Development of a versatile synthesis method for trinuclear Co(iii), Rh(iii), and Ir(iii) dithiolene complexes, and their crystal structures and multi-step redox properties

Abstract

Triangular trinuclear Co(III), Rh(III), and Ir(III) dithiolene complexes, [[M₃(η⁵-C₅Me₅)₃(S₆C₆)] (M = Co, Rh, Ir), which have not been obtained by the trimerization of mononuclear complexes, were synthesized via a new synthetic route, that is, the reaction of benzenehexathiol and [(η⁵-C₅Me₅)Co(CO)I₂], [Rh(η⁵-C₅Me₅)Cl₂]₂ and [Ir(η⁵-C₅Me₅)Cl₂]₂, respectively, under basic conditions. Single crystal X-ray diffraction measurements were carried out and their crystal structures were determined. Electrochemical measurements revealed that the trinuclear complexes exhibit three-step one-electron redox reactions and form mixed valence complexes. Studies on the stabilities of their mixed valence states and the X-ray crystal structure analyses revealed that the through-bond internuclear electronic interaction and the aromaticity of central benzene ring decrease in the order of Co > Rh > Ir.