Journal ArticleDOI
Chemical evolution of a nitrogenase model. VII. Reduction of nitrogen
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The current molybdothiol model systems were expanded to include ferredoxin-type complexes as electron-transfer catalysts, which provided new catalytically active systems containing molybdenum, iron, labile sulfide, and RSH components in proportions similarmore to that observed in native nitrogenase.Abstract:
Nitrogenase model systems composed of molybdate and thiol ligands such as L(+)-cysteine reduce molecular nitrogen to ammonia slowly in the presence of NaBH/sub 4/ as the reducing agent. In the presence of substrate amounts of ATP, the reduction of nitrogen is significantly stimulated but leads to the accumulation of diimide in the reaction solutions. The diimide decomposes or disproportionates to nitrogen, hydrogen, and hydrazine and is not reduced as such. The ammonia produced in all reactions arises primarily from the reduction of hydrazine. These observations were confirmed by independent experiments with diimide generated by the decomposition of azodicarboxylate and with hydrazine. Diimide is not a substrate for molybdothiol catalyst systems, while hydrazine is catalytically reduced to ammonia. Molybdothiol catalysts promote D/sub 2/-- H/ sup +/ exchange most efficiently in the presence of nitrogen as the substrate; they thus parallel nitrogenase also in this respect. The D/sub 2/-H/sup +/ exchange reaction is prssumably linked to the formation and decomposition of diimide in both the nitrogerase enzyme and its models. The current molybdothiol model systems were furthermore expanded to include ferredoxin-type complexes as electron-transfer catalysts. This provided new catalytically active systems containing molybdenum, iron, labile sulfide, and RSH components in proportions similarmore » to that observed in native nitrogenase. The new model systems catalyze the reduction of, e.g., acetylene efficiently even with S/sub 2/O/sub 4/ as the reducing agent and thus duplicate nitrogenase in yet another important respect. (12 tables, 6 figures) (auth)« lessread more
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Developing more sustainable processes for ammonia synthesis
TL;DR: In this article, a transition metal-dinitrogen-bridged dimolybdenum complex bearing two PNP-type pincer ligands was used as a catalyst for the conversion of molecular dinitrogen into ammonia or ammonia equivalent, silylamine.
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Metal–Sulfur Compounds in N2 Reduction and Nitrogenase-Related Chemistry
Kazuki Tanifuji,Yasuhiro Ohki +1 more
TL;DR: The aims of this review are to compile a collection of studies performed at atomic to mesoscopic scales and to present potential opportunities for elucidating the roles of metal and sulfur atoms in the biological N2 fixation that might be helpful for the development of functional materials.
Journal ArticleDOI
Catalytic Dinitrogen Fixation to Form Ammonia at Ambient Reaction Conditions Using Transition Metal-Dinitrogen Complexes
TL;DR: This paper presents recent progress in catalytic transformation of molecular dinitrogen into ammonia or its equivalents, such as silylamine, especially using transition metal-dinitrogen complexes under ambient reaction conditions.
Journal ArticleDOI
Biologically related iron-sulfur clusters as reaction centers. Reduction of acetylene to ethylene in systems based on [Fe4S4(SR)4]3-.
TL;DR: The results demonstrate that biologically related, reduced Fe4S4 clusters can effect reduction of at least one Fe-S enzyme substrate, and raise the general possibility of substrate transformation with such clusters as reaction sites in biological systems.