New insights into the chemistry of di- and trimetallic iron dithiolene derivatives. Structural, Mössbauer, magnetic, electrochemical and theoretical studies

Abstract

Reaction of Fe₃(CO)₁₂ with 1,2-dithiolene HSC₆H₂Cl₂SH affords a mixture of complexes [Fe₂(CO)₆(μ-SC₆H₂Cl₂S)] 1, [Fe₂(SC₆H₂Cl₂S)₄] 2 and [Fe₃(CO)₇(μ₃-SC₆H₂Cl₂S)₂] 3. In the course of the reaction the trimetallic cluster 3 is first formed and then converted into the known dinuclear compound 1 to afford finally the neutral diiron tetrakis(dithiolato) derivative 2. Compounds 2 and 3 have been studied by Mössbauer spectroscopy, X-ray crystallography and theoretical calculations. In compound 2 the metal atoms are in an intermediate-spin Fe^III state (S_Fe = 3/2) and each metal is bonded to a bridging dithiolene ligand and a non-bridging thienyl radical (S = 1/2). Magnetic measurements show a strong antiferromagnetic coupling in complex 2. Cyclic voltammetry experiments show that the mixed valence trinuclear cluster 3 undergoes a fully reversible one electron reduction. Additionally, compound 3 behaves as an electrocatalyst in the reduction process of protons to hydrogen.