Synthesis of the first non-carbonyl cisoid fulvalene complexes with an Ru–Ru bond bridged by thiolate ligands

Abstract

The addition of PPh₃ to a solution which was produced by the oxidation of [(η⁵-Cp)Ru(μ₂-η⁶:η⁶-C₁₀H₈)Ru(η⁵-Cp)]²⁺(BF₄⁻)₂ (1) with p-benzoquinone and BF₃·OEt₂ (abbreviated as p-Bq/BF₃) in CH₂Cl₂–CH₃CN and subsequent Zn-reduction gave the transoid Ru–Fv complex (Fv = fulvalene) formulated as [(CH₃CN)₂(PPh₃)Ru(μ₂-η⁵:η⁵-C₁₀H₈)Ru(PPh₃)(CH₃CN)₂]²⁺(BF₄⁻)₂ (2a) in high yield as stable yellow crystals. Treatment of 2a with excess aryl thiols (ArSH; Ar = C₆H₅, p-CH₃C₆H₄ and p-ClC₆H₄), their thiolates and aryl dithiols (1,2-benzenedithiol or 3,4-toluenedithiol) or their dithiolates at room temperature afforded the Ru–Fv complexes bridged by thiolate ligands formulated as [(PPh₃)Ru(μ₂-η⁵:η⁵-C₁₀H₈)(μ₂-SAr)₂Ru(PPh₃)]²⁺(BF₄⁻)₂ (3a–c), (ArS)Ru(μ₂-η⁵:η⁵-C₁₀H₈)(μ₂-SAr)₂Ru(SAr) (4a–c) and [(PPh₃)Ru(μ₂-η⁵:η⁵-C₁₀H₈)(μ₂-S₂C₆H₃R)Ru(PPh₃)]²⁺(BF₄⁻)₂ (5a; R = H, 5b; R = CH₃), in high yield, respectively. Treatment of 2a with excess tert-butylthiolate produced the complex [(PPh₃)Ru(μ₂-η⁵:η⁵-C₁₀H₈)(μ₂-S^tBu)₂Ru]²⁺(BF₄⁻)(S^tBu⁻) (6a). In contrast with complexes 2–5, a coordinatively unsaturated Ru atom was found in 6a, which is probably formed owing to the bulkiness of the ^tBuS⁻ ligand. X-Ray analysis of complexes 3–6 showed the presence of an Ru^III–Ru^III single bond.