorporate mixing of the two e orbital doublets (30%) that results from a lowering of the idealized molecular symmetry from D3h to C3v through strong "doming" of the Fe-C3 core. Correspondingly we introduce novel DFT/CASSCF computational methods in the computation of electronic structure, which reveal a quadratic JT distortion and significant e-e mixing, thus reaching a new level of synergism between computational and formal treatments. Hyperfine and quadrupole tensors are obtained by pulsed 35 GHz ENDOR measurements for the (14/15)N-nitride and the (11)B axial ligands, and spectra are obtained from the imidazole-2-ylidene (13)C atoms that are not bound to Fe. Analysis of the nitride ENDOR tensors surprisingly reveals an essentially spherical nitride trianion bound to Fe, with negative spin density and minimal charge density anisotropy. The four-coordinate (11)B, as expected, exhibits negligible bonding to Fe. A detailed analysis of the frontier orbitals provided by the electronic structure calculations provides insight into the reactivity of 1: JT-induced symmetry lowering provides an orbital selection mechanism for proton or H atom transfer reactivity.
Collapse
Affiliation(s)
- George
E. Cutsail III
- Department
of Chemistry Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States
| | - Benjamin W. Stein
- Department
of Chemistry and Chemical Biology The University
of New Mexico, MSC03 2060, 300 Terrace St. NE, Albuquerque, New Mexico 87131-0001, United States
| | - Deepak Subedi
- Department
of Chemistry and Biochemistry MSC 3C, New
Mexico State University, 1175 North Horseshoe Drive, Las Cruces, New Mexico 88003, United States
| | - Jeremy M. Smith
- Department
of Chemistry and Biochemistry MSC 3C, New
Mexico State University, 1175 North Horseshoe Drive, Las Cruces, New Mexico 88003, United States
| | - Martin L. Kirk
- Department
of Chemistry and Chemical Biology The University
of New Mexico, MSC03 2060, 300 Terrace St. NE, Albuquerque, New Mexico 87131-0001, United States
| | - Brian M. Hoffman
- Department
of Chemistry and Biochemistry MSC 3C, New
Mexico State University, 1175 North Horseshoe Drive, Las Cruces, New Mexico 88003, United States
| |
Collapse
|
13
|
Ohki Y. Synthetic Analogues of the Active Sites of Nitrogenase and [NiFe] Hydrogenase. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2014. [DOI: 10.1246/bcsj.20130207] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Yasuhiro Ohki
- Department of Chemistry, Graduate School of Science, Nagoya University
| |
Collapse
|
14
|
Chiang KP, Bellows SM, Brennessel WW, Holland PL. Multimetallic Cooperativity in Activation of Dinitrogen at Iron-Potassium Sites. Chem Sci 2014; 5. [PMID: 24379972 DOI: 10.1039/c3sc52487f] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The reaction of soluble iron-oxygen-potassium assemblies with N2 gives insight into the mechanisms of multimetallic N2 coordination. We report a series of very electron-rich three-coordinate, β-diketiminate-supported iron(I) phenoxide complexes, which are metastable but have been characterized under Ar by both crystallography and solution methods. Both monomeric and dimeric Fe-OPh-K compounds have been characterized, and their iron environments are very similar in the solid and solution states. In the dimer, potassium ions hold together the phenoxide oxygens and aryl rings of the two halves, to give a flexible diiron core. The reactions of the monomeric and dimeric iron(I) compounds with N2 are surprisingly different: the mononuclear iron(I) complexes give no reaction with N2, but the dimeric Fe2K2 complex reacts rapidly to give a diiron-N2 product. Computational studies show that the key to the rapid N2 reaction of the dimer is the preorganization of the two iron atoms. Thus, cooperation between Fe (which weakens the N-N bond) and K (which orients the Fe atoms) can be used to create a low-energy pathway for N2 reactions.
Collapse
Affiliation(s)
- Karen P Chiang
- Department of Chemistry, University of Rochester, Rochester, New York 14627, USA
| | - Sarina M Bellows
- Department of Chemistry, University of Rochester, Rochester, New York 14627, USA
| | - William W Brennessel
- Department of Chemistry, University of Rochester, Rochester, New York 14627, USA
| | - Patrick L Holland
- Department of Chemistry, University of Rochester, Rochester, New York 14627, USA
| |
Collapse
|
15
|
Fe-N2/CO complexes that model a possible role for the interstitial C atom of FeMo-cofactor (FeMoco). Proc Natl Acad Sci U S A 2013; 110:15898-903. [PMID: 24043796 DOI: 10.1073/pnas.1310153110] [Citation(s) in RCA: 105] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We report here a series of four- and five-coordinate Fe model complexes that feature an axial tri(silyl)methyl ligand positioned trans to a substrate-binding site. This arrangement is used to crudely model a single-belt Fe site of the FeMo-cofactor that might bind N2 at a position trans to the interstitial C atom. Reduction of a trigonal pyramidal Fe(I) complex leads to uptake of N2 and subsequent functionalization furnishes an open-shell Fe-diazenido complex. A related series of five-coordinate Fe-CO complexes stable across three redox states is also described. Spectroscopic, crystallographic, and Density Functional Theory (DFT) studies of these complexes suggest that a decrease in the covalency of the Fe-C(alkyl) interaction occurs upon reduction and substrate binding. This leads to unusually long Fe-C(alkyl) bond distances that reflect an ionic Fe-C bond. The data presented are contextualized in support of a hypothesis wherein modulation of a belt Fe-C interaction in the FeMo-cofactor facilitates substrate binding and reduction.
