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{kappa(2)(Si,Si)-xantsil}(CO)(eta(6)-C6H5CH3) (1) was found to be a catalyst for oligomerization-deoligomerization of HSiMe2SiMe3 to give H(SiMe2)(n)Me (n = 1-8 at 90degreesC for 2 days). Treatment of 1 with HSiMe2SiMe2OR (R = Me, t-Bu) led to quantitative formation of Ru{kappa(3)(O,Si,Si)-xantsil}(CO)(H){(SiMe(2)oooO(R)oooSiMe(2))} (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-d(8) to give Ru{kappa(2)(Si,Si)-xantsil}(CO)(eta(6)-toluene-d(8)) and Me2Si(OMe)(2) with evolution of H-2. Under a CO atmosphere, 2a was smoothly converted to its CO adduct Ru{kappa(2)(Si,Si)-xantsil}(CO)(2)(H){(SiMe(2)oooO(Me)oooSiMe(2))} (3).