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Nitric oxide (NO), produced by nitrite reductases or nitric oxide synthases, performs vital roles in signaling and the immune response. Iron sulfur (FeS) clusters are known targets for NO induced degradation, serving as sensors to trigger cellular responses. However, this FeS reactivity is proposed as NO specific, with no demonstrated reactivity toward nitrite, a soluble NO storage molecule. We demonstrate that synthetic FeS clusters supported by various ligands undergo facile nitrosylation by nitrite in the presence of a reductant, evidencing the nitrite reductase reactivity for FeS clusters. Moreover, a mononitrosylated Fe4S4 cluster, [tempS3Fe4S4(NO)]2–, can be readily synthesized by this approach, enabling further investigation into the FeS cluster repair and decomposition under NO induced oxidative stress. 

Iron hydrides are proposed reactive intermediates for N2 and CO conversion in industrial and biological processes. Here, we report a reactivity study of a low-coordinate di(μ-hydrido)diiron(II) complex, Fe2(μ-H)2L, where L2– is a bis(β-diketiminate) cyclophane, with isocyanides, which have electronic structures related to N2 and CO. The reaction outcome is influenced by the isocyanide substituent, with 2,6-xylyl isocyanide leading to H2 loss, to form a bis(μ-1,1-isocyanide)diiron(I) complex, whereas all of the other tested isocyanides insert into the Fe–H bond to give (μ-1,2-iminoformyl) complexes. Steric bulk of the isocyanide substituent determines the extent of insertion (i.e., into one or both Fe–H–Fe units) with tert-butyl isocyanide reacting to yield the mono-(μ-1,2-iminoformyl)diiron(II) complex, exclusively, and isopropyl- and methyl isocyanides affording the bis(μ-1,2-iminoformyl)diiron(II) products. Treatment of Fe2(μ-1,2-CHNtBu)(μ-H)L with 2,6-xylyl isocyanide (or XylNC) yields Fe2(μ-XylNC)2L and tert-butylaldimine as one of the organic products.