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Chiesa M, Giamello E, Murphy DM, Pacchioni G, Paganini MC, Soave R, Sojka Z. Reductive Activation of the Nitrogen Molecule at the Surface of “Electron-Rich” MgO and CaO. The N2-Surface Adsorbed Radical Ion. J Phys Chem B 2001. [DOI: 10.1021/jp002794+] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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52
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Nishibayashi Y, Takemoto S, Iwai S, Hidai M. Formation of ammonia in the reactions of a tungsten dinitrogen with ruthenium dihydrogen complexes under mild reaction conditions. Inorg Chem 2000; 39:5946-57. [PMID: 11151496 DOI: 10.1021/ic000799f] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Treatment of cis-[W(N2)2(PMe2Ph)4] (5) with an equilibrium mixture of trans-[RuCl(eta 2-H2)(dppp)2]X (3) with pKa = 4.4 and [RuCl(dppp)2]X (4) [X = PF6, BF4, or OTf; dppp = 1,3-bis(diphenylphosphino)propane] containing 10 equiv of the Ru atom based on tungsten in benzene-dichloroethane at 55 degrees C for 24 h under 1 atm of H2 gave NH3 in 45-55% total yields based on tungsten, together with the formation of trans-[RuHCl(dppp)2] (6). Free NH3 in 9-16% yields was observed in the reaction mixture, and further NH3 in 36-45% yields was released after base distillation. Detailed studies on the reaction of 5 with numerous Ru(eta 2-H2) complexes showed that the yield of NH3 produced critically depended upon the pKa value of the employed Ru(eta 2-H2) complexes. When 5 was treated with 10 equiv of trans-[RuCl(eta 2-H2)(dppe)2]X (8) with pKa = 6.0 [X = PF6, BF4, or OTf; dppe = 1,2-bis(diphenylphosphino)ethane] under 1 atm of H2, NH3 was formed in higher yields (up to 79% total yield) compared with the reaction with an equilibrium mixture of 3 and 4. If the pKa value of a Ru(eta 2-H2) complex was increased up to about 10, the yield of NH3 was remarkably decreased. In these reactions, heterolytic cleavage of H2 seems to occur at the Ru center via nucleophilic attack of the coordinated N2 on the coordinated H2 where a proton (H+) is used for the protonation of the coordinated N2 and a hydride (H-) remains at the Ru atom. Treatment of 5, trans-[W(N2)2(PMePh2)4] (14), or trans-[M(N2)2(dppe)2] [M = Mo (1), W (2)] with Ru(eta 2-H2) complexes at room temperature led to isolation of intermediate hydrazido(2-) complexes such as trans-[W(OTf)(NNH2)(PMe2Ph)4]OTf (19), trans-[W(OTf)(NNH2)(PMePh2)4]OTf (20), and trans-[WX(NNH2)(dppe)2]+ [X = OTf (15), F (16)]. The molecular structure of 19 was determined by X-ray analysis. Further ruthenium-assisted protonation of hydrazido(2-) intermediates such as 19 with H2 at 55 degrees C was considered to result in the formation of NH3, concurrent with the generation of W(VI) species. All of the electrons required for the reduction of N2 are provided by the zerovalent tungsten.