Collapse
|
16
|
Stubbert BD, Vela J, Brennessel WW, Holland PL. A Sulfide-Bridged Diiron(II) Complex with a cis-N 2H 4Ligand. Z Anorg Allg Chem 2013; 639:1351-1355. [PMID: 24678131 PMCID: PMC3963182 DOI: 10.1002/zaac.201300163] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2013] [Accepted: 05/24/2013] [Indexed: 11/07/2022]
Abstract
A sulfide-bridged diiron(II) complex bearing a cis-N2H4 (hydrazine) ligand has been prepared by reaction of LFeII(μ-S)FeIIL (1; L = sterically encumbered βdiketiminate ligand) with 2 molar equivalents of N2H4. The metastable diiron(II) hydrazine complex LFeII(μ-S)(μH N-NH2)FeII (3) is formed, as shown by crystallography, and NMR, vibrational, and electronic absorption spectroscopies. Compound 3 has been crystallographically characterized as its DBU (1,8-diazabicyclo[5.4.0]undec-7$ene) adduct, which exhibits weak N-H···DBU hydrogen bonding. The synthetic process evolves roughly 2 equivalents of NH3. The cis-N2H4 bridge in 3 may be relevant to the structure and function of intermediates on the FeMoco of nitrogenase.
Collapse
Affiliation(s)
- Bryan D. Stubbert
- Department of Chemistry University of Rochester Rochester, NY, USA 14627
| | - Javier Vela
- Department of Chemistry University of Rochester Rochester, NY, USA 14627
| | | | - Patrick L. Holland
- Department of Chemistry University of Rochester Rochester, NY, USA 14627
| |
Collapse
|
17
|
|
18
|
Maekawa M, Daniliuc CG, Jones PG, Hohenberger J, Sutter J, Meyer K, Walter MD. Synthesis of [Cp′Fe(η3-BH4)] and Its Conversion to [Cp′FeBH2]3. Eur J Inorg Chem 2013. [DOI: 10.1002/ejic.201300168] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
|
19
|
Bartholomew ER, Volpe EC, Wolczanski PT, Lobkovsky EB, Cundari TR. Selective Extraction of N2 from Air by Diarylimine Iron Complexes. J Am Chem Soc 2013; 135:3511-27. [DOI: 10.1021/ja311021u] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Erika R. Bartholomew
- Department of Chemistry & Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853, United States
| | - Emily C. Volpe
- Department of Chemistry & Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853, United States
| | - Peter T. Wolczanski
- Department of Chemistry & Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853, United States
| | - Emil B. Lobkovsky
- Department of Chemistry & Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853, United States
| | - Thomas R. Cundari
- Department of Chemistry, Center for Advanced Scientific
Computing and Modeling (CASCaM), University of North Texas, Box 305070, Denton, Texas 76203-5070, United
States
| |
Collapse
|
20
|
Ohta S, Ohki Y, Hashimoto T, Cramer RE, Tatsumi K. A Nitrogenase Cluster Model [Fe8S6O] with an Oxygen Unsymmetrically Bridging Two Proto-Fe4S3 Cubes: Relevancy to the Substrate Binding Mode of the FeMo Cofactor. Inorg Chem 2012; 51:11217-9. [DOI: 10.1021/ic301348f] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Shun Ohta
- Department of Chemistry, Graduate School of Science, and Research Center for Meterials Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602,
Japan
| | - Yasuhiro Ohki
- Department of Chemistry, Graduate School of Science, and Research Center for Meterials Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602,
Japan
| | - Takayoshi Hashimoto
- Department of Chemistry, Graduate School of Science, and Research Center for Meterials Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602,
Japan
| | - Roger E. Cramer
- Department
of Chemistry, University of Hawaii, Honolulu, Hawaii
96822, United States
| | - Kazuyuki Tatsumi
- Department of Chemistry, Graduate School of Science, and Research Center for Meterials Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602,
Japan
| |
Collapse
|
21
|
Walter MD, White PS. Reactivity Studies on [Cp′FeI]2: Monomeric Amido, Phenoxo, and Alkyl Complexes. Inorg Chem 2012; 51:11860-72. [DOI: 10.1021/ic301770f] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- Marc D. Walter
- Institut für Anorganische
und Analytische Chemie, Technische Universität Braunschweig, Hagenring 30, 38106 Braunschweig, Germany
| | - Peter S. White
- Department of Chemistry, University of North Carolina at Chapel Hill, Chapel
Hill, North Carolina 27599-3290, United States
| |
Collapse
|
22
|
Suresh P, Sathyanarayana A, Prabusankar G, Hernandez O, Golhen S. The First Monomeric β-Diketiminate Stabilized Four-Coordinated Bismuth(III) Bistrifluoromethanesulfonate. Z Anorg Allg Chem 2012. [DOI: 10.1002/zaac.201100463] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
23
|
Lee Y, Kinney RA, Hoffman BM, Peters JC. A nonclassical dihydrogen adduct of S = ½ Fe(I). J Am Chem Soc 2011; 133:16366-9. [PMID: 21954981 DOI: 10.1021/ja207003m] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We have exploited the capacity of the "(SiP(iPr)(3))Fe(I)" scaffold to accommodate additional axial ligands and characterized the mononuclear S = ½ H(2) adduct complex (SiP(iPr)(3))Fe(I)(H(2)). EPR and ENDOR data, in the context of X-ray structural results, revealed that this complex provides a highly unusual example of an open-shell metal complex that binds dihydrogen as a ligand. The H(2) ligand at 2 K dynamically reorients within the ligand-binding pocket, tunneling among the energy minima created by strong interactions with the three Fe-P bonds.
