名称:
Highly Oxidized Ruthenium Organometallic Compounds. The Synthesis and One-Electron Electrochemical Oxidation of [Cp*RuIVCl2(S2CR)] (Cp* = η5-C5Me5, R = NMe2, NEt2, OiPr)
摘要:
[Cp*(RuCl2)-Cl-IV(S2CR)] (R = NMe2, NEt2, and (OPr)-Pr-i) were synthesized by the reaction of [Cp*(RuCl2)-Cl-III](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 approximate to 2.035) with clearly defined hyperfine coupling to Ru-99 and Ru-101 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*(RuCl2)-Cl-IV(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)(3)N](SbCl6) in CH2Cl2 resulted in the formation of chloro-bridged dimeric [Cp*(RuCl)-Cl-IV(S2CNMe2)](2)(+2) (5). When 5 is dissolved in CD3-CN/ CH3CN, it immediately converts to 4. Cyclic voltammetric experiments confirmed that in both solvents the chemical oxidation process occurred through the [Cp*(RuCl2)-Cl-V(S2CNMe2)](+) intermediate.