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Zhang X, Jiang X, Zhao Q, Li Y, Feng L, Ye S, Tung CH, Wang W. Synthesis and Characterization of Bridging-Diazene Diiron Half-Sandwich Complexes: The Role of Sulfur Hydrogen Bonding. Inorg Chem 2024; 63:14040-14049. [PMID: 39007501 DOI: 10.1021/acs.inorgchem.4c01783] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/16/2024]
Abstract
We report two bridging-diazene diiron complexes [Cp*Fe(8-quinolinethiolate)]2(μ-N2H2) (1-N2H2) and [Cp*Fe(1,2-Cy2PC6H4S)]2(μ-N2H2) (2-N2H2), synthesized by the reaction of hydrazine with the corresponding thiolate-based iron half-sandwich complex, [Cp*Fe(8-quinolinethiolate)]2 (1) and Cp*Fe(1,2-Cy2PC6H4S) (2). Crystallographic analysis reveals that the thiolate sites in 1-N2H2 and 2-N2H2 can engage in N-H···S hydrogen bonding with the diazene protons. 1-N2H2 is thermally stable in both solid and solution states, allowing for one-electron oxidation to afford a cationic diazene radical complex [1-N2H2]+ at room temperature. In contrast, 2-N2H2 tends to undergo N2H2/N2 transformation, leading to the formation of a Fe(III)-H species by the loss of N2. In addition to stabilizing HN=NH species through the hydrogen bonding, the thiolate-based ligands also seem to facilitate proton-coupled electron transfer, thereby promoting N-H cleavage.
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Affiliation(s)
- Xin Zhang
- School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, China
| | - Xuebin Jiang
- State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Qiuting Zhao
- College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Yongxian Li
- College of Chemistry, Beijing Normal University, Beijing 100875, China
| | - Lei Feng
- School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, China
| | - Shengfa Ye
- State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China
| | - Chen-Ho Tung
- School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, China
| | - Wenguang Wang
- School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, China
- College of Chemistry, Beijing Normal University, Beijing 100875, China
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Hooper RX, Wertz AE, Shafaat HS, Holland PL. Evaluating Diazene to N 2 Interconversion at Iron-Sulfur Complexes. Chemistry 2024; 30:e202304072. [PMID: 38376370 PMCID: PMC11045311 DOI: 10.1002/chem.202304072] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2023] [Revised: 02/19/2024] [Accepted: 02/20/2024] [Indexed: 02/21/2024]
Abstract
Biological N2 reduction occurs at sulfur-rich multiiron sites, and an interesting potential pathway is concerted double reduction/ protonation of bridging N2 through PCET. Here, we test the feasibility of using synthetic sulfur-supported diiron complexes to mimic this pathway. Oxidative proton transfer from μ-η1 : η1-diazene (HN=NH) is the microscopic reverse of the proposed N2 fixation pathway, revealing the energetics of the process. Previously, Sellmann assigned the purple metastable product from two-electron oxidation of [{Fe2+(PPr3)L1}2(μ-η1 : η1-N2H2)] (L1=tetradentate SSSS ligand) at -78 °C as [{Fe2+(PPr3)L1}2(μ-η1 : η1-N2)]2+, which would come from double PCET from diazene to sulfur atoms of the supporting ligands. Using resonance Raman, Mössbauer, NMR, and EPR spectroscopies in conjunction with DFT calculations, we show that the product is not an N2 complex. Instead, the data are most consistent with the spectroscopically observed species being the mononuclear iron(III) diazene complex [{Fe(PPr3)L1}(η2-N2H2)]+. Calculations indicate that the proposed double PCET has a barrier that is too high for proton transfer at the reaction temperature. Also, PCET from the bridging diazene is highly exergonic as a result of the high Fe3+/2+ redox potential, indicating that the reverse N2 protonation would be too endergonic to proceed. This system establishes the "ground rules" for designing reversible N2/N2H2 interconversion through PCET, such as tuning the redox potentials of the metal sites.