Collapse
Affiliation(s)
- Yunho Lee
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA
| | | | | | | |
Collapse
|
24
|
Liu C, Cundari TR, Wilson AK. Reaction Mechanism of the Reverse Water–Gas Shift Reaction Using First-Row Middle Transition Metal Catalysts L′M (M = Fe, Mn, Co): A Computational Study. Inorg Chem 2011; 50:8782-9. [DOI: 10.1021/ic200602v] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Affiliation(s)
- Cong Liu
- Department of Chemistry and Center for Advanced Scientific Computing and Modeling (CASCaM), University of North Texas, Denton, Texas 76203-5070, United States
| | - Thomas R. Cundari
- Department of Chemistry and Center for Advanced Scientific Computing and Modeling (CASCaM), University of North Texas, Denton, Texas 76203-5070, United States
| | - Angela K. Wilson
- Department of Chemistry and Center for Advanced Scientific Computing and Modeling (CASCaM), University of North Texas, Denton, Texas 76203-5070, United States
| |
Collapse
|
25
|
Abstract
We report a unique class of dinitrogen complexes of iron featuring sulfur donors in the ancillary ligand. The ligands utilized are related to the recently studied tris(phosphino)silyl ligands (2-R(2)PC(6)H(4))(3)Si (R = Ph, iPr) but have one or two phosphine arms replaced with thioether donors. Depending on the number of phosphine arms replaced, both mononuclear and dinuclear iron complexes with dinitrogen are accessible. These complexes contribute to a desirable class of model complexes that possess both dinitrogen and sulfur ligands in the immediate iron coordination sphere.
Collapse
Affiliation(s)
- Ayumi Takaoka
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, USA
| | | | | |
Collapse
|
26
|
Field LD, Guest RW, Turner P. Mixed-valence dinitrogen-bridged Fe(0)/Fe(II) complex. Inorg Chem 2011; 49:9086-93. [PMID: 20815362 DOI: 10.1021/ic101646p] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The reactions of a dinitrogen-bridged Fe(II)/Fe(II) complex [(FeH(PP(3)))(2)(μ-N(2))](2+) (3) (PP(3) = P(CH(2)CH(2)PMe(2))(3)) with base were investigated using (15)N labeling techniques to enhance characterization. In the presence of base, 3 is initially deprotonated to the Fe(II)/Fe(0) dinitrogen-bridged complex [(FeH(PP(3)))(μ-N(2))(Fe(PP(3)))](+) (4) and then to the symmetrical Fe(0)/Fe(0) dinitrogen-bridged complex (Fe(PP(3)))(2)(μ-N(2)) (5). [(FeH(PP(3)))(μ-N(2))(Fe(PP(3)))](+) (4) exhibits unusual long-range (31)P-(31)P NMR coupling through the bridging dinitrogen ligand from the phosphines at the Fe(0) center and those at the Fe(II) center. Reaction of 4 with base under an atmosphere of argon resulted in the known dinitrogen Fe(0) complex Fe(N(2))(PP(3)) (6) and a solvent C-H activation product. Complexes 3, 4, and 5 were fully characterized by multinuclear NMR spectroscopy, and complexes 3 and 4 by X-ray crystallography.
Collapse
Affiliation(s)
- Leslie D Field
- School of Chemistry, The University of New South Wales, NSW 2052, Australia.
