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

Abstract

Ru{κ2(Si,Si)-xantsil}(CO)(η6-C6H5CH3) (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, t-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{κ2(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{κ2(Si,Si)-xantsil}(CO)2(H){(SiMe2•••O(Me)•••SiMe2)} (3).Key words: silylene complex, ruthenium, polysilane, dehydrogenative coupling, oligomerization.