The paper documents redox-triggered C–C coupling of acyclic N,N′-bis­(2-pyridylmethylene)­ethylenediamine (BPE) to yield 2,3-bis­(2-pyridyl)­pyrazine (DPP) upon coordination to an electron-rich {Ru­(acac)2} (acac = acetylacetonate) unit. This led to DPP-bridged [{Ru­(acac)2}2(DPP)]0/+ (2 and [2]­ClO4) along with the unperturbed BPE-bridged [{Ru­(acac)2}2(BPE)] (1). On the contrary, electron-poor {Ru­(Cl)­(H)­(CO)­(PPh3)3} yielded BPE-bridged [3]­(ClO4)2 as an exclusive product. Synergistic metal (Ru)–ligand (BPE) redox participation toward chemical noninnocence of the Schiff base ligand and DPP-mediated electronic communication in RuIIRuIII-derived [2]­ClO4 are addressed.

The unexplored 'actor' behavior of redox-active bis(aldimine) congener, p-phenylene-bis(picoline)aldimine (L1), towards dioxygen activation and subsequent functionalization of its backbone was demonstrated on coordination with {Ru(acac) 2 } (acac = acetylacetonate). Reaction under aerobic condition led to the one-pot generation of dinuclear complexes with unperturbed L1, imino-carboxamido (L2 À ), and bis(carboxamido) (L3 2À )-bridged isovalent {Ru II (μ-L1)Ru II }, 1/ {Ru III (μ-L3 2À )Ru III }, 3 and mixed-valent {Ru II (μ-L2 À )Ru III }, 2.Authentication of the complexes along with the redox noninnocence behavior of their bridge have been validated through structure, spectroelectrochemistry and DFT calculations. Kinetic and isotope labelling experiments together with DFT analyzed transition states justified the consideration of redox shuttling at metal/L1 interface for 3 O 2 activation despite of the closed shell configuration of 1 (S = 0) to give carboxamido derived 2/3. Synergistic effort of redox-active metal and ligand is used as a protagonist in numerous biological [1] and catalytic [2] processes. [3] Complex with ligand-centered redox event facilitates shuttling of electron at the metal-ligand interface (M n L p $ M n + 1 L pÀ 1 ) through the effective overlapping of their suitably oriented frontier molecular orbitals and that results in valence tautomerism [4,5] or dynamic resonance. [4,6] This in effect promotes diverse reactivity profile of such ligand systems to manifest their "actor" behavior. [7] In line with this, the present article highlights a unique example of ligand-centered oxygenation for the stoichiometric conversion of bis(aldimine) to bis(carboxamido) on diruthenium platform based on dynamic resonance induced dioxygen activation (Scheme 1). Although metal ion mediated functionalization of imine to carboxamido in presence of exogenous reagents such as H 2 O, H 2 O 2 , acid, Ce IV , [8] are well explored, only a few reports by Manuel and Rohde, [9a] de Bruin and co-workers [9b] (M = Ni, Ir, Rh, Scheme 1) have demonstrated oxygen atom transfer from molecular oxygen to the metal bound imine backbone, which led to an occasional scenario of carboxamido formation.In this context, the present work delineates stepwise oxygenation of the two aldimine functions of p-phenylene-[a