| | | | | |
Collapse
|
27
|
Fang M, Bates JE, Lorenz SE, Lee DS, Rego DB, Ziller JW, Furche F, Evans WJ. (N2)3− Radical Chemistry via Trivalent Lanthanide Salt/Alkali Metal Reduction of Dinitrogen: New Syntheses and Examples of (N2)2− and (N2)3− Complexes and Density Functional Theory Comparisons of Closed Shell Sc3+, Y3+, and Lu3+ versus 4f9 Dy3+. Inorg Chem 2011; 50:1459-69. [DOI: 10.1021/ic102016k] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- Ming Fang
- Department of Chemistry, University of California, Irvine, California 92697-2025, United States
| | - Jefferson E. Bates
- Department of Chemistry, University of California, Irvine, California 92697-2025, United States
| | - Sara E. Lorenz
- Department of Chemistry, University of California, Irvine, California 92697-2025, United States
| | - David S. Lee
- Department of Chemistry, University of California, Irvine, California 92697-2025, United States
| | - Daniel B. Rego
- Department of Chemistry, University of California, Irvine, California 92697-2025, United States
| | - Joseph W. Ziller
- Department of Chemistry, University of California, Irvine, California 92697-2025, United States
| | - Filipp Furche
- Department of Chemistry, University of California, Irvine, California 92697-2025, United States
| | - William J. Evans
- Department of Chemistry, University of California, Irvine, California 92697-2025, United States
| |
Collapse
|
28
|
Chang KC, Lu CF, Wang PY, Lu DY, Chen HZ, Kuo TS, Tsai YC. Ligand-controlled synthesis of vanadium(i) β-diketiminates and their catalysis in cyclotrimerization of alkynes. Dalton Trans 2011; 40:2324-31. [DOI: 10.1039/c0dt01061h] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
29
|
Chin JM, Schrock RR, Müller P. Synthesis of diamidopyrrolyl molybdenum complexes relevant to reduction of dinitrogen to ammonia. Inorg Chem 2010; 49:7904-16. [PMID: 20799738 DOI: 10.1021/ic100856n] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A potentially useful trianionic ligand for the reduction of dinitrogen catalytically by molybdenum complexes is one in which one of the arms in a [(RNCH(2)CH(2))(3)N](3-) ligand is replaced by a 2-mesitylpyrrolyl-alpha-methyl arm, that is, [(RNCH(2)CH(2))(2)NCH(2)(2-MesitylPyrrolyl)](3-) (R = C(6)F(5), 3,5-Me(2)C(6)H(3), or 3,5-t-Bu(2)C(6)H(3)). Compounds have been prepared that contain the ligand in which R = C(6)F(5) ([C(6)F(5)N)(2)Pyr](3-)); they include [(C(6)F(5)N)(2)Pyr]Mo(NMe(2)), [(C(6)F(5)N)(2)Pyr]MoCl, [(C(6)F(5)N)(2)Pyr]MoOTf, and [(C(6)F(5)N)(2)Pyr]MoN. Compounds that contain the ligand in which R = 3,5-t-Bu(2)C(6)H(3) ([Ar(t-Bu)N)(2)Pyr](3-)) include {[(Ar(t-Bu)N)(2)Pyr]Mo(N(2))}Na(15-crown-5), {[(Ar(t-Bu)N)(2)Pyr]Mo(N(2))}[NBu(4)], [(Ar(t-Bu)N)(2)Pyr]Mo(N(2)) (nu(NN) = 2012 cm(-1) in C(6)D(6)), {[(Ar(t-Bu)N)(2)Pyr]Mo(NH(3))}BPh(4), and [(Ar(t-Bu)N)(2)Pyr]Mo(CO). X-ray studies are reported for [(C(6)F(5)N)(2)Pyr]Mo(NMe(2)), [(C(6)F(5)N)(2)Pyr]MoCl, and [(Ar(t-Bu)N)(2)Pyr]MoN. The [(Ar(t-Bu)N)(2)Pyr]Mo(N(2))(0/-) reversible couple is found at -1.96 V (in PhF versus Cp(2)Fe(+/0)), but the [(Ar(t-Bu)N)(2)Pyr]Mo(N(2))(+/0) couple is irreversible. Reduction of {[(Ar(t-Bu)N)(2)Pyr]Mo(NH(3))}BPh(4) under Ar at approximately -1.68 V at a scan rate of 900 mV/s is not reversible. Ammonia in [(Ar(t-Bu)N)(2)Pyr]Mo(NH(3)) can be substituted for dinitrogen in about 2 h if 10 equiv of BPh(3) are present to trap the ammonia that is released. [(Ar(t-Bu)N)(2)Pyr]Mo-N=NH is a key intermediate in the proposed catalytic reduction of dinitrogen that could not be prepared. Dinitrogen exchange studies in [(Ar(t-Bu)N)(2)Pyr]Mo(N(2)) suggest that steric hindrance by the ligand may be insufficient to protect decomposition of [(Ar(t-Bu)N)(2)Pyr]Mo-N=NH through a variety of pathways. Three attempts to reduce dinitrogen catalytically with [(Ar(t-Bu)N)(2)Pyr]Mo(N) as a "catalyst" yielded an average of 1.02 +/- 0.12 equiv of NH(3).
