What is "iron-sulfur cluster"

n. (context biochemistry English) a unit comprising two or more iron atoms and bridging sulfur ligands in an iron-sulfur protein

Iron-sulfur clusters are ensembles of iron and sulfide centres. Fe-S clusters are most often discussed in the context of the biological role for iron-sulfur proteins. Many Fe-S clusters are known in the area of organometallic chemistry and as precursors to synthetic analogues of the biological clusters (see Figure).