Synthesis, structure, and reactivity of hydridobis(silylene)ruthenium(IV)- xantsil complexes (xantsil = (9,9-dimethylxanthene-4,5-diyl)bis(dimethylsilyl)) - A stabilized form of key intermediates in the catalytic oligomerization- deoligomerization of hydrosilanes

Ru {K²(Si,Si)-xantsil}(CO)(η⁶-C₆H ₅CH₃) (1) was found to be a catalyst for oligomerization-deoligomerization of HSiMe₂SiMe₃ to give H(SiMe₂)_nMe (n = 1-8 at 90°C for 2 days). Treatment of 1 with HSiMe₂SiMe₂OR (R = Me, f-Bu) led to quantitative formation of Ru{κ³(O,Si,Si)-xantsil}(CO)(H) {(SiMe₂⋯O(R)⋯SiMe₂)} (R = Me (2a), t-Bu (2b)), which also worked as a catalyst for oligomerization-deoligomerization of HSiMe₂SiMe₃. Based on these experimental results, a mechanism involving silyl(silylene) intermediates was proposed for the oligomerization-deoligomerization of HSiMe₂SiMe₃. Complex 2a reacted with MeOH in toluene-d₈ to give Ru{κ ²(Si,Si)-xantsil}(CO)(η⁶-toluene-d₈) and Me₂Si(OMe)₂ with evolution of H₂. Under a CO atmosphere, 2a was smoothly converted to its CO adduct Ru{κ ²(Si-Si)-xantsil}(CO)₂(H){(SiMe₂⋯O(Me) ⋯SiMe₂)} (3).