Facile O–H Bond Activation in Alcohols by [Cp*RuCl(iPr2PSX)] (X = Pyridyl, Quinolyl): a Route to Ruthenium(IV) Hydrido(alkoxo) Derivatives

The complexes [Cp*RuCl­(iPr2PSX)] (X = pyridyl, quinolyl) react directly with alcohols ROH (R = Me, Et, iPr, nPr) and NaBPh4, affording the novel cationic hydrido­(alkoxo) derivatives [Cp*RuH­(OR)­(iPr2PSX)]­[BPh4]. These ruthenium­(IV) compounds result from the formal oxidative addition of the alcohol to the 16-electron fragment {[Cp*Ru­(iPr2PSX)]+}, generated in situ upon chloride dissociation. The hydrido­(alkoxo) complexes are reversibly deprotonated by a strong base such as KOBut, yielding the neutral alkoxides [Cp*Ru­(OR)­(iPr2PSX)], which are remarkably stable toward β elimination and do not generate the corresponding hydrides. The hydrido­(alkoxo) complexes undergo a slow electron-transfer process, releasing H2 and generating the dinuclear ruthenium­(III) complex [{Cp*Ru­(κ2-N,S-μ S-SC5H4N)}2]­[BPh4]2. In this species, the Ru–Ru separation is very short and consistent with what is expected for a RuRu triple bond.