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Affiliation(s)
- Y Nishibayashi
- Department of Chemistry and Biotechnology, Graduate School of Engineering, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
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53
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Affiliation(s)
- Thomas H. Rod
- Contribution from the Center for Atomic-scale Materials Physics (CAMP), Department of Physics, Building 307, Technical University of Denmark, DK-2800 Lyngby, Denmark
| | - Jens K. Nørskov
- Contribution from the Center for Atomic-scale Materials Physics (CAMP), Department of Physics, Building 307, Technical University of Denmark, DK-2800 Lyngby, Denmark
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54
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Szilagyi R, Musaev D, Morokuma K. Theoretical studies of biological nitrogen fixation. Part II. Hydrogen bonded networks as possible reactant and product channels. ACTA ACUST UNITED AC 2000. [DOI: 10.1016/s0166-1280(00)00407-3] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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55
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The nitrogenase catalyzed N2 dependent HD formation: a model reaction and its significance for the FeMoco function. Coord Chem Rev 2000. [DOI: 10.1016/s0010-8545(99)00240-4] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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56
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Agapie T, Odom AL, Cummins CC. In pursuit of the molybdenum(III) tris(thiolate) fragment: unusual structure of a dimolybdenum mu-nitrido complex. Inorg Chem 2000; 39:174-9. [PMID: 11272522 DOI: 10.1021/ic9904891] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The new molybdenum nitrido-thiolate complex N triple bond Mo(SAd)3 (Ad = 1-adamantyl) was prepared by a ligand exchange route involving reaction of Ti(SAd)(OiPr)3 with Chisholm's nitrido-butoxide complex N triple bond Mo(OtBu)3. In an effort to abstract the nitrido nitrogen from N triple bond Mo(SAd)3, the compound was treated with Mo(N[tBu]Ph)3, a three-coordinate molybdenum(III) complex. This resulted in formation of the unusual and thermally unstable (mu-nitrido)dimolybdenum complex (AdS)3Mo(mu-N)Mo(N[tBu]Ph)3, which was isolated and characterized. An X-ray study revealed (AdS)3Mo(mu-N)Mo(N[tBu]Ph)3 to possess an unsymmetrical Mo-(mu-N)-Mo linkage, the Mo-thiolate fragment exhibiting a substantially longer bond to the bridging nitrogen atom. The structure of (AdS)3Mo-(mu-N)Mo(N[tBu]Ph)3 is noteworthy, displaying trigonal monopyramidal coordination at the (mu-N)-Mo-thiolate Mo center. Since N triple bond Mo(N[tBu]Ph)3 is a good leaving group, (AdS)3Mo(mu-N)Mo(N[tBu]Ph)3 should be a source of the reactive Mo(SAd)3 fragment. In all the studied reactions of the (mu-nitrido)dimolybdenum complex one of the observed products was N triple bond Mo(N[tBu]Ph)3. Two products containing the Mo(SAd)3 fragment were observed: (AdS)3Mo triple bond Mo(SAd)3 and [(ON)Mo(mu-SAd)(SAd)2]2. Upon treatment with pyridine, the tris(thio-1-adamantyl)-(nitrosyl)molybdenum dimer forms the pyridine adduct (AdS)3Mo(NO)(py), which is a monomer.
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Affiliation(s)
- T Agapie
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge 02139-4307, USA
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Mayer SM, Lawson DM, Gormal CA, Roe SM, Smith BE. New insights into structure-function relationships in nitrogenase: A 1.6 A resolution X-ray crystallographic study of Klebsiella pneumoniae MoFe-protein. J Mol Biol 1999; 292:871-91. [PMID: 10525412 DOI: 10.1006/jmbi.1999.3107] [Citation(s) in RCA: 234] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The X-ray crystal structure of Klebsiella pneumoniae nitrogenase component 1 (Kp1) has been determined and refined to a resolution of 1.6 A, the highest resolution reported for any nitrogenase structure. Models derived from three 1.6 A resolution X-ray data sets are described; two represent distinct oxidation states, whilst the third appears to be a mixture of both oxidized and reduced states (or perhaps an intermediate state). The structures of the protein and the iron-molybdenum cofactor (FeMoco) appear to be largely unaffected by the redox status, although the movement of Ser beta90 and a surface helix in the beta subunit may be of functional significance. By contrast, the 8Fe-7S P-cluster undergoes discrete conformational changes involving the movement of two iron atoms. Comparisons with known component 1 structures reveal subtle differences in the FeMoco environment, which could account for the lower midpoint potential of this cluster in Kp1. Furthermore, a non-proline- cis peptide bond has been identified in the alpha subunit that may have a functional role. It is within 10 A of the FeMoco and may have been overlooked in other component 1 models. Finally, metal-metal and metal-sulphur distances within the metal clusters agree well with values derived from EXAFS studies, although they are generally longer than the values reported for the closely related protein from Azotobacter vinelandii. A number of bonds between the clusters and their ligands are distinctly longer than the EXAFS values, in particular, those involving the molybdenum atom of the FeMoco.
