Synthesis, Spectroelectrochemical, and EPR Spectroscopic Studies of Mixed Bis(alkynyl)biferrocenes of the Type (LnMC≡C)(LnM′C≡C)bfc

The synthesis and properties of a series of complexes containing bis(ethynyl)biferrocene as a bridge between different redox-active group 8 metal fragments is described. These metal acetylide compounds of type (LnMC≡C)(LnM′C≡C)bfc (5a, LnM = Fe(Cp*)(η2-dppe), LnM′ = Ru(Cp)(Ph3P)2; 5b, LnM = Fe(Cp*)(η2-dppe), LnM′ = Os(Cp)(Ph3P)2; 5c, LnM = Ru(Cp)(Ph3P)2, LnM′ = Os(Cp)(Ph3P)2; bfc = biferrocene-1′,1‴-diyl, ((η5-C5H4)2Fe)2; dppe = 1,2-bis(diphenylphosphino)ethane, C2H4(PPh2)2; Cp = η5-C5H5, Cp* = η5-C5Me5) were prepared either by treatment of (HC≡C)(LnM′C≡C)bfc (LnM′ = Ru(Cp)(Ph3P)2 (4b), Os(Cp)(Ph3P)2 (4c)) with Fe(Cp*)(η2-dppe)Cl (2a) or by the reaction of 4c with Ru(Cp)(PPh3)2Cl (2b) in the presence of [H4N][PF6] and KOtBu, respectively. Compounds 5a–c show well-separated reversible one-electron redox events in their cyclic voltammograms using [nBu4N][PF6] as supporting electrolyte in dichloromethane solutions. Absorption and vibrational spectroscopic studies were achieved for mixed-valence 5a–c[PF6] and...