A mono-oxo-bridged binuclear iron(iii) complex with a Fe–O–Fe angle of 180.0° and its catalytic activity for hydrogen evolution

Abstract

There are potential applications for binuclear oxo-bridged iron complexes in biological processes, catalysts, and magnetic materials, and the design of new bridged-iron complexes is important. A new mono-oxo-bridged binuclear iron(III) complex, [(H₂O)(bpc)Fe–O–Fe(bpc)(H₂O)], is designed and provided by the reaction of FeCl₃ with 1,2-bis(pyridine-2-carboxamido)-4,5-dichlorobenzene) (H₂bpc) in our group. Structural investigations show that two ions are connected with a Fe–O–Fe angle of 180.0°, so it is a novel linear mono-oxo-bridged iron complex. Magnetic studies indicate that the iron(III) ions are in low spin (ls) states. Electrochemical investigations exhibit that [(H₂O)(bpc)Fe–O–Fe(bpc)(H₂O)] has Fe^IV/III, Fe^III/II, and Fe^II/I couples at 0.689, −0.476, and −2.065 V versus Ag/AgNO₃, respectively, and can electro-catalyze hydrogen evolution from acetic acid with a rate constant of 7561.95 M⁻¹ s⁻¹.