Formation of an Agostic Bond by Protonation. Characterization by NMR Spectroscopy of [(μ-H)₃M₃(μ₃-η²-HCR)(CO)₉][SO₃CF₃] (M = Ru, R = Et, CHPhCH₂Ph; M = Os, R = Me)

Protonation of (μ-H)₃M₃(μ₃-CX)(CO)₉(M = Ru, X = Et, CHPhCH₂Ph; M = Os, X = Me) in HSO₃CF₃solution yields [(μ-H)₃M₃(μ₃-η²-HCR) (CO)₉]⁺, in which the proton has been shown by¹H and¹³C NMR spectroscopy to add across a C–M edge. The agostic hydrogen is fluxionally exchanged among all three C–M bonds but does not exchange with the bridging hydrides. These protonated clusters prove to be more susceptible to reductive elimination of CH₃X than their neutral precursors. When M = Ru and X = H, Cl, Br, and Ph, addition of acid causes immediate cluster decomposition. When X = Ph and CHPhCH₂Ph, the reductive-elimination products toluene and 1,2-diphenylpropane have been identified.