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Affiliation(s)
- Reagan X Hooper
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, CT-06511
| | - Ashlee E Wertz
- Department of Chemistry and Biochemistry, The Ohio State University, 100 W 18th Ave, Columbus, OH-43210
| | - Hannah S Shafaat
- Department of Chemistry and Biochemistry, The Ohio State University, 100 W 18th Ave, Columbus, OH-43210
- Department of Chemistry and Biochemistry, University of California, Los Angeles, 607 Charles E. Young Drive East, Los Angeles, CA-90095
| | - Patrick L Holland
- Department of Chemistry, Yale University, 225 Prospect Street, New Haven, CT-06511
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Gardner EJ, Marguet SC, Cobb CR, Pham DM, Beringer JAM, Bertke JA, Shafaat HS, Warren TH. Uncovering Redox Non-innocent Hydrogen-Bonding in Cu(I)-Diazene Complexes. J Am Chem Soc 2021; 143:15960-15974. [PMID: 34546737 DOI: 10.1021/jacs.1c04108] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The life-sustaining reduction of N2 to NH3 is thermoneutral yet kinetically challenged by high-energy intermediates such as N2H2. Exploring intramolecular H-bonding as a potential strategy to stabilize diazene intermediates, we employ a series of [xHetTpCu]2(μ-N2H2) complexes that exhibit H-bonding between pendant aromatic N-heterocycles (xHet) such as pyridine and a bridging trans-N2H2 ligand at copper(I) centers. X-ray crystallography and IR spectroscopy clearly reveal H-bonding in [pyMeTpCu]2(μ-N2H2) while low-temperature 1H NMR studies coupled with DFT analysis reveals a dynamic equilibrium between two closely related, symmetric H-bonded structural motifs. Importantly, the xHet pendant negligibly influences the electronic structure of xHetTpCuI centers in xHetTpCu(CNAr2,6-Me2) complexes that lack H-bonding as judged by nearly indistinguishable ν(CN) frequencies (2113-2117 cm-1). Nonetheless, H-bonding in the corresponding [xHetTpCu]2(μ-N2H2) complexes results in marked changes in ν(NN) (1398-1419 cm-1) revealed through resonance Raman studies. Due to the closely matched N-H BDEs of N2H2 and the pyH0 cation radical, the aromatic N-heterocyclic pendants may encourage partial H-atom transfer (HAT) from N2H2 to xHet through redox-non-innocent H-bonding in [xHetTpCu]2(μ-N2H2). DFT studies reveal modest thermodynamic barriers for concerted transfer of both H-atoms of coordinated N2H2 to the xHet pendants to generate tautomeric [xHetHTpCu]2(μ-N2) complexes, identifying metal-assisted concerted dual HAT as a thermodynamically favorable pathway for N2/N2H2 interconversion.
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Affiliation(s)
- Evan J Gardner
- Department of Chemistry, Georgetown University, Box 51277-1227, Washington, D.C. 20057, United States
| | - Sean C Marguet
- The Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, United States
| | - Caitlyn R Cobb
- Department of Chemistry, Georgetown University, Box 51277-1227, Washington, D.C. 20057, United States
| | - Dominic M Pham
- Department of Chemistry, Georgetown University, Box 51277-1227, Washington, D.C. 20057, United States
| | - Josalyne A M Beringer
- Department of Chemistry, Georgetown University, Box 51277-1227, Washington, D.C. 20057, United States
| | - Jeffery A Bertke
- Department of Chemistry, Georgetown University, Box 51277-1227, Washington, D.C. 20057, United States
| | - Hannah S Shafaat
- The Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, United States
| | - Timothy H Warren
- Department of Chemistry, Georgetown University, Box 51277-1227, Washington, D.C. 20057, United States
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4
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Nurdin L, Yang Y, Neate PGN, Piers WE, Maron L, Neidig ML, Lin JB, Gelfand BS. Activation of ammonia and hydrazine by electron rich Fe(ii) complexes supported by a dianionic pentadentate ligand platform through a common terminal Fe(iii) amido intermediate. Chem Sci 2020; 12:2231-2241. [PMID: 34163989 PMCID: PMC8179247 DOI: 10.1039/d0sc06466a] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