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Affiliation(s)
- S M Mayer
- John Innes Centre, Nitrogen Fixation Laboratory, Norwich, NR4 7UH, UK
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60
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Sellmann D, Utz J, Blum N, Heinemann FW. On the function of nitrogenase FeMo cofactors and competitive catalysts: chemical principles, structural blue-prints, and the relevance of iron sulfur complexes for N2 fixation. Coord Chem Rev 1999. [DOI: 10.1016/s0010-8545(99)00108-3] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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61
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McGrady JE, Stranger R. Redox-Induced Formation and Cleavage of O-O sigma and pi Bonds in a Peroxo-Bridged Manganese Dimer: A Density Functional Study. Inorg Chem 1999; 38:550-558. [PMID: 11673961 DOI: 10.1021/ic981253k] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The structural and electronic consequences of reduction and oxidation of a peroxo-bridged Mn(2)(IV/IV) dimer, Mn(2)(&mgr;-O)(2)(&mgr;-O(2))(NH(3))(6)(2+), are examined using approximate density functional theory. In both cases, the initial electron-transfer step is localized on the metal centers, but subsequent structural rearrangement results in transfer of the excess charge to the &mgr;-O(2) unit, with concomitant regeneration of the Mn(2)(IV/IV) core. Two-electron reduction results in population of the O-O sigma orbital and complete cleavage of the O-O bond, whereas two-electron oxidation depopulates the O-O pi orbital, forming molecular oxygen. The coupling between the metal centers (antiferromagnetic or ferromagnetic) affects the stability of the intermediate species, in which the redox process is metal based, and hence influences the kinetic barrier to bond formation or cleavage. Reductive cleavage of the O-O sigma bond is favored when the metal centers are antiferromagnetically coupled, whereas oxidative formation of the pi component of the O-O bond is favored by ferromagnetic coupling. The possible implications for the relationship between structure and function in the oxygen-evolving complex found in photosynthetic organisms are discussed.
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Affiliation(s)
- John E. McGrady
- Department of Chemistry, The Faculties, The Australian National University, Canberra, ACT 0200, Australia
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62
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Smith BE. Structure, Function, and Biosynthesis of the Metallosulfur Clusters in Nitrogenases. ADVANCES IN INORGANIC CHEMISTRY 1999. [DOI: 10.1016/s0898-8838(08)60078-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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63
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Satcher JH, Olmstead MM, Droege MW, Parkin SR, Noll BC, May L, Balch AL. Novel Square Arrangements in Tetranuclear and Octanuclear Iron(III) Complexes with Asymmetric Iron Environments Created by the Unsymmetric Bridging Ligand N,N,N'-Tris((N-methyl)-2-benzimidazolylmethyl)-N'-methyl-1,3-diamino-2-propanol. Inorg Chem 1998; 37:6751-6758. [PMID: 11670809 DOI: 10.1021/ic9802404] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The synthesis and characterization of novel tetranuclear and octanuclear iron(III) complexes with structures based on a nearly square arrangement of four iron ions are reported. Reaction of ferric nitrate, sodium acetate, and the unsymmetrical binucleating ligand HBMDP, where HBMDP is N,N,N'-tris((N-methyl)-2-benzimidazolylmethyl)-N'-methyl-1,3-diamino-2-propanol, in acetone/water yields the tetranuclear iron complex [Fe(4)(&mgr;-O)(2)(&mgr;-BMDP)(2)(&mgr;-OAc)(2)](4+), which exhibits coordination number asymmetry. The structure of [Fe(4)(&mgr;-O)(2)(&mgr;-BMDP)(2)(&mgr;-OAc)(2)](NO(3))(3)(OH).12H(2)O has been determined by single-crystal X-ray diffraction. Each (&mgr;-BMDP) ligand spans two iron(III) ions and causes these ions to become structurally distinct. Within this binuclear unit one iron atom is five-coordinate with distorted square pyramidal geometry and an N(2)O(3) donor set, while the other iron is six-coordinate with distorted octahedral geometry and an N(3)O(3) donor set. Two of these binuclear units are linked through a pair of oxo and acetato bridges to form the centrosymmetric tetranuclear complex. The coordinatively nonequivalent iron atoms exhibit distinct Mössbauer spectroscopic parameters and produce a pair of doublets at 80 K. The iron(III) centers are coupled antiferromagnetically with a room-temperature moment of 1.9 &mgr;(B) per iron with J = -103.3 cm(-)(1), zJ' = -105.9 cm(-)(1). The properties of the unsymmetric cation [Fe(4)(&mgr;-O)(2)(&mgr;-BMDP)(2)(&mgr;-OAc)(2)](4+) are similar to those observed for binuclear iron proteins with comparable coordinative inequivalence. Efforts to increase the solubility of [Fe(4)(&mgr;-O)(2)(&mgr;-BMDP)(2)(&mgr;-OAc)(2)](4+) by metathesis with sodium tetrafluoroborate resulted in the isolation of crystals of a new octanuclear iron species, [Fe(8)(&mgr;-O)(4)(&mgr;-BMDP)(4)(OH)(4)(&mgr;-OAc)(4)](BF(4))(3)(OH).2CH(3)CN.8H(2)O( )()(2), which has also been characterized by single-crystal X-ray diffraction. The asymmetric unit consists of an Fe(2)(&mgr;-O)(&mgr;-BMDP)(&mgr;-OAc)(OH) group which is externally bridged via the oxo ions to form a molecular square with four of the eight iron ions at the corners. Both iron sites are six-coordinate with distorted octahedral geometry. One has an N(2)O(4) donor set; the other has an N(3)O(3) donor set.
