Triiron clusters derived from dinuclear complexes related to the active site of [Fe–Fe] hydrogenases: steric effect of the dithiolate bridge on redox properties, a DFT analysis

Abstract

A series of triiron clusters [Fe₃(CO)₅(κ²-dppe)(μ-pdt^R₂)(μ-pdt)] featuring different combinations of dithiolate bridges have been prepared by using dinuclear and mononuclear precursors, [Fe₂(CO)₆(μ-xdt)] (xdt = pdt, pdt^Et₂, pdt^Bn₂, adt^Bn) and [Fe(CO)₂(κ²-dppe)(κ²-pdt)]. Novel triiron compounds, featuring sterically crowded dithiolate bridges (pdt^Et₂, pdt^Bn₂), were spectroscopically and structurally characterized. Their protonation and redox behaviours are discussed. The effect of the dithiolate bridges on the electrochemical properties (oxidation and reduction) of the complexes [Fe₃(CO)₅(κ²-dppe)(μ-xdt)(μ-pdt)] has been examined by cyclic voltammetry and rationalized by DFT calculations. Studies on the protonation of these species and their proton reduction behaviour were considered.