(Indenyl)ruthenium complexes containing 1,1′-bis(diphenylphosphanyl)- ferrocene (dppf) and thiolato ligands: Synthesis, X-ray structure analysis, electrochemistry and magnetic studies

The reaction of [(Ind)Ru(dppf)Cl] (Ind = η⁵-C ₉H₇) (2) with RSNa {R = Me, Et, Ph, Ph ₂P(CH₂)₂) proceeds in MeOH to give [(Ind)Ru(dppf)(SR)] {R = Me (3), Et (4), Ph (5), Ph₂P(CH ₂)₂ (7)}, as well as [(Ind)Ru(dppf)H] (6), in all cases except for R = Ph. This R-dependence of the product mixture was rationalised on a RS^-/MeOH ↔ MeO^-/RSH equilibrium involving the interaction of thiolate (RS^-) with MeOH, and the relative nucleophilicities of RS^- versus MeO^-; 6 arose from β-H elimination from an OMe derivative. Cyclic voltammetric measurements on 2, 3, 4 and 5, as well as the Cp (η⁵-C₅H₅) and Cp* (η⁵-C₅Me₅) analogues of 2, indicated that the formal oxidation potentials for [LRu(dppf)Cl] complexes {L = Ind (2), Cp (2A) and Cp* (2B)} occurred in the order Cp* < Ind < Cp, correlating with the more electron-donating groups lowering the oxidation potentials. EPR experiments performed on the one-electron oxidised forms of 3 and 5 indicated paramagnetic compounds with g values close to 2, while the two-electron oxidised forms of 3 and 5 were diamagnetic. All the complexes were characterised spectroscopically, and 5 and 6 also crystallographically.