Surface supported metal cluster carbonyls. Chemisorption, reactivity, and decomposition of Ru₃(CO)₁₂ on silica

Ru₃(CO)₁₂ supported on silica is oxidised by surface SiOH groups in presence of water and/or dioxygen to form oxidised species, probably incorporated into the silica surface, such as Ru^II(CO)_n(OSi{A figure is presented})₂ (n = 2, 3). The presence of air (involving both water and dioxygen) greatly accelerates this oxidative process. When supported in total absence of dioxygen, Ru₃(CO)₁₂ reacts with surface silanol groups to produce the grafted cluster HRu₃(CO)₁₀(OSi{A figure is presented}), which has been characterized by chemical methods and by infrared and Raman spectroscopies. The grafted cluster is not very stable; it is an intermediate in the formation, by controlled thermal decomposition, of both small metallic particles and some Ru^II(CO)_n(OSi{A figure is presented})₂ (n = 2, 3) carbonyl surface species (this oxidation by surface protons is also evidenced by the formation of molecular hydrogen). The formation of metallic ruthenium accounts for the production of hydrocarbons during the thermal decomposition.