Bidentate phosphine ligand based Fe2S2-containing macromolecules: synthesis, characterization, and catalytic electrochemical hydrogen production

The reaction of Fe2(CO)6(mu-SCH2)2NCH2CH2N(mu-SCH2)2Fe2(CO)6] (1) with 1,2-bis(diphenylphosphino)ethane in the presence of Me3NO.2H2O affords two structurally different metallomacromolecules: a dimer of the type {Fe2(CO)5(mu-SCH2)2NCH2CH2N(mu-SCH2)2Fe2(CO)5}(Ph2PCH2)2] (2) and a tetramer species containing eight iron centers with an overall formula of {Fe2(CO)6(mu-SCH2)2NCH2CH2N(mu-SCH2)2Fe2(CO)5}2(Ph2PCH2)2] (3). Their structures have been determined by X-ray crystallography, showing one macrocyclic complex (2) and one linear complex (3). Electrochemical hydrogen evolution catalyzed by these two complexes with ca. 80-90 single-run turnovers is observed, indicating good potential as catalysts for future applications.