1
|
Schüren AO, Ridgway BM, Di Salvo F, Carella LM, Gramm VK, Metzger E, Doctorovich F, Rentschler E, Schünemann V, Ruschewitz U, Klein A. Structural insight into halide-coordinated [Fe 4S 4X nY 4-n] 2- clusters (X, Y = Cl, Br, I) by XRD and Mössbauer spectroscopy. Dalton Trans 2023; 52:1277-1290. [PMID: 36621931 DOI: 10.1039/d2dt03203a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Iron sulphur halide clusters [Fe4S4Br4]2- and [Fe4S4X2Y2]2- (X, Y = Cl, Br, I) were obtained in excellent yields (77 to 78%) and purity from [Fe(CO)5], elemental sulphur, I2 and benzyltrimethylammonium (BTMA+) iodide, bromide and chloride. Single crystals of (BTMA)2[Fe4S4Br4] (1), (BTMA)2[Fe4S4Br2Cl2] (2), (BTMA)2[Fe4S4Cl2I2] (3), and (BTMA)2[Fe4S4Br2I2] (4) were isostructural to the previously reported (BTMA)2[Fe4S4I4] (5) (monoclinic, Cc). Instead of the chloride cubane cluster [Fe4S4Cl4]2-, we found the prismane-shaped cluster (BTMA)3[Fe6S6Cl6] (6) (P1̄). 57Fe Mössbauer spectroscopy indicates complete delocalisation with Fe2.5+ oxidation states for all iron atoms. Magnetic measurements showed small χMT values at 298 K ranging from 1.12 to 1.54 cm3 K mol-1, indicating the dominant antiferromagnetic exchange interactions. With decreasing temperature, the χMT values decreased to reach a plateau at around 100 K. From about 20 K, the values drop significantly. Fitting the data in the Heisenberg-Dirac-van Vleck (HDvV) as well as the Heisenberg Double Exchange (HDE) formalism confirmed the delocalisation and antiferromagnetic coupling assumed from Mössbauer spectroscopy.
Collapse
Affiliation(s)
- Andreas O Schüren
- Universität zu Köln, Mathematisch-Naturwissenschaftliche Fakultät, Department für Chemie, Institut für Anorganische Chemie, Greinstraße 6, D-50939 Köln, Germany. .,INQUIMAE-CONICET-Universidad de Buenos Aires, Intendente Güiraldes 2160, Pabellón 2, Piso 3, C1428EGA, Buenos Aires, Argentina
| | - Benjamin M Ridgway
- INQUIMAE-CONICET-Universidad de Buenos Aires, Intendente Güiraldes 2160, Pabellón 2, Piso 3, C1428EGA, Buenos Aires, Argentina
| | - Florencia Di Salvo
- INQUIMAE-CONICET-Universidad de Buenos Aires, Intendente Güiraldes 2160, Pabellón 2, Piso 3, C1428EGA, Buenos Aires, Argentina.,Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento de Química Inorgánica, Analítica y Química Física, Intendente Güiraldes 2160, Pabellón 2, Piso 3, C1428EGA, Buenos Aires, Argentina
| | - Luca M Carella
- Johannes Gutenberg Universität Mainz, Department Chemie, Duesbergweg 10-14, 55128 Mainz, Germany
| | - Verena K Gramm
- Universität zu Köln, Mathematisch-Naturwissenschaftliche Fakultät, Department für Chemie, Institut für Anorganische Chemie, Greinstraße 6, D-50939 Köln, Germany.
| | - Elisa Metzger
- TU Kaiserlautern Department of Physics, 67663 Kaiserlautern, Germany
| | - Fabio Doctorovich
- INQUIMAE-CONICET-Universidad de Buenos Aires, Intendente Güiraldes 2160, Pabellón 2, Piso 3, C1428EGA, Buenos Aires, Argentina.,Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Departamento de Química Inorgánica, Analítica y Química Física, Intendente Güiraldes 2160, Pabellón 2, Piso 3, C1428EGA, Buenos Aires, Argentina
| | - Eva Rentschler
- Johannes Gutenberg Universität Mainz, Department Chemie, Duesbergweg 10-14, 55128 Mainz, Germany
| | - Volker Schünemann
- TU Kaiserlautern Department of Physics, 67663 Kaiserlautern, Germany
| | - Uwe Ruschewitz
- Universität zu Köln, Mathematisch-Naturwissenschaftliche Fakultät, Department für Chemie, Institut für Anorganische Chemie, Greinstraße 6, D-50939 Köln, Germany.
