Iron–sulphur dimers with benzimidazolate–thiolate, benzimidazolate–phenolate, or bis(benzimidazolate) terminal chelating ligands

[Fe2S2L2]2– complexes co-ordinated by the mixed-donor N–S, N–O, or N–N ligands L1–L4 are characterised by electronic and n.m.r. spectroscopy and shown to undergo one-electron reduction to the corresponding trianions with e.s.r. spectra exhibiting a range of g-tensor values which are compared with those for [2Fe–2S]+ proteins of the Rieske type.