Synthesis, characterization and electrochemical properties of two isomers of diiron diselenolato complexes and a new pathway to the μ4-Se twin cluster

Abstract

Two isomers of diiron diselenolato complexes (ea)-(μ-SeC6H4-4-tBu)2Fe2(CO)6 (1), (ee)-(μ-SeC6H4-4-tBu)2Fe2(CO)6 (2) have been synthesized by treatment of (p-tBuC6H4Se)2 with Fe3(CO)12 at ambient temperature in 2 h. Moreover, a tetranuclear cluster complex [(μ-SeC6H4-4-tBu)Fe2(CO)6]2(μ4-Se) (3) was isolated by this simple and convenient way in 14% yield. All the three complexes were characterized by elemental analysis, FT-IR, NMR (1H, 13C) spectroscopy, as well as by X-ray diffraction analyses. Crystal structures reveal that complex 1 crystallizes in a chiral space group P4 (3), and the diselenolate substituents are axial-equatorial. For complex 2, both of the PhBu-t groups attached to their Se atoms by equatorial bonds. The structure of complex 3 consists of two [(μ-C6H4-4-tBu)Fe2(CO)6] units bridged by a pseudotetrahedral Se atom. Furthermore, the electrochemical properties for 1–3 were investigated by cyclic voltammetry. The results indicated that all the complexes could be used as electrocatalysts for reduction proton to hydrogen in the presence of HOAc in MeCN solution.