Relatively stable N-ligated [2Fe2S]2+ clusters with dipyrromethane capping ligands

[2Fe2S] clusters with terminal N-ligation (His, Arg) and unique functions are increasingly recognized in biological systems. In this work three new [2Fe2S] clusters 1-3 with different 1,1′-dipyrrolmethane derivatives as chelating terminal ligands have been prepared and fully characterized, including by X-ray crystallography: (NEt4)2[L2Fe2(μ-S)2] with LMe2C(C4H3N)2 (1), Ph2C(C4H3N)2 (2), (CH2)5C(C4H3N)2 (3). These systems represent rare examples of synthetic [2Fe2S] complexes with N-donor capping ligands. While geometric parameters as well as spectroscopic and electrochemical characteristics of the new complexes are as anticipated, the chelating nature of the terminal ligands in 1-3 imparts a relatively high stability that will be advantageous for reactivity studies of the [2Fe2S] core.