Collapse
Affiliation(s)
- J M Chin
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | | | | |
Collapse
|
30
|
|
31
|
Liu C, Munjanja L, Cundari TR, Wilson AK. Theoretical Studies on the Catalysis of the Reverse Water−Gas Shift Reaction Using First-Row Transition Metal β-Diketiminato Complexes. J Phys Chem A 2010; 114:6207-16. [DOI: 10.1021/jp911616y] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Affiliation(s)
- Cong Liu
- Department of Chemistry and Center for Advanced Scientific Computing and Modeling (CASCaM), University of North Texas, Denton, Texas 76203-5070
| | - Lloyd Munjanja
- Department of Chemistry and Center for Advanced Scientific Computing and Modeling (CASCaM), University of North Texas, Denton, Texas 76203-5070
| | - Thomas R. Cundari
- Department of Chemistry and Center for Advanced Scientific Computing and Modeling (CASCaM), University of North Texas, Denton, Texas 76203-5070
| | - Angela K. Wilson
- Department of Chemistry and Center for Advanced Scientific Computing and Modeling (CASCaM), University of North Texas, Denton, Texas 76203-5070
| |
Collapse
|
32
|
Hazari N. Homogeneous iron complexes for the conversion of dinitrogen into ammonia and hydrazine. Chem Soc Rev 2010; 39:4044-56. [DOI: 10.1039/b919680n] [Citation(s) in RCA: 207] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
33
|
Phillips AD, Zava O, Scopelitti R, Nazarov AA, Dyson PJ. Rational Design of Highly Cytotoxic η6-Arene β-Diketiminato−Ruthenium Complexes. Organometallics 2009. [DOI: 10.1021/om900991b] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Andrew D. Phillips
- School of Chemistry and Chemical Biology, University College Dublin, Belfield, Dublin 4, Ireland
- Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Olivier Zava
- Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Rosario Scopelitti
- Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Alexey A. Nazarov
- Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| | - Paul J. Dyson
- Institut des Sciences et Ingénierie Chimiques, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
| |
Collapse
|
34
|
Whited MT, Mankad NP, Lee Y, Oblad PF, Peters JC. Dinitrogen Complexes Supported by Tris(phosphino)silyl Ligands. Inorg Chem 2009; 48:2507-17. [DOI: 10.1021/ic801855y] [Citation(s) in RCA: 124] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Matthew T. Whited
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Neal P. Mankad
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Yunho Lee
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Paul F. Oblad
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Jonas C. Peters
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| |
Collapse
|
35
|
Wang L, Chambron JC, Espinosa E. Versatility and dynamics of the copper(i) coordination sphere in sterically hindering tris(pyrazolyl)methane-incorporating macrobicycles. NEW J CHEM 2009. [DOI: 10.1039/b816275a] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
36
|
Rose RP, Jones C, Schulten C, Aldridge S, Stasch A. Synthesis and Characterization of Amidinate-Iron(I) Complexes: Analogies with β-Diketiminate Chemistry. Chemistry 2008; 14:8477-80. [PMID: 18698573 DOI: 10.1002/chem.200801071] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Richard P Rose
- School of Chemistry, Monash University, Melbourne, Victoria, Australia
| | | | | | | | | |
Collapse
|
37
|
Holland PL. Electronic structure and reactivity of three-coordinate iron complexes. Acc Chem Res 2008; 41:905-14. [PMID: 18646779 DOI: 10.1021/ar700267b] [Citation(s) in RCA: 241] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
[Reaction: see text]. The identity and oxidation state of the metal in a coordination compound are typically thought to be the most important determinants of its reactivity. However, the coordination number (the number of bonds to the metal) can be equally influential. This Account describes iron complexes with a coordination number of only three, which differ greatly from iron complexes with octahedral (six-coordinate) geometries with respect to their magnetism, electronic structure, preference for ligands, and reactivity. Three-coordinate complexes with a trigonal-planar geometry are accessible using bulky, anionic, bidentate ligands (beta-diketiminates) that steer a monodentate ligand into the plane of their two nitrogen donors. This strategy has led to a variety of three-coordinate iron complexes in which iron is in the +1, +2, and +3 oxidation states. Systematic studies on the electronic structures of these complexes have been useful in interpreting their properties. The iron ions are generally high spin, with singly occupied orbitals available for pi interactions with ligands. Trends in sigma-bonding show that iron(II) complexes favor electronegative ligands (O, N donors) over electropositive ligands (hydride). The combination of electrostatic sigma-bonding and the availability of pi-interactions stabilizes iron(II) fluoride and oxo complexes. The same factors destabilize iron(II) hydride complexes, which are reactive enough to add the hydrogen atom to unsaturated organic molecules and to take part in radical reactions. Iron(I) complexes use strong pi-backbonding to transfer charge from iron into coordinated alkynes and N 2, whereas iron(III) accepts charge from a pi-donating imido ligand. Though the imidoiron(III) complex is stabilized by pi-bonding in the trigonal-planar geometry, addition of pyridine as a fourth donor weakens the pi-bonding, which enables abstraction of H atoms from hydrocarbons. The unusual bonding and reactivity patterns of three-coordinate iron compounds may lead to new catalysts for oxidation and reduction reactions and may be used by nature in transient intermediates of nitrogenase enzymes.
Collapse
Affiliation(s)
- Patrick L. Holland
- Department of Chemistry, University of Rochester, Rochester, New York 14627
| |
Collapse
|
38
|
Yu Y, Sadique AR, Smith JM, Dugan TR, Cowley RE, Brennessel WW, Flaschenriem CJ, Bill E, Cundari TR, Holland PL. The reactivity patterns of low-coordinate iron-hydride complexes. J Am Chem Soc 2008; 130:6624-38. [PMID: 18444648 PMCID: PMC2474859 DOI: 10.1021/ja710669w] [Citation(s) in RCA: 163] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
We report a survey of the reactivity of the first isolable iron-hydride complexes with a coordination number less than 5. The high-spin iron(II) complexes [(beta-diketiminate)Fe(mu-H)] 2 react rapidly with representative cyanide, isocyanide, alkyne, N 2, alkene, diazene, azide, CO 2, carbodiimide, and Brønsted acid containing substrates. The reaction outcomes fall into three categories: (1) addition of Fe-H across a multiple bond of the substrate, (2) reductive elimination of H 2 to form iron(I) products, and (3) protonation of the hydride to form iron(II) products. The products include imide, isocyanide, vinyl, alkyl, azide, triazenido, benzo[ c]cinnoline, amidinate, formate, and hydroxo complexes. These results expand the range of known bond transformations at iron complexes. Additionally, they give insight into the elementary transformations that may be possible at the iron-molybdenum cofactor of nitrogenases, which may have hydride ligands on high-spin, low-coordinate metal atoms.
