Synthesis, electronic structure and redox properties of the diruthenium sandwich complexes [Cp*Ru(μ-C₁₀H₈)RuCp*]^x (x = 0,1+; Cp* = C₅Me₅; C₁₀H₈ = naphthalene)

The dinuclear ruthenium complex [Cp*Ru(μ-C₁₀H₈)RuCp*] (1; Cp* = η⁵-C₅Me₅) was prepared by reduction of the cationic precursor [Cp*Ru(η⁶-C₁₀H₈)]PF₆ with KC₈. Diamagnetic 1 has a symmetric molecular structure with an anti-facial configuration of the Cp*Ru moieties coordinating to naphthalene. Density Functional Theory (DFT) studies showed an electronic structure similar to that of the analogous diiron complex [Cp*Fe(μ-C₁₀H₈)FeCp*]. Cyclic voltammetry and UV-vis spectroelectrochemistry showed that 1 can be reversibly oxidized to 1⁺ and 1²⁺. Chemical oxidation with [Cp₂Fe]BAr^F₄ afforded the paramagnetic compound [1]BAr^F₄, which was investigated by EPR, single-crystal X-ray diffractometry and DFT calculations. Reaction of 1 with Brookhart's acid gave the hydride complex [3]BAr^F₄, which was characterized spectroscopically and crystallographically. Cyclic voltammetry showed that [3]⁺ is converted back to 1 upon reduction and oxidation.