Synthesis, structure and redox properties of (μ-oxo)bis(μ-carboxylato)diruthenium(III) complexes containing three different terminal ligands

Abstract

Blue coloured, unstable, essentially diamagnetic and non-electrolytic diruthenium(III) complexes of the formation [Ru₂O(O₂CR)₄(en)₂(PPh₃)₂] were prepared by reacting [Ru₂O(O₂CR)₄(PPh₃)₂] with 1,2-diaminoethane (en) in CH₂Cl₂ (R = C₆H₄-p-X; X = H, Me and OMe). The molecular structure of the complexes is proposed as [{(η1-O₂CR)(η1-en)(PPH₃)Ru}₂(μ-O)(μ-O₂CR)₂] based on the 1H NMR spectral data. The electronic spectra of the complexes display a band near 569 nm with a shoulder at 630 nm. In CH₂Cl₂-0.1 M [Bun₄ⁿN]ClO₄, the complexes exhibit redox couples Ru₂^III,III/Ru₂^III,IV and Ru₂^III,IV/Ru₂^IV,IV near 0.1 and 1.2 V (vs SCE), respectively. The potentials are the lowest among diruthenium(III) complexes with a similar core structure.