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Affiliation(s)
- Joe H. Satcher
- Lawrence Livermore National Laboratory, Livermore, California 94550, and Departments of Chemistry, University of California Davis, Davis California, 95616, and The Catholic University of America, Washington, D.C. 20064
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64
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Siegbahn PEM, Westerberg J, Svensson M, Crabtree RH. Nitrogen Fixation by Nitrogenases: A Quantum Chemical Study. J Phys Chem B 1998. [DOI: 10.1021/jp972207t] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Per E. M. Siegbahn
- Department of Physics, Stockholm University, Box 6730, S-113 85 Stockholm, Sweden
| | - Joakim Westerberg
- Department of Physics, Stockholm University, Box 6730, S-113 85 Stockholm, Sweden
| | - Mats Svensson
- Department of Chemistry, Organic Chemistry, Royal Institute of Technology, S-100 44 Stockholm, Sweden
| | - Robert H. Crabtree
- Chemistry Department, Yale University, 225 Prospect Street, New Haven, Connecticut 06520-8107
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65
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Sellmann D, Sutter J. In Quest of Competitive Catalysts for Nitrogenases and Other Metal Sulfur Enzymes. Acc Chem Res 1997. [DOI: 10.1021/ar960158h] [Citation(s) in RCA: 208] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Dieter Sellmann
- Institut für Anorganische Chemie der Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstrasse 1, D-91058 Erlangen, Germany
| | - Jörg Sutter
- Institut für Anorganische Chemie der Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstrasse 1, D-91058 Erlangen, Germany
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66
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Lee HI, Cameron LM, Hales BJ, Hoffman BM. CO Binding to the FeMo Cofactor of CO-Inhibited Nitrogenase: 13CO and 1H Q-Band ENDOR Investigation. J Am Chem Soc 1997. [DOI: 10.1021/ja9715096] [Citation(s) in RCA: 102] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Hong-In Lee
- Contribution from the Departments of Chemistry, Northwestern University, Evanston, Illinois 60208, and Louisiana State University, Baton Rouge, Louisiana 70803
| | - Linda M. Cameron
- Contribution from the Departments of Chemistry, Northwestern University, Evanston, Illinois 60208, and Louisiana State University, Baton Rouge, Louisiana 70803
| | - Brian J. Hales
- Contribution from the Departments of Chemistry, Northwestern University, Evanston, Illinois 60208, and Louisiana State University, Baton Rouge, Louisiana 70803
| | - Brian M. Hoffman
- Contribution from the Departments of Chemistry, Northwestern University, Evanston, Illinois 60208, and Louisiana State University, Baton Rouge, Louisiana 70803
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67
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Malinak SM, Simeonov AM, Mosier PE, McKenna CE, Coucouvanis D. Catalytic Reduction of cis-Dimethyldiazene by the [MoFe3S4]3+ Clusters. The Four-Electron Reduction of a NN Bond by a Nitrogenase-Relevant Cluster and Implications for the Function of Nitrogenase. J Am Chem Soc 1997. [DOI: 10.1021/ja963475s] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Steven M. Malinak
- Contribution from the Department of Chemistry, The University of Michigan, Ann Arbor, Michigan 48109-1055, and Department of Chemistry, The University of Southern California, Los Angeles, California 90089-0744
| | - Anton M. Simeonov
- Contribution from the Department of Chemistry, The University of Michigan, Ann Arbor, Michigan 48109-1055, and Department of Chemistry, The University of Southern California, Los Angeles, California 90089-0744
| | - Patrick E. Mosier
- Contribution from the Department of Chemistry, The University of Michigan, Ann Arbor, Michigan 48109-1055, and Department of Chemistry, The University of Southern California, Los Angeles, California 90089-0744
| | - Charles E. McKenna
- Contribution from the Department of Chemistry, The University of Michigan, Ann Arbor, Michigan 48109-1055, and Department of Chemistry, The University of Southern California, Los Angeles, California 90089-0744
| | - Dimitri Coucouvanis
