Redox Non-Innocence of ortho-Benzoquinone Dioximate Dianion in Ligand Exchange on Ruthenium

A ruthenium complex bearing an o-benzoquinone dioximate dianion was isolated, and its ligand-based redox chemistry was clarified. The reaction of [Cp*RuCl2(NO)] (Cp*=eta(5)-C5Me5) with o-benzoquinone dioxime ((LH2)-H-red) in the presence of a base afforded a dioximato ruthenium complex [Cp*Ru(NO)(L-red)] (1). Upon treatment with an iodonium salt, 1 underwent two-electron oxidation of L-red along with ligand exchange to give the o-dinitrosobenzene (L-ox) iodido complex [Cp*RuI(L-ox)] (2). H-1 NMR, IR, X-ray analyses, and DFT calculations revealed that the L-red ligand in 1 was oxidized and aromatized during the ligand substitution. The L-ox ligand in 2 was reduced by benzensulfohydroxamic acid with the aid of a base, leading to regeneration of the L-red nitrosyl complex 1. The non-innocence of L-red/ox in the ligand exchange would lead to level the energy profile of redox processes including catalysis.

Automated summary

A ruthenium complex with an o-benzoquinone dioximate dianion was isolated, and the redox chemistry of its ligand was elucidated. The complex underwent ligand exchange and oxidation reactions, and the reduced ligand was regenerated through a catalytic reduction process with the aid of a base.