| | - Axel Klein
- Universität zu Köln, Mathematisch-Naturwissenschaftliche Fakultät, Department für Chemie, Institut für Anorganische Chemie, Greinstraße 6, D-50939 Köln, Germany.
| |
Collapse
|
2
|
Affiliation(s)
- Oliver Einsle
- Institute for Biochemistry, Albert-Ludwigs-University Freiburg, 79104 Freiburg, Germany
| | - Douglas C. Rees
- Division of Chemistry and Chemical Engineering, Howard Hughes Medical Institute, California Institute of Technology, Pasadena California 91125, United States
| |
Collapse
|
3
|
Survey of the Geometric and Electronic Structures of the Key Hydrogenated Forms of FeMo-co, the Active Site of the Enzyme Nitrogenase: Principles of the Mechanistically Significant Coordination Chemistry. INORGANICS 2019. [DOI: 10.3390/inorganics7010008] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The enzyme nitrogenase naturally hydrogenates N2 to NH3, achieved through the accumulation of H atoms on FeMo-co, the Fe7MoS9C(homocitrate) cluster that is the catalytically active site. Four intermediates, E1H1, E2H2, E3H3, and E4H4, carry these hydrogen atoms. I report density functional calculations of the numerous possibilities for the geometric and electronic structures of these poly-hydrogenated forms of FeMo-co. This survey involves more than 100 structures, including those with bound H2, and assesses their relative energies and most likely electronic states. Twelve locations for bound H atoms in the active domain of FeMo-co, including Fe–H–Fe and Fe–H–S bridges, are studied. A significant result is that transverse Fe–H–Fe bridges (transverse to the pseudo-threefold axis of FeMo-co and shared with triply-bridging S) are not possible geometrically unless the S is hydrogenated to become doubly-bridging. The favourable Fe–H–Fe bridges are shared with doubly-bridging S. ENDOR data for an E4H4 intermediate trapped at low temperature, and interpretations in terms of the geometrical and electronic structure of E4H4, are assessed in conjunction with the calculated possibilities. The results reported here yield a set of 24 principles for the mechanistically significant coordination chemistry of H and H2 on FeMo-co, in the stages prior to N2 binding.
Collapse
|
4
|
Dance I. What is the role of the isolated small water pool near FeMo‐co, the active site of nitrogenase? FEBS J 2018; 285:2972-2986. [DOI: 10.1111/febs.14519] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2018] [Revised: 05/02/2018] [Accepted: 05/22/2018] [Indexed: 01/14/2023]
Affiliation(s)
- Ian Dance
- School of Chemistry UNSW Sydney NSW Australia
| |
Collapse
|
5
|
X-ray crystal structures of [NHR3]2[Fe4S4X4] (X = PhS, R = Et or n Bu; X = Cl, R = n Bu): implications for sites of protonation in Fe–S clusters. TRANSIT METAL CHEM 2016. [DOI: 10.1007/s11243-016-0052-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
|
6
|
Al-Rammahi TMM, Henderson RA. Binding small molecules and ions to [Fe4S4Cl4](2-) modulates rate of protonation of the cluster. Dalton Trans 2016; 45:1373-81. [PMID: 26661750 DOI: 10.1039/c5dt04523a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The mechanism of the acid-catalyzed substitution reaction of the terminal chloro-ligands in [Fe4S4Cl4](2-) by PhS(-) in the presence of NHBu(n)3(+) involves rate-limiting proton transfer from NHBu(n)3(+) to the cluster (k0 = 490 ± 20 dm(3) mol(-1) s(-1)). A variety of small molecules and ions (L = substrate = Cl(-), Br(-), I(-), RNHNH2 (R = Me or Ph), Me2NNH2, HCN, NCS(-), N3(-), Bu(t)NC or pyridine) bind to [Fe4S4Cl4](2-) and this affects the rate of subsequent protonation of [Fe4S4Cl4(L)](n-). Where the kinetics allow, the equilibrium constants for the substrates binding to [Fe4S4Cl4](2-) (K(L)) and the rates of proton transfer from NHBu(n)3(+) to [Fe4S4Cl4(L)](n-) (k) have been determined. The results indicate the following general features. (i) Bound substrates increase the rate of protonation of the cluster, but the rate increase is modest (k/k0 = 1.6 to ≥72). (ii) When K(L) is small, so is k/k0. (iii) Binding substrates which are good σ-donors or good π-acceptors lead to the largest k/k0. This behaviour is discussed in terms of the recent proposal that protonation of [Fe4S4Cl4](2-) at a μ3-S, is coupled to concomitant Fe-(μ3-SH) bond elongation/cleavage.