- Contribution from the Department of Chemistry, The University of Michigan, Ann Arbor, Michigan 48109-1055, and Department of Chemistry, The University of Southern California, Los Angeles, California 90089-0744
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69
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Holm RH, Kennepohl P, Solomon EI. Structural and Functional Aspects of Metal Sites in Biology. Chem Rev 1996; 96:2239-2314. [PMID: 11848828 DOI: 10.1021/cr9500390] [Citation(s) in RCA: 1850] [Impact Index Per Article: 66.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Richard H. Holm
- Departments of Chemistry, Harvard University, Cambridge, Massachusetts 02138, and Stanford University, Stanford, California 94305
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70
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Affiliation(s)
- Barbara K. Burgess
- Department of Molecular Biology and Biochemistry, University of California, Irvine, California 92717-3900, and Nitrogen Fixation Laboratory, John Innes Centre, Norwich Research Park, Colney, Norwich NR4 7UH, U.K
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71
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Affiliation(s)
- James B. Howard
- Department of Biochemistry, 435 Delaware Street, University of Minnesota, Minneapolis, Minnesota 55455, and Division of Chemistry and Chemical Engineering, 147-75CH, California Institute of Technology, Pasadena, California 91125
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72
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Richards RL. Reactions of small molecules at transition metal sites: studies relevant to nitrogenase, an organometallic enzyme. Coord Chem Rev 1996. [DOI: 10.1016/0010-8545(96)01186-1] [Citation(s) in RCA: 117] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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73
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Shestakov AF. Unique peculiarities of the structure of the Fe-Mo cofactor of nitrogenase favorable for multicenter coordination of a nitrogen molecule. Russ Chem Bull 1996. [DOI: 10.1007/bf01457757] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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74
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Demadis KD, Malinak SM, Coucouvanis D. Catalytic Reduction of Hydrazine to Ammonia with MoFe(3)S(4)-Polycarboxylate Clusters. Possible Relevance Regarding the Function of the Molybdenum-Coordinated Homocitrate in Nitrogenase. Inorg Chem 1996; 35:4038-4046. [PMID: 11666602 DOI: 10.1021/ic960098b] [Citation(s) in RCA: 98] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The catalytic function of the previously synthesized and characterized [(L)MoFe(3)S(4)Cl(3)](2)(-)(,3)(-) clusters (L = tetrachlorocatecholate, citrate, citramalate, methyliminodiacetate, nitrilotriacetate, thiodiglycolate) and of the [MoFe(3)S(4)Cl(3)(thiolactate)](2)(4)(-) and [(MoFe(3)S(4)Cl(4))(2)(&mgr;-oxalate)](4)(-) clusters in the reduction of N(2)H(4) to NH(3) is reported. In the catalytic reduction, which is carried out at ambient temperature and pressure, cobaltocene and 2,6-lutidinium chloride are supplied externally as electron and proton sources, respectively. In experiments where the N(2)H(4) to the [(L)MoFe(3)S(4)Cl(3)](n)()(-) catalyst ratio is 100:1, and over a period of 30 min, the reduction proceeds to 92% completion for L = citrate, 66% completion for L = citramalate, and 34% completion for L = tetrachlorocatecholate. The [Fe(4)S(4)Cl(4)](2)(-) cluster is totally inactive and gives only background ammonia measurements. Inhibition studies with PEt(3) and CO as inhibitors show a dramatic decrease in the catalytic efficiency. These results are consistent with results obtained previously in our laboratory and strongly suggest that N(2)H(4) activation and reduction occur at the Mo site of the [(L)MoFe(3)S(4)Cl(3)](2)(-)(, 3)(-) clusters. A possible pathway for the N(2)H(4) reduction on a single metal site (Mo) and a possible role for the carboxylate ligand are proposed. The possibility that the Mo-bound polycarboxylate ligand acts as a proton delivery "shuttle" during hydrazine reduction is considered.
