Ruthenium clusters reaction with carbon monoxide

Catalysis by Metal Ousters in Zeolites. There is an increasing interest in the use of metal clusters stabilized in zeolites. One objective of such work is to utilize the shape and size constraints inherent in these support materials to effect greater selectivities in typical metal-catalysed reactions. Much work has been concerned with carbon monoxide hydrogenation, and although the detailed nature of the supported metals so obtained is not well understood, there is clear evidence of chain limitation in the Fischer-Tropsch process with both RuY zeolites and with HY and NaY zeolites containing Fe3(CO)22- In the former case there is a drastic decline in chain-growth probability beyond C5- or C10-hydrocarbons depending upon the particle size of the ruthenium metal. 

A very interesting deoxygenation reaction, in which carbon monoxide serves as both, a deoxygenating agent as well as a carbonylating agent, was found recently by Bhaduri et al. The formation of phenyl isocyanate from nitrobenzene with carbon monoxide is catalyzed by trinuclear ruthenium clusters such as Ru3(CO),2 or [HRu3(CO) ] ... 

The formation of carbido-carbonyl cluster compounds with ruthenium and osmium appears to be common in pyrolysis reactions the basic reaction may be viewed as the transformation of the coordinated carbon monoxide to carbide and carbon dioxide. Small variations in... 

It is not clear why the ruthenium catalyst is not able to induce the heterocyclisation from the presumably intermediate nitrene complex (Scheme 6). The benzamides 32 could be formed via the insertion of an intermediate isocyanate in the aromatic C-H bond of the solvent. This reaction has some precedents, where benzanilides were obtained by reaction of PhNCO with benzene, or directly from nitrobenzene, carbon monoxide and benzene, catalysed by rhodium carbonyl clusters [56-58], However, the reluctance of Ru3(CO)i2 to catalyse the reduction of nitrobenzene to phenylisocyanate in solvents such as benzene [22, 23] does not support this hypothesis. 

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