Iron clusters nitroarenes

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 cluster Ru3(CO)i2 is known to react in the presence of bases to afford, under certain experimental conditions, [HRu3(CO)u] [42]. Since the corresponding iron cluster is known to react with nitrobenzene to yield an hydrido imido cluster [HFe3(CO)9(NPh)] , which can be protonated and afford small amounts of aniline [43], a catalytic cycle was proposed, and supported by some model reactions, for the ruthenium-catalysed reduction of nitroarenes by CO/H2O, which includes the intermediate formation of the trinuclear hydrido cluster [44-46]. However, one of us has recently shown that [HFe3(CO)n] and the corresponding imido complex play no role in the Fe3(CO)i2-promoted reduction of nitrobenzene [6, 47] and the proposal of an active role of [HRu3(CO)ii] appears to be questionable. 

Following the isolation of these complexes, all of the mechanistic studies on the carbonylation and reduction reactions of nitroarenes catalysed by Ru3(CO)i2, even in the presence of several promoters, have focused on the reactivity of these or related clusters [157-164]. Moreover, many studies have been also conducted on analogous osmium [165-172] and iron (see paragraph 6.6.) clusters, including insertion reactions of isocyanates, which yield potential intermediates in the carbonylation reaction (Insertion reaction of other cumulenes into the Ru-N bond will not be discussed here. However, see the paragraph of the synthesis of heterocycles later in this chapter). Although not all of the previously mentioned studies were intended to be a basis for a mechanistic understanding of the reactions here discussed, they still contain a lot of information on the possible transformations of amido or imido moieties on a trinuclear cluster. 

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See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ , ]

See also in sourсe #XX -- [ , ]

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