Mononuclear and trinuclear osmium carbonyl catalysts supported on SiO2, Al2O3, TiO2, and ZnO

Nature and Estimation of Functional Groups on Solid Surfaces

“…The Os-Os vibrations have been observed in the Raman spectrum [787]. The same reaction with surface hydroxyl groups has been observed with Ti0 2 [690,691], Zr0 2 [690], ZnO [691], MgO [788]. The reports on the necessary reaction temperature differ somewhat: room temperature [690], 398 K [691, 786],423 K [692].…”

“…The cluster disintegrates on heating at approximately 475 K [692], and two mononuclear species are formed, the IR spectra of which are similar to those of [OS(CO)3X2h and [Os(COhX2]n (X = Cl, Br, I) [691,692,786,787].…”

“…The reaction of alumina with OS3(CO)12 has been described in several nearly simultaneous publications [690][691][692]786]. The structure of the surface complex has been elucidated unambigously as It is analogous to the structure obtained on silica, and it may be inferred that it is the more acidic hydroxyl group on the oxide surface which reacts with the cluster.…”

“…The structure of this surface complex follows from IR spectra and from analogy with the reaction products of OS3(CO)12 with alcohols, phenols, or triphenylsilanol [690--693] The same surface compound was obtained in the reaction of silica with the cyclohexadiene complex OS3(C 6 Hs)(CO)10 [690]. When the triosmium surface cluster is heated to 673 K in helium or hydrogen, carbon monoxide and methane are given off [691], or carbon monoxide and hydrogen according to other authors [693], and a new surface species develops which is stable at 673 K in helium. Its infrared spectrum is similar to that of Os(CO)2I2.…”

“…The only well-characterized carbonyl cluster attached by chemical bonds to the silica surface is produced in the reaction with triosmium dodecacarbonyl, OS3(CO)12' a complex of particularly high stability. The light yellow surface complex, HOs 3 (CO)10-O-SIL, is formed in the reaction of an OS3(CO)12 solution in hexane with silica at room temperature [690] (other authors claim that refluxing in n-octane [691] or heating to 423 K [692,693] is necessary). The structure of this surface complex follows from IR spectra and from analogy with the reaction products of OS3(CO)12 with alcohols, phenols, or triphenylsilanol [690--693] The same surface compound was obtained in the reaction of silica with the cyclohexadiene complex OS3(C 6 Hs)(CO)10 [690].…”