Collapse
Affiliation(s)
- Thaer M M Al-Rammahi
- School of Chemistry, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK. and Department of Chemistry, College of Science, University of Kerbala, Kerbala, Iraq
| | - Richard A Henderson
- School of Chemistry, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK.
| |
Collapse
|
7
|
Schüren AO, Gramm VK, Dürr M, Foi A, Ivanović-Burmazović I, Doctorovich F, Ruschewitz U, Klein A. Halide coordinated homoleptic [Fe4S4X4](2-) and heteroleptic [Fe4S4X2Y2](2-) clusters (X, Y = Cl, Br, I)--alternative preparations, structural analogies and spectroscopic properties in solution and solid state. Dalton Trans 2016; 45:361-75. [PMID: 26618565 DOI: 10.1039/c5dt02769a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
New facile methods to prepare iron sulphur halide clusters [Fe4S4X4](2-) from [Fe(CO)5] and elemental sulphur were elaborated. Reactions of ferrous precursors like tetrahalidoferrates(ii) or simple ferrous halides with [Fe(CO)5] and sulphur turned out to be efficient methods to prepare homoleptic [Fe4S4X4](2-) (X = Cl, Br) and heteroleptic clusters [Fe4S4X4-nYn](2-) (X = Cl, Br; Y = Br, I). Solid materials were obtained as salts of BTMA(+) (= benzyltrimethylammonium); the new compounds containing [Fe4S4Br4](2-) and [Fe4S4X2Y2](2-) (X, Y = Cl, Br, I) were all isostructural to (BTMA)2[Fe4S4I4] (monoclinic, Cc) as inferred from synchrotron X-ray powder diffraction. While the solid materials contain defined heteroleptic clusters with a halide X : Y ratio of 2 : 2, dissolving these compounds leads to rapid scrambling of the halide ligands forming mixtures of all five possible [Fe4S4X4-nYn](2-) clusters as could be shown by UHR-ESI MS. The variation of X and Y allowed assignment of the absorption bands in the visible and NIR; the long-wavelength bands around 1100 nm were tentatively assigned to intervalence charge transfer (IVCT) transitions.
Collapse
Affiliation(s)
- Andreas O Schüren
- Department für Chemie, Institut für Anorganische Chemie, Universität zu Köln, Greinstraße 6, 50939 Köln, Germany. and Departamento de Química Inorgánica, Analítica, y Química Física, Facultad de Ciencias Exactas y Naturales, INQUIMAE-CONICET, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón 2, Piso 3, C1428EHA Buenos Aires, Argentina
| | - Verena K Gramm
- Department für Chemie, Institut für Anorganische Chemie, Universität zu Köln, Greinstraße 6, 50939 Köln, Germany.
| | - Maximilian Dürr
- Department Chemie und Pharmazie, Lehrstuhl für Bioanorgansiche Chemie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 1, 91058 Erlangen, Germany
| | - Ana Foi
- Departamento de Química Inorgánica, Analítica, y Química Física, Facultad de Ciencias Exactas y Naturales, INQUIMAE-CONICET, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón 2, Piso 3, C1428EHA Buenos Aires, Argentina
| | - Ivana Ivanović-Burmazović
- Department Chemie und Pharmazie, Lehrstuhl für Bioanorgansiche Chemie, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstraße 1, 91058 Erlangen, Germany
| | - Fabio Doctorovich
- Departamento de Química Inorgánica, Analítica, y Química Física, Facultad de Ciencias Exactas y Naturales, INQUIMAE-CONICET, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón 2, Piso 3, C1428EHA Buenos Aires, Argentina
| | - Uwe Ruschewitz
- Department für Chemie, Institut für Anorganische Chemie, Universität zu Köln, Greinstraße 6, 50939 Köln, Germany.
| | - Axel Klein
- Department für Chemie, Institut für Anorganische Chemie, Universität zu Köln, Greinstraße 6, 50939 Köln, Germany.
| |
Collapse
|
8
|
Al-Rammahi TMM, Henderson RA. Exploring the acid-catalyzed substitution mechanism of [Fe4S4Cl4]2−. Dalton Trans 2016; 45:307-14. [DOI: 10.1039/c5dt04008f] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Kinetic studies focussing on either the protonation or substitution step of the acid catalyzed substitution reactions of [Fe4S4Cl4]2− support a mechanism involving concomitant cluster protonation and Fe–(μ3-SH) bond cleavage.