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75
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Catalytic and stoichiometric multielectron reduction of hydrazine to ammonia and acetylene to ethylene with clusters that contain the MFe3S4 cores (MMo, V). Relevance to the function of nitrogenase. ACTA ACUST UNITED AC 1996. [DOI: 10.1016/1381-1169(95)00168-9] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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76
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George GN, Prince RC, Bare RE. Electron Paramagnetic Resonance Spectroscopy of the Iron-Molybdenum Cofactor of Clostridium pasteurianum Nitrogenase. Inorg Chem 1996; 35:434-438. [PMID: 11666225 DOI: 10.1021/ic950740m] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We report a computer simulation study of the electron paramagnetic resonance (EPR) spectral line shape of the iron-molybdenum cofactor of nitrogenase. The unusually broad and asymmetric line shape of the EPR spectrum can be interpreted in terms of a distribution of zero-field splitting parameters called D-strain. The best fit simulations were computed using D = 2.5 cm(-1) and E = 0.317 cm(-1) and distributions in D and E approximated by Gaussians of half-widths 0.446 cm(-1) and 0.108 cm(-1), respectively. The value of D estimated in the present work is smaller than previous estimates by others but consistent with the temperature dependence of the EPR spectrum. The large D-strain is most likely caused by an ensemble of nearly isoenergetic conformational states and should not be considered as being indicative of chemical inhomogeneity.
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Affiliation(s)
- Graham N. George
- Stanford Synchrotron Radiation Laboratory, Stanford University, SLAC MS 69, P.O. Box 4349, Stanford, California 94309, and Exxon Research and Engineering Company, Route 22 East, Annandale, New Jersey 08801
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Ferrence GM, Fanwick PE, Kubiak CP. A telluride capped trinuclear nickel cluster [Ni3(µ3-Te)2(µ-PPh2CH2PPh2)3]n+with four accessible redox states (n=–1, 0, 1, 2). Chem Commun (Camb) 1996. [DOI: 10.1039/cc9960001575] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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80
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81
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Abstract
Cleavage of the relatively inert dinitrogen (N(2)) molecule, with its extremely strong N identical withN triple bond, has represented a major challenge to the development of N(2) chemistry. This report describes the reductive cleavage of N(2) to two nitrido (N(3-)) ligands in its reaction with Mo(NRAr)(3), where R is C(CD(3))(2)CH(3) and Ar is 3,5-C(6)H(3)(CH(3))(2'), a synthetic three-coordinate molybdenum(III) complex of known structure. The formation of an intermediate complex was observed spectroscopically, and its conversion (with N identical withN bond cleavage) to the nitrido molybdenum(VI) product N identical withMo(NRAr)(3) followed first-order kinetics at 30 degrees C. It is proposed that the cleavage reaction proceeds by way of an intermediate complex in which N(2) bridges two molybdenum centers.
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Deeth RJ, Langford SA. Metal–dinitrogen σ- and π-bonding roles in [Fe(dmpe)2H(N2)]+, [Fe(depe)2(N2)] and trans-[V(dmpe)2(N2)2]–(dmpe = Me2PCH2CH2PMe2, depe = Et2PCH2CH2PEt2). ACTA ACUST UNITED AC 1995. [DOI: 10.1039/dt9950000001] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Plass W. Electronic structure of the iron-molybdenum and alternative cofactors of nitrogenases: a comparison and its consequences. ACTA ACUST UNITED AC 1994. [DOI: 10.1016/0166-1280(94)03766-e] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Abstract
Biological nitrogen fixation is catalyzed by the nitrogenase enzyme system which consists of two metalloproteins, the iron (Fe-) protein and the molybdenum-iron (MoFe-) protein. Together, these proteins mediate the ATP-dependent reduction of dinitrogen to ammonia. Recent crystallographic analyses of Fe-protein and MoFe-protein have revealed the polypeptide fold and the structure and organization of the unusual metal centers in nitrogenase. These structure provide a molecular framework for addressing the mechanism of the nitrogenase-catalyzed reaction. General features of the nitrogenase system, including conformational coupling of nucleotide hydrolysis, aspects of the cluster structures, and the general spatial organization of redox centers within the protein subunits, are relevant to a wide range of biochemical systems.
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Affiliation(s)
- J Kim
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena 91125
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Gailus H, Woitha G, Rehder D. Dinitrogenvanadates(–I): synthesis, reactions and conditions for their stability. ACTA ACUST UNITED AC 1994. [DOI: 10.1039/dt9940003471] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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