The synthesis and redox behaviors of binuclear ruthenocene derivatives bridged by an aromatic moiety

2-Ruthenocenyl-4,4,5,5-tetramethyl-1,3-dioxa-2-borolane was prepared by the boration and the subsequent reaction with dilithium pinacolate as the starting material of the Suzuki–Miyaura coupling reaction. The dioxaborolane was heated with 1,4-dibromobenzene, 1,2-diiodobenzene, 4,4′-dibromobiphenyl, 1,4-dibromonaphthalene, and 2,6-dibromonaphthalene in the presence of (dppf)PdCl2–aqueous NaOH in DME to give the corresponding bis(ruthenocenyl) derivatives in moderate yields. The reaction of the dioxaborolane with 2,2′-diiodobiphenyl and 1,8-diiodo-naphthalene in the presence of Pd(PPh3)4–Cs2(CO)3 in N,N-dimethylformamide (DMF) produced ruthenoceno[l]phenanthrene and ruthenocenyl[a]acenaphthylene in low yield, respectively. The result of the cyclic voltammetry suggests that there is weak electronic interaction between the two metal sites in the two-electron oxidized species of the binuclear ruthenocene derivatives with an aromatic bridge.