Collapse
|
9
|
Abstract
![]()
The iron–molybdenum cofactor of nitrogenase has unprecedented
coordination chemistry, including a high-spin iron cluster called
the iron-molybdenum cofactor (FeMoco). Thus, understanding the mechanism
of nitrogenase challenges coordination chemists to understand the
fundamental N2 chemistry of high-spin iron sites. This
Account summarizes a series of studies in which we have synthesized
a number of new compounds with multiple iron atoms, characterized
them using crystallography and spectroscopy, and studied their reactions
in detail. These studies show that formally iron(I) and iron(0) complexes
with three- and four-coordinate metal atoms have the ability to weaken
and break the triple bond of N2. These reactions occur
at or below room temperature, indicating that they are kinetically
facile. This in turn implies that iron sites in the FeMoco are chemically
reasonable locations for N2 binding and reduction. The careful evaluation of these compounds and their reaction pathways
has taught important lessons about what characteristics make iron
more effective for N2 activation. Cooperation of two iron
atoms can lengthen and weaken the N–N bond, while three working
together enables iron atoms to completely cleave the N–N bond
to nitrides. Alkali metals (typically introduced into the reaction
as part of the reducing agent) are thermodynamically useful because
the alkali metal cations stabilize highly reduced complexes, pull
electron density into the N2 unit, and make reduced nitride
products more stable. Alkali metals can also play a kinetic role,
because cation−π interactions with the supporting ligands
can hold iron atoms near enough to one another to facilitate the cooperation
of multiple iron atoms. Many of these principles may also be relevant
to the iron-catalyzed Haber–Bosch process, at which collections
of iron atoms (often promoted by the addition of alkali metals) break
the N–N bond of N2. The results of these studies
teach more general lessons as well.
They have demonstrated that N2 can be a redox-active ligand,
accepting spin and electron density in complexes of N22–. They have shown the power of cooperation between
multiple transition metals, and also between alkali metals and transition
metals. Finally, alkali metal based cation−π interactions
have the potential to be broadly useful for bringing metals close
together with sufficient flexibility to allow multistep, multielectron
reactions. At the same time, the positive charge on the alkali metal
cation stabilizes charge buildup in intermediates.
Collapse
Affiliation(s)
- Sean F. McWilliams
- Department of Chemistry, Yale University, New Haven, Connecticut 06511, United States
| | - Patrick L. Holland
- Department of Chemistry, Yale University, New Haven, Connecticut 06511, United States
| |
Collapse
|
10
|
Saouma CT, Morris WD, Darcy JW, Mayer JM. Protonation and Proton-Coupled Electron Transfer at S-Ligated [4Fe-4S] Clusters. Chemistry 2015; 21:9256-60. [PMID: 25965413 DOI: 10.1002/chem.201500152] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2015] [Indexed: 11/12/2022]
Abstract
Biological [Fe-S] clusters are increasingly recognized to undergo proton-coupled electron transfer (PCET), but the site of protonation, mechanism, and role for PCET remains largely unknown. Here we explore this reactivity with synthetic model clusters. Protonation of the arylthiolate-ligated [4Fe-4S] cluster [Fe4 S4 (SAr)4 ](2-) (1, SAr=S-2,4-6-(iPr)3 C6 H2 ) leads to thiol dissociation, reversibly forming [Fe4 S4 (SAr)3 L](1-) (2) and ArSH (L=solvent, and/or conjugate base). Solutions of 2+ArSH react with the nitroxyl radical TEMPO to give [Fe4 S4 (SAr)4 ](1-) (1ox ) and TEMPOH. This reaction involves PCET coupled to thiolate association and may proceed via the unobserved protonated cluster [Fe4 S4 (SAr)3 (HSAr)](1-) (1-H). Similar reactions with this and related clusters proceed comparably. An understanding of the PCET thermochemistry of this cluster system has been developed, encompassing three different redox levels and two protonation states.
