Highly Oxidized Ruthenium Organometallic Compounds. The Synthesis and One-Electron Electrochemical Oxidation of [Cp*Ru^IVCl₂(S₂CR)] (Cp* = η⁵-C₅Me₅, R = NMe₂, NEt₂, OⁱPr)

[Cp*Ru^IVCl₂(S₂CR)] (R = NMe₂, NEt₂, and OⁱPr) were synthesized by the reaction of [Cp*Ru^IIICl₂]₂ with [RC(S)S]₂. One-electron electrochemical oxidation of [Cp*RuCl₂(S₂CR)] produces paramagnetic [Cp*RuCl₂(S₂CR)]⁺, which are stable in CH₂Cl₂ solution for at least several hours at 233 K. EPR experiments performed at 293 K show isotropic signals (g ≈ 2.035) with clearly defined hyperfine coupling to ⁹⁹Ru and ¹⁰¹Ru of 25 G and with peak-to-peak line widths of 15 G. At temperatures below 153 K, axial-shaped EPR spectra were obtained with g-values close to 2 (2.050−2.008) and narrow peak-to-peak line widths (15 G). Results from DFT calculations indicate that approximately 70% of the spin density in [Cp*RuCl₂(S₂CNMe₂)]⁺ is located on the ruthenium, although there is an increase of only 0.06 in the positive charge of the metal ion as a result of the oxidation. The high spin density on Ru supports the assignment of a formally Ru(V) oxidation state, which is unprecedented in organometallic chemistry. Chemical oxidation of Cp*Ru^IVCl₂(S₂CNMe₂) with NO(PF₆) in CH₃CN resulted in the isolation of [Cp*Ru^IV(MeCN)₂(S₂CNMe₂)]⁺² (4), while oxidation with [(4-Br-C₆H₄)₃N](SbCl₆) in CH₂Cl₂ resulted in the formation of chloro-bridged dimeric [Cp*Ru^IVCl(S₂CNMe₂)]₂⁺² (5). When 5 is dissolved in CD₃CN/CH₃CN, it immediately converts to 4. Cyclic voltammetric experiments confirmed that in both solvents the chemical oxidation process occurred through the [Cp*Ru^VCl₂(S₂CNMe₂)]⁺ intermediate.