Collapse
Affiliation(s)
- Ying Yu
- Department of Chemistry, University of Rochester, Rochester, New York, 14627
| | - Azwana R. Sadique
- Department of Chemistry, University of Rochester, Rochester, New York, 14627
| | - Jeremy M. Smith
- Department of Chemistry, University of Rochester, Rochester, New York, 14627
| | - Thomas R. Dugan
- Department of Chemistry, University of Rochester, Rochester, New York, 14627
| | - Ryan E. Cowley
- Department of Chemistry, University of Rochester, Rochester, New York, 14627
| | | | | | - Eckhard Bill
- Max-Planck-Institut für Bioanorganische Chemie, D-45470 Mülheim an der Ruhr, Germany
| | - Thomas R. Cundari
- Department of Chemistry and Center for Advanced Scientific Computing and Modeling (CASCaM), University of North Texas, Denton, Texas, 76203
| | - Patrick L. Holland
- Department of Chemistry, University of Rochester, Rochester, New York, 14627
| |
Collapse
|
39
|
Berben LA, Kozimor SA. Dinitrogen and Acetylide Complexes of Low-Valent Chromium. Inorg Chem 2008; 47:4639-47. [DOI: 10.1021/ic702275g] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Louise A. Berben
- Department of Chemistry, University of California, Berkeley, California 94720–1460
| | - Stosh A. Kozimor
- Department of Chemistry, University of California, Berkeley, California 94720–1460
| |
Collapse
|
40
|
Lees NS, McNaughton RL, Gregory WV, Holland PL, Hoffman BM. ENDOR Characterization of a Synthetic Diiron Hydrazido Complex as a Model for Nitrogenase Intermediates. J Am Chem Soc 2007; 130:546-55. [DOI: 10.1021/ja073934x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Nicholas S. Lees
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208 and Department of Chemistry, University of Rochester, RC Box 270216, Rochester, New York 14627-0216
| | - Rebecca L. McNaughton
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208 and Department of Chemistry, University of Rochester, RC Box 270216, Rochester, New York 14627-0216
| | - Wilda Vargas Gregory
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208 and Department of Chemistry, University of Rochester, RC Box 270216, Rochester, New York 14627-0216
| | - Patrick L. Holland
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208 and Department of Chemistry, University of Rochester, RC Box 270216, Rochester, New York 14627-0216
| | - Brian M. Hoffman
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208 and Department of Chemistry, University of Rochester, RC Box 270216, Rochester, New York 14627-0216
| |
Collapse
|
41
|
Kozlowski PM, Shiota Y, Gomita S, Seino H, Mizobe Y, Yoshizawa K. DFT Analysis of Cubane-Type FeIr3S4Clusters. Dinitrogen Binding and Activation at the Tetrahedral Fe Site. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2007. [DOI: 10.1246/bcsj.80.2323] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
|
42
|
Studt F, Tuczek F. Theoretical, spectroscopic, and mechanistic studies on transition-metal dinitrogen complexes: implications to reactivity and relevance to the nitrogenase problem. J Comput Chem 2007; 27:1278-91. [PMID: 16786542 DOI: 10.1002/jcc.20413] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Dinitrogen complexes of transition metals exhibit different binding geometries of N2 (end-on terminal, end-on bridging, side-on bridging, side-on end-on bridging), which are investigated by spectroscopy and DFT calculations, analyzing their electronic structure and reactivity. For comparison, a bis(mu-nitrido) complex, where the N--N bond has been split, has been studied as well. Most of these systems are highly covalent, and have strong metal-nitrogen bonds. In the present review, particular emphasis is put on a consideration of the activation of the coordinated dinitrogen ligand, making it susceptible to protonation, reactions with electrophiles or cleavage. In this context, theoretical, structural, and spectroscopic data giving informations on the amount of charge on the N2 unit are presented. The orbital interactions leading to a charge transfer from the metals to the dinitrogen ligand and the charge distribution within the coordinated N2 group are analyzed. Correlations between the binding mode and the observed reactivity of N2 are discussed.
