ChemInform Abstract: Nitrosyl Complexes of Iron‐Sulfur Clusters

Abstract

Publisher Summary This chapter discusses nitrosyl complexes of iron-sulfur clusters. The recent upsurge of interest in iron-sulfur-nitrosyl complexes has been stimulated in part by the reported isolation of [ Fe2(SMe)2(NO)4] from natural sources, by the obvious resemblances between these complexes and the naturally occurring [2Fe–2S] and [4Fe–4S] clusters of iron-sulfur proteins, and by the connections between tetrairon-sulfur-nitrosyls and cubane-type clusters. Salts containing the anions [ Fe2S2(NO)4]2– and [Fe4S3(NO)7]– are often called, from their colors, Roussin's red and black salts, respectively. Similarly, the organic derivatives [Fe2(SR)2(NO)4] are often called esters of Roussin's red salt. The number of iron-selenium-nitrosyl complexes is substantially smaller than the iron-sulfur-nitrosyl species, and there are a number of differences between the sulfur systems and their analogs containing selenium or tellurium. For selenium it is convenient to divide the complexes into three classes, dependent upon the stoichiometry of the metal-chalcogen framework. A variety of routes have been employed for the synthesis of heterometallic clusters containing Fe(NO)S fragments, and examples of such systems have been described. The diamagnetic behavior of the diiron and tetrairon complexes, despite the presence of formally d7 and/or d9 iron centers, indicates very strong coupling between the individual paramagnetic centers.