Redox-Associated η1 to η2 Conversion of Disulfide Ligands in Dinuclear Ruthenium Complexes

Disulfide-bridged dinuclear ruthenium complexes [{Ru(MeCN)(P(OMe)3)2}2(μ-X)(μ,η2-S2)][ZnX3(MeCN)] (X = Cl (2), Br (4)), [{Ru(MeCN)(P(OMe)3)2}2(μ-Cl)2(μ,η1-S2)](CF3SO3) (5), [{Ru(MeCN)(P(OMe)3)2}2(μ-Cl)(μ,η2-S2)](BF4) (6), and [{Ru(MeCN)2(P(OMe)3)2}2(μ-Cl)(μ,η1-S2)](CF3SO3)3 (7) were synthesized, and the crystal structures of 2 and 4 were determined. Crystal data:  2, triclinic, P1̄, a = 15.921(4) Å, b = 17.484(4) Å, c = 8.774(2) Å, α = 103.14(2)°, β = 102.30(2)°, γ = 109.68(2)°, V = 2124(1) Å3, Z = 2, R (Rw) = 0.055 (0.074); 4, triclinic, P1̄, a = 15.943(4) Å, b = 17.703(4) Å, c = 8.883(1) Å, α = 102.96(2)°, β = 102.02(2)°, γ = 109.10(2)°, V = 2198.4(9) Å3, Z = 2, R (Rw) = 0.048 (0.067). Complexes 2 and 4 were obtained by reduction of the disulfide-bridged ruthenium complexes [{RuX(P(OMe)3)2}2(μ-X)2(μ,η1-S2)] (X = Cl (1), Br (3)) with zinc, respectively. Complex 5 was synthesized by oxidation of 2 with AgCF3SO3. Through these redox steps, the coordination mode of the disulfide ligand was converted from μ,η1 in 1 and 3 to μ,η2 in 2 and 4 and further reverted to μ,η1 in 5. Electrochemical studies of 6 indicated that similar conversion of the coordination mode occurs also in electrochemical redox reactions.