Collapse
Affiliation(s)
- Felix Studt
- Institut für Anorganische Chemie, Christian-Albrechts-Universität Kiel, Otto Hahn Platz 6/7, 24098 Kiel, Germany
| | | |
Collapse
|
43
|
Stoian SA, Vela J, Smith JM, Sadique AR, Holland PL, Münck E, Bominaar EL. Mössbauer and computational study of an N2-bridged diiron diketiminate complex: parallel alignment of the iron spins by direct antiferromagnetic exchange with activated dinitrogen. J Am Chem Soc 2007; 128:10181-92. [PMID: 16881648 DOI: 10.1021/ja062051n] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
This work reports Mössbauer and DFT studies of the diiron-N2 complex LMeFeNNFeLMe (L = beta-diketiminate), 1a. Complex 1a, formally diiron(I), has a system spin S = 3 with an isolated MS = +/-3 quasi-doublet as a ground state; the MS = +/-2 doublet is >100 cm-1 higher in energy. Complex 1a exhibits at 4.2 K a large, positive magnetic hyperfine field, Bint = +68.1 T, and an effective g value of 16 +/- 2 along the easy magnetization axis of the ground doublet; this value is significantly larger than the spin-only value (g = 12). These results have been rationalized by DFT calculations, which show that each Fe site donates significant electron density into the pi* orbitals of dinitrogen, resulting in a configuration best described as two high-spin FeII (Sa = Sb = 2) bridged by triplet N22- (Sc = 1). In this description the minority spin electron of each iron is accommodated by two nonbonding, closely spaced 3d orbitals, z2 and yz (z is perpendicular to the diketiminate planes, x is along the Fe...Fe vector). Spin-orbit coupling between these orbital states generates a large unquenched orbital momentum along the iron-iron vector. The S = 3 ground state of 1a results from strong antiferromagnetic direct exchange couplings of the Fe spins (Sa = Sb = 2) to the N22- spin (Sc = 1) and can be formulated as ((Sa,Sb)Sab = 4, Sc = 1), S = 3>; H = J(Sa + Sb).Sc with J approximately 3500 cm-1.
Collapse
Affiliation(s)
- Sebastian A Stoian
- Department of Chemistry, Carnegie Mellon University, 4400 Fifth Avenue, Pittsburgh, Pennsylvania 15213, USA
| | | | | | | | | | | | | |
Collapse
|
44
|
Sadique AR, Gregory EA, Brennessel WW, Holland PL. Mechanistic insight into N=N cleavage by a low-coordinate iron(II) hydride complex. J Am Chem Soc 2007; 129:8112-21. [PMID: 17564444 PMCID: PMC2548314 DOI: 10.1021/ja069199r] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The reaction pathways of high-spin iron hydride complexes are relevant to the mechanism of N2 reduction by nitrogenase, which has been postulated to involve paramagnetic iron-hydride species. However, almost all known iron hydrides are low-spin, diamagnetic Fe(II) compounds. We have demonstrated that the first high-spin iron hydride complex, LtBuFeH (LtBu = bulky beta-diketiminate), reacts with PhN=NPh to completely cleave the N-N double bond, giving LtBuFeNHPh. Here, we disclose a series of experiments that elucidate the mechanism of this reaction. Crossover and kinetic experiments rule out common nonradical mechanisms, and support a radical chain mechanism mediated by iron(I) species including a rare eta2-azobenzene complex. Therefore, this high-spin iron(II) hydride can break N-N bonds through both nonradical and radical insertion mechanisms, a special feature that enables novel reactivity.
Collapse
Affiliation(s)
- Azwana R. Sadique
- Department of Chemistry, University of Rochester, Rochester, New York 14627,
| | | | | | - Patrick L. Holland
- Department of Chemistry, University of Rochester, Rochester, New York 14627,
| |
Collapse
|
45
|
Vela J, Cirera J, Smith JM, Lachicotte RJ, Flaschenriem CJ, Alvarez S, Holland PL. Quantitative geometric descriptions of the belt iron atoms of the iron-molybdenum cofactor of nitrogenase and synthetic iron(II) model complexes. Inorg Chem 2007; 46:60-71. [PMID: 17198413 PMCID: PMC2676240 DOI: 10.1021/ic0609148] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Six of the seven iron atoms in the iron-molybdenum cofactor of nitrogenase display an unusual geometry, which is distorted from the tetrahedral geometry that is most common in iron-sulfur clusters. This distortion pulls the iron along one C3 axis of the tetrahedron toward a trigonal pyramid. The trigonal pyramidal coordination geometry is rare in four-coordinate transition metal complexes. In order to document this geometry in a systematic fashion in iron(II) chemistry, we have synthesized a range of four-coordinate iron(II) complexes that vary from tetrahedral to trigonal pyramidal. Continuous shape measures are used for a quantitative comparison of the stereochemistry of the Fe atoms in the iron-molybdenum cofactor with those of the presently and previously reported model complexes, as well as with those in polynuclear iron-sulfur compounds. This understanding of the iron coordination geometry is expected to assist in the design of synthetic analogues for intermediates in the nitrogenase catalytic cycle.
