Synthesis, characterization and electrochemical properties of phosphine-disubstituted diiron bis(monoselenolate) carbonyls

Abstract

The properties of diiron dithiolates/diselenolates have been exhaustively studied, the substituted bis(monoselenolate) carbonyls are rarely described. In order to enrich the chemistry of diiron diselenolate compounds and synthesize new hydrogen evolution catalysts, a series of monosubstituted diiron bis(monoselenolate) carbonyls [Fe2(µ-SeCH2Ph)2(CO)5L] (L = PPh3, 1a; PPh2Me, 1b; PPhMe2, 1c; PMe3, 1d), and two disubstituted diiron bis(monoselenolate) carbonyls [Fe2(µ-SeCH2Ph)2(CO)4L2] (L = PPh3, 2a; PPh2Me, 2b) have been prepared. That is, treatment of [Fe2(μ-SeCH2Ph)2(CO)6](1) with 1 equivalent of PR3 ligand in the presence of Me3NO·2H2O afforded the 1a-1d in 47–63% yields. Alternately, treatment of [Fe2(μ-SeCH2Ph)2(CO)6] (1) with 2 equivalents of PPh3 and PPh2Me under efficient one-pot UV-irradiation produced 2a and 2b in moderate yields. 1a-1d exist as two isomers, while only syn-isomer are found in 2a and 2b. All the new compounds were characterized by elemental analysis, IR, NMR spectroscopy and X-ray crystallography. In addition, the electrochemical and electrocatalytic properties of these models were studied by cyclic voltammetry (CV) in MeCN.