Oxide-supported catalysts, from organometallic examples

In this chapter we report on the gas-phase preparation of metal-supported catalysts, that is on the deposition of dispersed metallic nanoparhcles onto a surface. Taking most of the examples from the thoroughly studied chemistry of the [Mo(CO)is]/oxide support system, we successively consider (i) surface organometallic chemistry issues, (ii) the methods used to avoid chemical contaminahon of the deposit and (iii) the competition between nucleation and growth. 

From an applied perspective, metals are probably the most important surfaces in SOMC. Whereas in SOMC on oxides we introduce the active site, in SOMC on metals the metals themselves are the active catalysts. Organometallic chemistry provides the means to modify the often unselective metal surface by introduction of organometallic complexes (most often chemically inert) to the surface and eventually by transforming the initially obtained species by thermal or chemical means. For example, the hydrogenolysis of cyclic hydrocarbons, in particular cyclohexane, on the surface of unmodified Ir particles supported on a silica carrier has been studied and clearly indicated to bimetallic mechanism of C-C bond cleavage (Scheme 4) [24, 25]. 

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