Surface-supported metal cluster carbonyls. Chemisorption, decomposition and reactivity of Os3(CO)12, H2Os3(CO)10 and Os6(CO)18 supported on silica and alumina and the investigation of the fischer-tropsch catalysis with these systems

Nature and Estimation of Functional Groups on Solid Surfaces

“…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 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].…”

“…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.…”

“…These surface species can also be prepared by direct interaction with the mononuclear carbonyl halides [692]. The halogen is replaced by surface oxygen atoms in all likelihood.…”