Synthesis, characterization, and electrochemical properties of diiron bis(monotellurolate) carbonyls related to [FeFe]-hydrogenases

Abstract

To explore the study of mimicking behaviors of H-cluster by Fe/Te compounds, a series of structural and functional models of diiron bis(monotellurolate) carbonyls have been prepared. Thus, treatment of diaryl ditelluride (ArTe)2 with Fe3(CO)12 at reflux temperature give parent compounds Fe2(μ-TeAr)2(CO)6 (Ar = C6H51, C6H4-4-F, 2). Further reactions of 1 and 2 with 1 equiv of monophosphines afford the corresponding monophosphine-substituted compounds Fe2(μ-TeAr)2(CO)5L (Ar = C6H5, L = PPh3, 3; Ar = C6H4-4-F, L = PPh3; 4, Ar = C6H5, L = PMe3, 5; Ar = C6H4-4-F, L = PMe3, 6) in 38–60% yields. Of particular interest here, both anti- and syn-isomers for 1–4 are isolated as solid states using the TLC method. While only anti-forms are found in 5 and 6, the PMe3 ligand lies on the apical position in 5, but prefers the basal position in 6. The diphosphine-bridged compounds Fe2(μ-TeAr)2(CO)4(dppm) (Ar = C6H5, 7; Ar = C6H4-4-F, 8) can be prepared by treatment of 1 and 2 with 1 equiv of bis(diphenylphosphino)methane (dppm) in refluxing xylene in 58% and 64% yields. All the compounds are characterized by elemental analysis, FT-IR, NMR spectroscopy, and particularly for 1-anti/syn, 2-anti/syn, 3-anti/syn, 4-anti and 5–8 by X-ray diffraction analyses. In addition, the electrochemical and electrocatalytic properties of 1–8 are studied by cyclic voltammetry (CV) in MeCN, indicating that they are all found to be catalysts for H2 production in the presence of acetic acid (HOAc) under electrochemical conditions.