Catalytic behavior of a polynuclear Mg-Mo complex and nitrogenase active site (FeMoco) isolated from the enzyme in reactions with C2H2, N2, and CO: A comparative study |
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Authors: | N V Bardina T A Bazhenova G N Petrova A K Shilova A E Shilov |
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Institution: | (1) Institute of Problems of Chemical Physics, Russian Academy of Sciences, 142432 Chernogolovka, Moscow Region, Russian Federation |
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Abstract: | In order to identify common and distinctive features in the catalytic behavior of natural and artificial nitrogen-fixation
clusters, the kinetics of the catalytic reduction of C2H2 in the presence of Mg-Mo-cluster (1) was investigated and compared with the kinetics of acetylene reduction catalyzed by the cluster FeMoco (2) isolated from the enzyme nitrogenase we studied previously. The reactions were conducted in the presence of Zn/Hg and Eu/Hg
as reducing agents and PhSH and C6F5SH as proton donors, i.e., under the same conditions as had been used in the case of 2. Both polynuclear Mg-Mo-complex and the europium amalgam-reduced FeMoco have multiple interdependent binding sites for substrates
and/or inhibitors. Carbon monoxide inhibits the acetylene reduction much less efficiently in systems with cluster 1 than in systems with cluster 2, although the type of inhibition is mixed in both systems: CO binds to multiple sites of the cluster and affects both C2H2 complexation to the reduced cluster and decomposition of the catalyst-substrate complex to give the products. Unlike isolated
FeMoco, the Mg-Mo-cluster efficiently catalyzes the reduction of molecular nitrogen. The reaction is greatly inhibited by
acetylene, while no inhibiting effect of N2 is observed in acetylene reduction, as was found earlier for a system with the natural cluster as the catalyst.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 766–774, May, 2006. |
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Keywords: | biomimetics biological nitrogen fixation metal complex catalysis metal cluster active site structural and functional models mechanism nitrogenase acetylene reduction |
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