Collapse
Affiliation(s)
- Javier Vela
- Department of Chemistry, University of Rochester, Rochester, New York 14627, USA
| | | | | | | | | | | | | |
Collapse
|
46
|
Vela J, Zhu L, Flaschenriem CJ, Brennessel WW, Lachicotte RJ, Holland PL. Macrocyclic Binucleating β-Diketiminate Ligands and their Lithium, Aluminum, and Zinc Complexes. Organometallics 2007; 26:3416-3423. [PMID: 19132137 PMCID: PMC2614679 DOI: 10.1021/om0700258] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The incorporation of rigid aromatic linkers into β-diketiminate ligands creates a binucleating scaffold that holds two metals near each other. This paper discloses the synthesis, characterization, and reactivity of mBin(2-), which has a meta-substituted xylylene spacer, and pBin(2-), which has a para-substituted xylylene spacer. Lithium, aluminum, and zinc complexes of each ligand are isolated, and in some cases are characterized by X-ray crystallography. The lithium complexes are coordinated to solvent-derived THF ligands, while the zinc and aluminum complexes have alkyl ligands. Complexes of the mBin(2-) ligand have an anti conformation in which the metals are on opposite sides of the macrocycle, while pBin(2-) complexes prefer a syn conformation. The (1)H NMR spectra of the complexes demonstrate that the conformations rapidly interconvert in the lithium complexes, and less rapidly in the zinc and aluminum complexes.
Collapse
Affiliation(s)
- Javier Vela
- Department of Chemistry, University of Rochester, Rochester, NY, 14627
| | - Liwei Zhu
- Department of Chemistry, University of Rochester, Rochester, NY, 14627
| | | | | | | | | |
Collapse
|
47
|
Reductive C–N bond cleavage of the NCCCN β-diketiminate backbone: A direct approach to azabutadienyl and alkylidene-anilide scaffolds. Inorganica Chim Acta 2007. [DOI: 10.1016/j.ica.2006.07.045] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
48
|
Weare WW, Schrock RR, Hock AS, Müller P. Synthesis of molybdenum complexes that contain "hybrid" triamidoamine ligands, [(hexaisopropylterphenyl-NCH2CH2)2NCH2CH2N-aryl]3-, and studies relevant to catalytic reduction of dinitrogen. Inorg Chem 2006; 45:9185-96. [PMID: 17083216 PMCID: PMC2597297 DOI: 10.1021/ic0613457] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In the Buchwald-Hartwig reaction between HIPTBr (HIPT = 3,5-(2,4,6-i-Pr3C6H2)2C6H3 = hexaisopropylterphenyl) and (H2NCH2CH2)3N, it is possible to obtain a 65% isolated yield of (HIPTNHCH2CH2)2NCH2CH2NH2. A second coupling then can be carried out to yield a variety of "hybrid" ligands, (HIPTNHCH2CH2)2NCH2CH2NHAr, where Ar = 3,5-Me2C6H3, 3,5-(CF3)2C6H3, 3,5-(MeO)2C6H3, 3,5-Me2NC5H3, 3,5-Ph2NC5H3, 2,4,6-i-Pr3C6H2, or 2,4,6-Me3C6H2. The hybrid ligands may be attached to Mo to yield [hybrid]MoCl species. From the monochloride species, a variety of other species such as [hybrid]MoN, {[hybrid]MoN2}Na, and {[hybrid]Mo(NH3)}+ can be prepared. [Hybrid]MoN2 species were prepared through oxidation of {[hybrid]MoN2}Na species with ZnCl2, but they could not be isolated. [Hybrid]Mo=N-NH species could be observed as a consequence of the protonation of {[hybrid]MoN2}- species, but they too could not be isolated as a consequence of a facile decomposition to yield dihydrogen and [hybrid]MoN2 species. Attempts to reduce dinitrogen catalytically led to little or no ammonia being formed from dinitrogen. The fact that no ammonia was formed from dinitrogen in the case of Ar = 3,5-Me2C6H3, 3,5-(CF3)2C6H3, or 3,5-(MeO)2C6H3 could be attributed to a rapid decomposition of intermediate [hybrid]Mo=N-NH species in the catalytic reaction, a decomposition that was shown in separate studies to be accelerated dramatically by 2,6-lutidine, the conjugate base of the acid employed in the attempted catalytic reduction. X-ray structures of [(HIPTNHCH2CH2)2NCH2CH2N{3,5-(CF3)2C6H3}]MoCl and [(HIPTNHCH2CH2)2NCH2CH2N(3,5-Me2C6H3)]MoN2}Na(THF)2 are reported.
Collapse
Affiliation(s)
- Walter W Weare
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307, USA
| | | | | | | |
Collapse
|
49
|
Lesikar LA, Richards AF. Synthesis and characterization of β-diketiminato complexes of antimony (III) halides. J Organomet Chem 2006. [DOI: 10.1016/j.jorganchem.2006.06.036] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
|
50
|
Hebden TJ, Brennessel WW, Flaschenriem CJ, Holland PL. A dinucleating ligand related to the beta-diketiminates. Dalton Trans 2006:3855-7. [PMID: 16896444 PMCID: PMC1586103 DOI: 10.1039/b607440e] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A new ligand conceptually creates two sites reminiscent of beta-diketiminates, and upon deprotonation the salts exist in oligomeric forms with potassium ions linking multiple ligands.
Collapse
Affiliation(s)
- Travis J. Hebden
- Department of Chemistry, University of Rochester, Rochester, NY 14627, USA. E-mail:
| | | | | | - Patrick L. Holland
- Department of Chemistry, University of Rochester, Rochester, NY 14627, USA. E-mail:
| |
Collapse
|