Mono- and di-substituted [FeFe]-hydrogenase H-cluster mimics bearing the 3,4-dimercaptobenzaldehyde bridge moiety: Insight into synthesis, characterization and electrochemical investigations

This report describes the synthesis and characterization of [FeFe]-hydrogenase mimic, namely [Fe-2(CO)(6){mu-bdtf}] (2, bdtf = 3,4-dimercaptobenzaldehyde) obtained from the reaction of 3,4-dimercaptobenzaldehyde with Fe-3(CO)(12). Moreover, treatment of complex 2 with PPh3 ligand yielded both mono-and disubstituted complexes [Fe-2(CO)(5)PPh3{mu-bdtf}] (3), [Fe-2(CO)(4)(PPh3)(2){mu-bdtf}] (4), while in the case of P(OMe)(3) ligand afforded only the disubstituted complex [Fe-2(CO)(4)(P(OMe)(3))(2){mu-bdtf}] (5). The molecular structures of complexes 2-5 were confirmed by X-ray diffraction analysis. Furthermore, the influence of the substituent on the benzene ring as well as at the iron center on the electrochemistry and catalysis of these mimics toward proton reduction have been evaluated by cyclic voltammetry. All complexes show their potentials toward hydrogen formation in the presence of weak acid, such as acetic acid (AcOH).

Automated summary

This report presents the synthesis and characterization of a mimic of [FeFe]-hydrogenase, named [Fe-2(CO)(6){μ-bdtf}] (2, bdtf = 3,4-dimercaptobenzaldehyde), obtained from the reaction between 3,4-dimercaptobenzaldehyde and Fe-3(CO)(12). Different ligands, such as PPh3 and P(OMe)(3), were used to modify complex 2, resulting in mono- and disubstituted complexes [Fe-2(CO)(5)PPh3{μ-bdtf}] (3), [Fe-2(CO)(4)(PPh3)(2){μ-bdtf}] (4), and [Fe-2(CO)(4)(P(OMe)(3))(2){μ-bdtf}] (5). The structures of complexes 2-5 were determined by X-ray diffraction analysis. The electrochemistry and catalytic activity of these mimics towards proton reduction were evaluated by cyclic voltammetry, with all complexes showing potential for hydrogen formation in the presence of weak acid, such as acetic acid (AcOH).