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

Abstract

[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: (NEt 4) 2[L 2Fe 2(μ-S) 2] with L Me 2C(C 4H 3N) 2 ( 1), Ph 2C(C 4H 3N) 2 ( 2), (CH 2) 5C(C 4H 3N) 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.