Diiron carbonyl complexes possessing a {Fe(ii)Fe(ii)} core: synthesis, characterisation, and electrochemical investigation

Abstract

Two diferrous complexes, [Fe₂(μ-SCH₂CH₃)₃(CO)₅I] and [Fe₂(μ-SCH₂CH₂CH₃)₃(CO)₅I] were synthesised via reaction of a monoiron carbonyl precursor, [Fe(CO)₄I₂], with ethanethiolate and propanethiolate, respectively. The complexes were fully characterised using spectroscopic techniques, for instance, FTIR and NMR. Their crystal structures were determined using single crystal diffraction analysis. Electrochemical reduction of these complexes are temperature-dependent. At room temperature, the diferrous complexes undergo one-electron reduction. The reduction-initiated cleavage of one bound thiolate and one iodide as a radical, takes the oxidation states of the diiron core from {Fe(I)Fe(II)} to {Fe(I)Fe(I)}. This reduction-initiated transformation can be suppressed by lowering the temperature to 195 K, further reduction of the monoanion was observed at a potential very close to that of the first reduction, which is analogous to the mechanism observed for diiron complexes with a core of {Fe(I)Fe(I)}.