We have shown that reaction of Ru(PPh3)3(CO)H2 with the N-heterocyclic carbene (NHC) bis(1,3-(2,4,6-trimethylphenyl)imidazol-2-ylidene) (IMes) leads to both C-H and C-C bond activation of the aryl substituents on the carbene. The C-H activation chem. is reversible yielding a novel catalytic system that allows alcs. to be used as substrates for C-C bond formation. In a quest to find more active catalysts, we have turned to N-heterocyclic carbenes with alkyl substituents, including bis(1,3-ethyl-4,5-dimethylimidazol-2-ylidene) (IEt2Me2) and bis(1,3-cyclohexylimidazol-2-ylidene) (ICy). These allow formation of both mono- and bis-NHC complexes; in all of the mono cases, the NHC is trans to hydride, while in the bis carbene systems, the two carbenes lie cis to one another. The activity of these complexes in direct and transfer hydrogenation reactions of alkenes and ketones, as well as C-C bond forming reactions, will be described.
|Journal||Abstracts of Papers, 228th ACS National Meeting, Philadelphia, PA, United States, August 22-26, 2004|
|Publication status||Published - 2004|