We report the use of electron rich iron complexes supported by a dianionic diborate pentadentate ligand system, B2Pz4Py, for the coordination and activation of ammonia (NH3) and hydrazine (NH2NH2). For ammonia, coordination to neutral (B2Pz4Py)Fe(ii) or cationic [(B2Pz4Py)Fe(iii)]+ platforms leads to well characterized ammine complexes from which hydrogen atoms or protons can be removed to generate, fleetingly, a proposed (B2Pz4Py)Fe(iii)–NH2 complex (3Ar-NH2). DFT computations suggest a high degree of spin density on the amido ligand, giving it significant aminyl radical character. It rapidly traps the H atom abstracting agent 2,4,6-tri-tert-butylphenoxy radical (ArO˙) to form a C–N bond in a fully characterized product (2Ar), or scavenges hydrogen atoms to return to the ammonia complex (B2Pz4Py)Fe(ii)–NH3 (1Ar-NH3). Interestingly, when (B2Pz4Py)Fe(ii) is reacted with NH2NH2, a hydrazine bridged dimer, (B2Pz4Py)Fe(ii)–NH2NH2–Fe(ii)(B2Pz4Py) ((1Ar)2-NH2NH2), is observed at −78 °C and converts to a fully characterized bridging diazene complex, 4Ar, along with ammonia adduct 1Ar-NH3 as it is allowed to warm to room temperature. Experimental and computational evidence is presented to suggest that (B2Pz4Py)Fe(ii) induces reductive cleavage of the N–N bond in hydrazine to produce the Fe(iii)–NH2 complex 3Ar-NH2, which abstracts H˙ atoms from (1Ar)2-NH2NH2 to generate the observed products. All of these transformations are relevant to proposed steps in the ammonia oxidation reaction, an important process for the use of nitrogen-based fuels enabled by abundant first row transition metals. Synopsis: a highly reactive Fe(iii)–NH2 complex is generated via activation of ammonia or hydrazine in reactions of relevance to fundamental steps in ammonia oxidation processes mediated by an abundant, first row transition metal.![]()
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Affiliation(s)
- Lucie Nurdin
- Department of Chemistry, University of Calgary 2500 University Drive NW Calgary Alberta T2N 1N4 Canada
| | - Yan Yang
- LPCNO, Université de Toulouse, INSA, UPS Toulouse France
| | - Peter G N Neate
- Department of Chemistry, University of Rochester Rochester New York 14627 USA
| | - Warren E Piers
- Department of Chemistry, University of Calgary 2500 University Drive NW Calgary Alberta T2N 1N4 Canada
| | - Laurent Maron
- LPCNO, Université de Toulouse, INSA, UPS Toulouse France
| | - Michael L Neidig
- Department of Chemistry, University of Rochester Rochester New York 14627 USA
| | - Jian-Bin Lin
- Department of Chemistry, University of Calgary 2500 University Drive NW Calgary Alberta T2N 1N4 Canada
| | - Benjamin S Gelfand
- Department of Chemistry, University of Calgary 2500 University Drive NW Calgary Alberta T2N 1N4 Canada
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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
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Affiliation(s)
- Ionel Haiduc
- Facultatea de Chimie, Universitatea Babeş-Bolyai, Cluj-Napoca, Romania
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7
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Tanabe Y, Nishibayashi Y. Catalytic Dinitrogen Fixation to Form Ammonia at Ambient Reaction Conditions Using Transition Metal-Dinitrogen Complexes. CHEM REC 2016; 16:1549-77. [DOI: 10.1002/tcr.201600025] [Citation(s) in RCA: 77] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Indexed: 01/23/2023]
Affiliation(s)
- Yoshiaki Tanabe
- Department of Systems Innovation, School of Engineering; The University of Tokyo; Hongo, Bunkyo-ku Tokyo 113-8656 Japan
| | - Yoshiaki Nishibayashi
- Department of Systems Innovation, School of Engineering; The University of Tokyo; Hongo, Bunkyo-ku Tokyo 113-8656 Japan
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8
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Luo L, Chen S, Luo Y, Qu J. A theoretical study on single-electron reduction of a thiolate-bridged diiron diazene complex. Chem Phys Lett 2015. [DOI: 10.1016/j.cplett.2015.09.050] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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9
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Köthe C, Braun B, Herwig C, Limberg C. Synthesis, Characterization, and Interconversion of β‐Diketiminato Nickel N
x
H
y
Complexes. Eur J Inorg Chem 2014. [DOI: 10.1002/ejic.201402812] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Claudia Köthe
- Institut für Chemie, Humboldt‐Universität zu Berlin, Brook‐Taylor‐Strasse 2, 12489 Berlin, Germany, http://www.chemie.hu‐berlin.de/aglimberg/
| | - Beatrice Braun
- Institut für Chemie, Humboldt‐Universität zu Berlin, Brook‐Taylor‐Strasse 2, 12489 Berlin, Germany, http://www.chemie.hu‐berlin.de/aglimberg/
| | - Christian Herwig
- Institut für Chemie, Humboldt‐Universität zu Berlin, Brook‐Taylor‐Strasse 2, 12489 Berlin, Germany, http://www.chemie.hu‐berlin.de/aglimberg/
| | - Christian Limberg
- Institut für Chemie, Humboldt‐Universität zu Berlin, Brook‐Taylor‐Strasse 2, 12489 Berlin, Germany, http://www.chemie.hu‐berlin.de/aglimberg/
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10
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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.
