Iron clusters reductions

At the time this suggested that the activation of aconitase required reduction of the Fe-S cluster, rather than the addition of iron. This would relegate iron to the role of an efficient reductant of the Fe-S cluster. Also, while reduction of the cluster by sodium dithionite was immediate, development of full enzyme activity required minutes (41,42). This suggested that perhaps cluster reduction triggered a conformational change which led to activation. Fluorescence studies on the reduction and activation process of aconitase by Ramsay (43,44) supported this idea. Again Mossbauer spectroscopy provided the key to understand the fate of the added iron (39). 

Davydov, A., Davydov, R., Gr%oslund, A., Lipscomb, J. D., and Andersson, K. K., 1997, Radiolytic reduction of methane monooxygenase dinuclear iron cluster At 77K6EPR evidence for conformational change upon reduction or binding of component B to the diferric state, J. Biol. Chem. 272 702267026. 

The iron cluster [Fe4S4(SPh)4] catalyzes the reduction of nitroarenes to arylamines. " A less hydridic nucleophile [HFe(CO)4] has also found application as a selective reducing agent for nitroarenes." Although [HFe(CO)4]"] is known to reduce aldehydes, ketones and acid halides," in THF solvent with tri-fluoroacetic acid, it selectively reduces nitrobenzenes to anilines in the presence of aldehyde and acid halide groups. 

The model can be extended to predict the direction of adsorbate-induced shifts in cluster IP upon the chemisorption of other reactant molecules as well. To illustrate this, consider the chemisorption of ammonia. In this case the net charge donation is from a filled nonbonding orbital of NH3 to the metal cluster (metal-acceptor interaction), resulting in associative chemisorption of NH3 onto the cluster. In contrast to the situation for H2, adsorption of NH3 can be viewed as a reductive addition process with respect to the metal cluster, thus resulting in an increase in the Fermi level and a decrease in IP. This prediction is in excellent agreement with recent data for NH3 chemisorbed on iron clusters, which indicate that the IPs of the fully ammoniated (saturated) clusters are as much as 2 eV lower than those of the corresponding naked clusters. 

Whereas trinuclear iron clusters have been used in stoichiometric reduction of aromatic nitro compounds, the tetranuclear iron cluster Cp4Fe4(CO)4 can be used for the catalytic hydrogenation of nitrobenzene to aniline [Table IV (92,96,113-116)]. 

Bulk electrolyses are used to prepare one-electron reduction or oxidation products. If cyclic voltammetry (CV) reveals reversible redox, the bulk preparation of the reduced (or oxidized) product may be attained. The overall electrode process may be different in controlled-potential electrolysis and in CV because of the time factor (see below). The iron cluster, (h -CjHjFeCO), in nonaqueous electrolytes undergoes a four-membered electron-transfer CV series through three steps. The potentials measured (in CHjCN/O.l M [n-Bu N] [PFJ) are ... 

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