Carbon dioxide clusters reactivity

The abundant chemistry of Ni(CO>4 under reductive reaction conditions leading to the formation of dinuclear nickel complexes or even to nickel clusters suggests the involvement of higher aggregates, however. An overview of the reactivity of nickel complexes, and of Ni(CO)4 in particular, is given in a series of excellent reviews by Jolly [13]. There seems to be evidence of an autocatalytic cycle for the formation of the active catalyst [14]. Parallel to this, the water-gas shift reaction (eq. (5)) occurs, resulting in the formation of carbon dioxide and hydrogen, which is known to form metal hydrides in the presence of metal carbonyls [15]. 

R = Me, Ph Ln = Y, Lu) with either H2 (Scheme 69)296 297 or PhSiHj,298 and their reactivity has been studied.297 299 300 This includes, for example, hydrogenation of carbon dioxide and aryl isocyanates.301 The effective group potentials (EGP) method has been used for predicting the properties of the trinuclear hydride clusters Gp II and Gpf,Lu3II4 -3°2... 

The morphology and properties of the carbon deposition of the nickel-based catalysts for carbon dioxide reforming of methane are investigated. Silica supported nickel catalysts were more facile to carbon deposition than alumina supported catalysts. The decomposition of methane resulted in the formation of at least three kinds of surface carbon species on supported nickel catalysts. Carbidic C , carbonaceous Cp and carbidic clusters Cy surface carbon species formed by decomposition of methane showed different thermal stability and reactivity. The carbidic carbon was a very active and important intermediate in the carbon dioxide reforming of methane and the carbidic clusters Cy species might be the precursor of the surface carbon deposition. The partially dehydrogenated Cp species can react with H2 or CO2 to form CH4 or CO. 

Fig. 25. Reactivity of platinum clusters supported on a MgO fllm as a function of the cluster-size. The reactivity is expressed in the number of carbon dioxide molecules produced either per Ptn cluster, panel (a), or per Pt atom, panel (b), in the cluster-catalyzed oxidation of carbon monoxide. (Adapted from Ref. 36.)...

---