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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
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11
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Umehara K, Kuwata S, Ikariya T. N–N Bond Cleavage of Hydrazines with a Multiproton-Responsive Pincer-Type Iron Complex. J Am Chem Soc 2013; 135:6754-7. [DOI: 10.1021/ja3122944] [Citation(s) in RCA: 108] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Kazuki Umehara
- Department
of Applied Chemistry, Graduate School of
Science and Engineering, Tokyo Institute of Technology, O-okayama, Meguro-ku, Tokyo 152-8552, Japan
| | - Shigeki Kuwata
- Department
of Applied Chemistry, Graduate School of
Science and Engineering, Tokyo Institute of Technology, O-okayama, Meguro-ku, Tokyo 152-8552, Japan
| | - Takao Ikariya
- Department
of Applied Chemistry, Graduate School of
Science and Engineering, Tokyo Institute of Technology, O-okayama, Meguro-ku, Tokyo 152-8552, Japan
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12
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13
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Sokolov AY, Schaefer HF. Coordination Properties of Bridging Diazene Ligands in Unusual Diiron Complexes. Organometallics 2010. [DOI: 10.1021/om100098t] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Alexander Yu. Sokolov
- Center for Computational Quantum Chemistry, University of Georgia, Athens, Georgia 30602
| | - Henry F. Schaefer
- Center for Computational Quantum Chemistry, University of Georgia, Athens, Georgia 30602
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14
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Field LD, Li HL, Dalgarno SJ. Side-on Bound Diazene and Hydrazine Complexes of Ruthenium. Inorg Chem 2010; 49:6214-21. [DOI: 10.1021/ic100821u] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Leslie D. Field
- School of Chemistry, University of New South Wales, NSW 2052, Australia
| | - Hsiu L. Li
- School of Chemistry, University of New South Wales, NSW 2052, Australia
| | - Scott J. Dalgarno
- School of EPS-Chemistry, Heriot-Watt University, Edinburgh, Scotland EH14 4AS, U.K
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15
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Dabb S, Messerle B, Otting G, Wagler J, Willis A. Ruthenium Complexes of Substituted Hydrazine: New Solution- and Solid-State Binding Modes. Chemistry 2008; 14:10058-65. [DOI: 10.1002/chem.200801061] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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16
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Chen Y, Zhou Y, Chen P, Tao Y, Li Y, Qu J. Nitrogenase Model Complexes [Cp*Fe(μ-SR1)2(μ-η2-R2N═NH)FeCp*] (R1 = Me, Et; R2 = Me, Ph; Cp* = η5-C5Me5): Synthesis, Structure, and Catalytic N−N Bond Cleavage of Hydrazines on Diiron Centers. J Am Chem Soc 2008; 130:15250-1. [DOI: 10.1021/ja805025w] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Yanhui Chen
- State Key Laboratory of Fine Chemicals, School of Chemical Engineering, Dalian University of Technology, Dalian 116012, People’s Republic of China
| | - Yuhan Zhou
- State Key Laboratory of Fine Chemicals, School of Chemical Engineering, Dalian University of Technology, Dalian 116012, People’s Republic of China
| | - Pingping Chen
- State Key Laboratory of Fine Chemicals, School of Chemical Engineering, Dalian University of Technology, Dalian 116012, People’s Republic of China
| | - Yinsong Tao
- State Key Laboratory of Fine Chemicals, School of Chemical Engineering, Dalian University of Technology, Dalian 116012, People’s Republic of China
| | - Yang Li
- State Key Laboratory of Fine Chemicals, School of Chemical Engineering, Dalian University of Technology, Dalian 116012, People’s Republic of China
| | - Jingping Qu
- State Key Laboratory of Fine Chemicals, School of Chemical Engineering, Dalian University of Technology, Dalian 116012, People’s Republic of China
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17
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Dance I. The chemical mechanism of nitrogenase: hydrogen tunneling and further aspects of the intramolecular mechanism for hydrogenation of eta(2)-N(2) on FeMo-co to NH(3). Dalton Trans 2008:5992-8. [PMID: 19082055 DOI: 10.1039/b806103c] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The preceding paper (Dalton Trans., 2008, DOI: 10.1039/b806100a) describes the logical development of a chemical mechanism for the catalysis of hydrogenation of N(2) to 2NH(3) that occurs at the Fe(7)MoS(9)N(c)(homocitrate) cofactor (FeMo-co) of the enzyme nitrogenase. The mechanism uses a single replenishable path for serial supply of protons which become H atoms on FeMo-co, migrating to become S-H and Fe-H donors to N(2) and to the intermediates that follow. This chemical catalysis at FeMo-co is distinctly intramolecular: transition states and reaction profiles for the preferred 21 step pathway were presented. This paper describes a number of alternative intermediates and pathways that were considered in developing the mechanism. These results reveal further relevant principles of the reactivity of hydrogenated FeMo-co, and the reasons why these pathways are less likely to be part of the mechanism. The intramolecular character of the mechanism, and the relatively small distances over which H atoms transfer, lead to expectations of extensive quantum mechanical hydrogen tunneling as part of the catalytic rate enhancement. This possibility is supported by comparisons of reaction profiles with those for enzyme reactions for which tunneling is established.
