Chemical evolution of a nitrogenase model. VII. Reduction of nitrogen

Schrauzer, G. N.; Kiefer, Gebhard; Tano, Kazuo; Doemeny, P. A.

doi:10.1021/ja00810a001

Cited by 57 publications

(9 citation statements)

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“…In the absence of molybdenum, no ammonia is produced. Although specific stimulation by ATP is claimed, acids may produce the same effect (Schrauzer et al 1974;K hrushch et al 1974). Although no intermediates have been definitely characterized, the involvement of diazene has been proposed.…”

Section: -Red U CI N G Syst Em S In Protic Mediamentioning

confidence: 99%

New, man-made N ₂ -fixing systems

Newton

1987

Phil. Trans. R. Soc. Lond. B

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The major inputs of fixed N into the global nitrogen cycle are assessed and compared as indicators of both the need for and the likely basis of new, complementary, man-made N2-fixing processes. The development, since 1964, of the purely chemical, highly reactive systems for the reduction of N2, including those driven electro- and photochemically, is traced, along with the parallel efforts to synthesize metal-N2 complexes (the first step in any likely fixation process) and subsequently protonate them to produce hydrazine or ammonia. These experimental approaches are convergent. Successful cycling or catalysing of some of these N2-binding systems has been achieved. The advantages and limitations of the more successful systems are noted. Approaches to this problem via direct modelling of the nitrogenase active site are outlined, as is the one successful use of such complexes in achieving N2 reduction. This wealth of effort on the reductive approaches contrasts vividly with the almost complete absence of research on N2 oxidation. Currently, only a re-evaluation of the arc discharge process is continuing. Finally, the author's studies of the extruded molybdenum-containing prosthetic group of nitrogenase, the enzymic N2-reducing site, are described in relation to future N2-fixing systems.

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Section: -Red U CI N G Syst Em S In Protic Mediamentioning

confidence: 99%

New, man-made N ₂ -fixing systems

Newton

1987

Phil. Trans. R. Soc. Lond. B

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“…15 In the catalytic reduction of acetylene with Mo(NMe2)4, Mo-Mo multiple bond formation is expected. Thus, we examined how aggregation of a molybdenum complex affects catalytic activity by using a well-defined binuclear molybdenum complex, Moz(NMe2) 6 , as the catalyst. The results of acetylene reduction are shown in Table I and Figure 2.…”

Section: Preparation Of Catalystmentioning

confidence: 99%

Electron Transfer Reduction of Acetylene by Catalysis of Partially p-Mercaptomethyl Substituted Polystyrene–Molybdenum(IV) Complexes in Protic Solvent

Oguni

Shimazu

Iwamoto

et al. 1981

Polym J

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ABSTRACT:Molybdenum(IV) complexes supported on partially p-mercaptomethyl substituted cross-linked polystyrene were prepared. A binary system of the above molybdenum complexes and ferredoxin model compound, [Fe4 S4 (SPh)4 ]>-, has excellent catalytic activity for the reduction of acetylene, compared to the corresponding unsupported molybdenum complexes. The reduction and reductive cleavage of dinitrogen were also investigated as a nitrogenase model reaction.KEY WORDS Molybdenum(IV) Complex I Reduction of Acetylene Reduction of Dinitrogen I Catalysis of Polymer-Metal Complex IThe MoFe protein components of Clostridium pasteurianum 1 and Azotobacter vinelandii (Az. V) 2 nitrogenase and the FeMo cofactor (FeMo-co) 2 from Az. V were isolated; their K-edge X-ray absorption fine structure (EXAFS) analyses indicated that the molybdenum is coordinated by three or four organic and inorganic sulfides. The FeMoco has ca. 8% activity of native nitrogenase for the selective reduction of acetylene to ethylene with NaBH4 . 3 In an attempt to find a functional enzyme model, the ,u-dioxodi( oxomolybdenum)(V) complex coordinated by L-cysteine ligand, [Mo 2 0 4 (cys) 2 f-, was examined as a component of catalyst in nitrogenase model reaction for the reduction of acetylene and dinitrogen. 4 -6 Recently, an oxomolybdenum complex supported on insulin was found to have catalytic activity for the reductive cleavage of dinitrogen.7 The activity of this polypeptide-Mo complex was reported to be definitely higher than that observed for the Mo complexes of cysteine or other simple organic thiols. In our previous studies, 8 we have found that L-cysteine-containing copolypeptide-Mo(V) complexes had a higher catalytic activity than the corresponding non-supported Mo(V) complexes for the reduction of phenylacetylene and azobenzene. This high activity of polypeptide-Mo complexes was tentatively concluded as a result of preventing deactivation by the aggregation of a reduced catalytically active molybdenum species. Similar effect is significant for catalysis by Mo complexes supported on crosslinked polystyrene. This report deals with the catalytic reduction of acetylene with NaBH 4 by a binary system of Mo(IV) complexes of partially pmercaptomethyl substituted polystyrene and ferredoxin model compound, [Fe 4 S 4 (SPh) 4 f-.Reduction of dinitrogen was also examined using a catalyst system best suited for the acetylene reduction. EXPERIMENTAL InstrumentationVisible and UV spectra were taken with a JASCO-UVIDEC 5A spectrometer at room temperature. The identification and quantitative determination of the products in the reduction of acetylene were made by a Y anaco gas chromatograph model GSO equipped with Porapak N as column packing material at 40-160°. NMR spectra were taken with a Varian XL-100.

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“…Most suggestions are too vague to serve as a working hypothesis and more definite models for ATP action are required. In this context, it is of interest that molybdothiolborohydride complexes show favorable catalytic activity in the presence of ATP (184,185), albeit the mechanism of ATP is also obscure in these cases (but see Section VII)…”

Section: Jones and Burrismentioning

confidence: 99%

“…A single molybdenum site with side-on bonding of dinitrogen is the basis for a proposed mechanism of molybdothiol complexes which show many essential features of the enzyme (184,228). The reactive species is thought to be a monomeric cysteine Mo(IV) complex with two cis coordination positions (228):…”

Section: Reaction Modelsmentioning

confidence: 99%

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The molecular basis of biological dinitrogen fixation

Zumft

Structure and Bonding

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Chemical evolution of a nitrogenase model. VII. Reduction of nitrogen

Cited by 57 publications

References 1 publication

New, man-made N ₂ -fixing systems

New, man-made N ₂ -fixing systems

Electron Transfer Reduction of Acetylene by Catalysis of Partially p-Mercaptomethyl Substituted Polystyrene–Molybdenum(IV) Complexes in Protic Solvent

The molecular basis of biological dinitrogen fixation

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Chemical evolution of a nitrogenase model. VII. Reduction of nitrogen

Cited by 57 publications

References 1 publication

New, man-made N 2 -fixing systems

New, man-made N 2 -fixing systems

Electron Transfer Reduction of Acetylene by Catalysis of Partially p-Mercaptomethyl Substituted Polystyrene–Molybdenum(IV) Complexes in Protic Solvent

The molecular basis of biological dinitrogen fixation

Contact Info

Product

Resources

About

New, man-made N ₂ -fixing systems

New, man-made N ₂ -fixing systems