Trinuclear Simple Carbonyls

Trinuclear Simple Carbonyls. Comparison of kinetic data for Group V ligand replacement and CO exchange at the trinuclear carbonyl Ru3(CO)i2 suggests equilibrium loss of one CO molecule as the common initial, and rate-determining, step for both reactions. There is no evidence for radical 

Further information on the detailed mechanism of reaction of Ru3(CO)i2 with diphenylacetylene, which results in both displacement of CO by the acetylene and breakdown of the trimeric structure, has been obtained by characterisation of intermediates. The mechanism is slightly different from that observed for the analogous reaction of Fe3(CO)i2. Kinetic isotope effects associated with protonation (H, D) of polynuclear carbonyls have been further described. 

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The various modes of bonding that have been observed for alkenes to the trinuclear osmium clusters are shown in Fig. 7 [see (88)]. The simple 77-bonded structure (a) is relatively unstable and readily converts to (c) the vinyl intermediate (b) is obtained by interaction of alkene with H2Os3(CO)10 and also readily converts to (c) on warming. Direct reaction of ethylene with Os3(CO)12 produces (c), which is considered to be formed via the sequence (a) — (b) — (c) and (d). Both isomers (c) and (d) are observed and involve metal-hydrogen and metal-carbon bond formation at the expense of carbon-hydrogen bonds. In the reaction of Os3(CO)12 with C2H4, the complex 112088(00)902112, (c), is formed in preference to (d). Acyclic internal olefins also react with the carbonyl, with isomerization, to yield a structure related to (c). Structure (c) is... 

The chemistry of ruthenium carbonyl clusters is littered with instances where the simple trinuclear cluster acts as a catalyst. The list is lengthened by a study showing direct carbonylation of a C-H bond in a benzene ring of 2-phenyloxazo-lines catalysed by Ru3(CO)i2. 

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