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Affiliation(s)
- Ian Dance
- School of Chemistry, University of New South Wales, Sydney 2052, Australia.
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18
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Field LD, Li HL, Dalgarno SJ, Turner P. The first side-on bound metal complex of diazene, HNNH. Chem Commun (Camb) 2008:1680-2. [DOI: 10.1039/b802039f] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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19
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Dance I. The chemical mechanism of nitrogenase: calculated details of the intramolecular mechanism for hydrogenation of η2-N2 on FeMo-co to NH3. Dalton Trans 2008:5977-91. [DOI: 10.1039/b806100a] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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20
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Reiher M, Kirchner B, Hutter J, Sellmann D, Hess BA. A Photochemical Activation Scheme of Inert Dinitrogen by Dinuclear RuII and FeII Complexes. Chemistry 2004; 10:4443-53. [PMID: 15378622 DOI: 10.1002/chem.200400081] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
A general photochemical activation process of inert dinitrogen coordinated to two metal centers is presented on the basis of high-level DFT and ab initio calculations. The central feature of this activation process is the occupation of an antibonding pi* orbital upon electronic excitation from the singlet ground state S0 to the first excited singlet state S1. Populating the antibonding LUMO weakens the triple bond of dinitrogen. After a vertical excitation, the excited complex may structurally relax in the S1 state and approaches its minimum structure in the S1 state. This excited-state minimum structure features the dinitrogen bound in a diazenoid form, which exhibits a double bond and two lone pairs localized at the two nitrogen atoms, ready to be protonated. Reduction and de-excitation then yield the corresponding diazene complex; its generation represents the essential step in a nitrogen fixation and reduction protocol. The consecutive process of excitation, protonation, and reduction may be rearranged in any experimentally appropriate order. The protons needed for the reaction from dinitrogen to diazene can be provided by the ligand sphere of the complexes, which contains sulfur atoms acting as proton acceptors. These protonated thiolate functionalities bring protons close to the dinitrogen moiety. Because protonation does not change the pi*-antibonding character of the LUMO, the universal and well-directed character of the photochemical activation process makes it possible to protonate the dinitrogen complex before it is irradiated. The pi*-antibonding LUMO plays the central role in the activation process, since the diazenoid structure was obtained by excitation from various occupied orbitals as well as by a direct two-electron reduction (without photochemical activation) of the complex; that is, the important bending of N2 towards a diazenoid conformation can be achieved by populating the pi*-antibonding LUMO.
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Affiliation(s)
- Markus Reiher
- Lehrstuhl für Theoretische Chemie, Universität Bonn, Wegelerstrasse 12, 53115 Bonn, Germany.
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MacKay BA, Fryzuk MD. Dinitrogen coordination chemistry: on the biomimetic borderlands. Chem Rev 2004; 104:385-401. [PMID: 14871129 DOI: 10.1021/cr020610c] [Citation(s) in RCA: 525] [Impact Index Per Article: 26.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Bruce A MacKay
- Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, British Columbia, Canada V6T 1Z1
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QUANTUM CHEMICAL INVESTIGATIONS INTO THE PROBLEM OF BIOLOGICAL NITROGEN FIXATION: SELLMANN-TYPE METAL–SULFUR MODEL COMPLEXES. ADVANCES IN INORGANIC CHEMISTRY 2004. [DOI: 10.1016/s0898-8838(04)56003-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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