Collapse
Affiliation(s)
- Caroline T Saouma
- Department of Chemistry, University of Washington, Box 351700, Seattle, WA 98195 (USA). .,Department of Chemistry, University of Utah, 315 S 1400 E Room 2020, Salt Lake City, UT 84112 (USA).
| | - Wesley D Morris
- Department of Chemistry, Yale University, 225 Prospect St., PO Box 208107, New Haven, CT 06520 (USA)
| | - Julia W Darcy
- Department of Chemistry, Yale University, 225 Prospect St., PO Box 208107, New Haven, CT 06520 (USA)
| | - James M Mayer
- Department of Chemistry, University of Washington, Box 351700, Seattle, WA 98195 (USA). .,Department of Chemistry, Yale University, 225 Prospect St., PO Box 208107, New Haven, CT 06520 (USA).
| |
Collapse
|
11
|
Dance I. The pathway for serial proton supply to the active site of nitrogenase: enhanced density functional modeling of the Grotthuss mechanism. Dalton Trans 2015; 44:18167-86. [DOI: 10.1039/c5dt03223g] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Proton translocation along a chain of eight waters to the active site of nitrogenase is described in detail, using density functional simulations with a 269 atom system that includes surrounding amino acids.
Collapse
Affiliation(s)
- Ian Dance
- School of Chemistry
- UNSW Australia
- Sydney 2052
- Australia
| |
Collapse
|
12
|
Dance I. Misconception of reductive elimination of H2, in the context of the mechanism of nitrogenase. Dalton Trans 2015; 44:9027-37. [DOI: 10.1039/c5dt00771b] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Calculated atom partial charges reveal misconceptions of reductive elimination of H2.
Collapse
Affiliation(s)
- Ian Dance
- School of Chemistry
- University of New South Wales
- Sydney 2052
- Australia
| |
Collapse
|
13
|
Dance I. Protonation of bridging sulfur in cubanoid Fe4S4 clusters causes large geometric changes: the theory of geometric and electronic structure. Dalton Trans 2015; 44:4707-17. [DOI: 10.1039/c4dt03681f] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Density functional calculations indicate that protonation of a μ3-S atom in cubanoid clusters [Fe4S4X4]2− leads to a large extension of one Fe–S(H) bond such that the SH ligand is doubly-bridging, μ-SH.
Collapse
Affiliation(s)
- Ian Dance
- School of Chemistry
- University of New South Wales
- Sydney 2052
- Australia
| |
Collapse
|
14
|
Dance I. What is the trigger mechanism for the reversal of electron flow in oxygen-tolerant [NiFe] hydrogenases? Chem Sci 2014; 6:1433-1443. [PMID: 29560232 PMCID: PMC5811149 DOI: 10.1039/c4sc03223c] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2014] [Accepted: 12/08/2014] [Indexed: 11/21/2022] Open
Abstract
A new mechanistic model is developed for the sequence of events by which oxygen-tolerant [NiFe] hydrogenase enzymes respond to O2.
The [NiFe] hydrogenases use an electron transfer relay of three FeS clusters – proximal, medial and distal – to release the electrons from the principal reaction, H2 → 2H+ + 2e–, that occurs at the Ni–Fe catalytic site. This site is normally inactivated by O2, but the subclass of O2-tolerant [NiFe] hydrogenases are able to counter this inactivation through the agency of an unusual and unprecedented proximal cluster, with composition [Fe4S3(Scys)6], that is able to transfer two electrons back to the Ni–Fe site and effect crucial reduction of O2-derived species and thereby reactivate the Ni–Fe site. This proximal cluster gates both the direction and the number of electrons flowing through it, and can reverse the normal flow during O2 attack. The unusual structures and redox potentials of the proximal cluster are known: a structural change in the proximal cluster causes changes in its electron-transfer potentials. Using protein structure analysis and density functional simulations, this paper identifies a closed protonic system comprising the proximal cluster, some contiguous residues, and a proton reservoir, and proposes that it is activated by O2-induced conformational change at the Ni–Fe site. This change is linked to a key histidine residue which then causes protonation of the proximal cluster, and migration of this proton to a key μ3-S atom. The resulting SH group causes the required structural change at the proximal cluster, modifying its redox potentials, and leads to the reversed electron flow back to the Ni–Fe site. This cycle is reversible, and the protons involved are independent of those used or produced in reactions at the active site. Existing experimental support for this model is cited, and new testing experiments are suggested.
Collapse
Affiliation(s)
- Ian Dance
- School of Chemistry , University of New South Wales , Sydney 2052 , Australia .
| |
Collapse
|