Reversible Bond Formation and Cleavage of the Oxo Bridge of [Ru2(μ‐O)(dioxolene)2(btpyxa)]3+ [btpyxa = 2,7‐Di‐tert‐butyl‐9,9‐dimethyl‐4,5‐bis(2,2′:6′,2′′‐terpyrid‐4′‐yl)xanthene] Driven by a Three‐Electron Redox Reaction

The bis(chlororuthenium) complex [Ru 2 Cl 2 (3,6-tBu 2 sq) 2 -(btpyxa)](PF 6 ) 2 [1](PF 6 ) 2 [3,6-tBu 2 sq = 3,6-di-tert-butyl-1,2-benzosemiquinone; btpyxa = 2,7-di-tert-butyl-9,9-dimethyl-4,5-bis(2,2':6',2"-terpyrid-4'-yl)xanthene] and the oxo-bridged diruthenium complex [Ru 2 (μ-O)(3,6-tBu 2 sq) 2 -(btpyxa)](PF 6 ) 3 [2](PF 6 ) 3 were synthesized, and the redox behavior of these complexes, which contain a non-innocent dioxolene ligand, was investigated by electrochemical and electrospectrochemical methods. Dicationic [1] 2 + undergoes two successive metal-centered one-electron and a simultaneous two-electron ligand-based redox reaction at E 1 / 2 = +0.13 and +0.09 and E 1 / 2 = -0.75 V (vs. SCE), respectively, in CH 2 Cl 2 . The UV/Vis/NIR spectrum of tricationic [2] 3 + shows an intervalence-transition (IT) band at 1333 nm (e = 1.52 × 10 4 M - 1 cm - 1 ) in a near-IR region together with two CT bands at 766 (e = 2.21 × 10 4 M - 1 cm - 1 ) and 586 nm (e = 1.13×10 4 M - 1 cm - 1 ) in CH 2 Cl 2 . The mixed-valence complex of [2] 3 + with an Ru I V -O-Ru I I I core is reversibly oxidized and reduced to the Ru I V -Ru I V and Ru I I I -Ru I I I oxidation states at E 1 / 2 = +0.63 and -0.01 V, respectively, in CH 2 Cl 2 . On the other hand, three-electron reduction of [2](PF 6 ) 3 is accompanied by the cleavage of the Ru-O-Ru bond at E p = +0.02 V to give [(Ru(OMe)(3,5-tBu 2 sq))(Ru(OH 2 )(3,5-tBu 2 sq))-(btpyxa)] + in MeOH.