Monoanionic three-atom bridge ligand

The monoanion [Fe4Ss(NO)7] was prepared by Roussin in 1858 and its X-ray structure has been solved about twenty years ago. As illustrated in Figure la, it is constituted by a flattened tetrahedron of iron atoms, three faces of which are capped by triply-bridging sulfur atoms. Each one of the three basal irons binds two nitrosyl groups, whereas the apical iron bears only one nitrosyl ligand. 

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