Proton reduction using cyclopentadienyl Fe(II) (benzene-1,2-dithiolato) carbonyl complexes as electrocatalysts

Abstract The UV photolysis of cyclopentadienyl iron dicarbonyl dimer [CpFe(CO)2]2 and benzene-1,2-dithiol or 3,6-dichloro-1,2-benzenedithiol afforded dinuclear iron complexes [Cp2Fe2(CO)(bdt)(μ-CO)] (1) and [Cp2Fe2(CO)(Cl2-bdt)(μ-CO)] (2) respectively (bdt = benzene-1,2-dithiolato, Cl2-bdt = dichloro-1,2-benzenedithiolato). Further oxidation of the two complexes resulted in the release of CO and generated [CpFe(bdt)]2 (3) and [CpFe(Cl2-bdt)]2 (4). All four complexes were found to catalyse proton reduction at a similar overpotential and rate when trifluoroacetic acid (TFA) was used as a proton source. Both experimental and computational studies lent support to a mononuclear iron intermediate species carrying the CpFe(bdt) or CpFe(Cl2-bdt) moiety acting as the catalyst in the proton reduction process.