Polynuclear transition metal complexes hydride carbonyls

Asymmetric Synthesis by Homogeneous Catalysis Carbonyl Complexes of the Transition Metals Hydride Complexes of the Transition Metals Organic Synthesis using Transition Metal Complexes Containing tt-Bonded Ligands Polynuclear Organometallic Cluster Complexes. 

In a similar manner, NaBH4 reacts with almost all transition metal carbonyls to give anionic, polynuclear hydrides. Analogous reactions involving carbonyl complexes possessing other ligands are represented by the following ... 

Eliminations from Os(CO)4RR occur by dinuclear mechanisms only if either R or R is H. A hydride on one metal is necessary to interact with a vacant coordination site on the other in the dinuclear transition state. With Os(CO)4H2, the vacant site is created by dissociation of CO. With Os(CO)4-(H)CH the vacant site is created by a facile rate-determining isomerization which we suggest is to an acetyl hydride. The unique instability of hydridoalkyl carbonyls thus is explained. The synthesis and properties of Os(CO)4(H)C2H and various polynuclear ethyl osmium derivatives show that (3-hydrogens have no significant effect on these elimination mechanisms. Dinuclear hydridoalkyls are excellent starting points for the synthesis of more complex polynuclear alkyls. 

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