Dicyclophane imidazolium carbene

Several mono-NHC complexes were obtained. For example, transmetallation from a silver-NHC complex afforded the preparation of an Rh-NHC complex, in which the NHC ligand was obtained from caffeine. Deprotonation of chiral ferrocenyl imidazolium salts allowed the preparation of chiral Rh(l)-NHC complexes that could also be P,C and S,C chelate. Dicyclophane imidazolium carbene ligands also provided an efficient way of obtaining chiral Rh-NHC catalysts. ... 

Ma, Y., Song, C., Ma, C., Sun, Z., Chai, Q., and Andrus, M.B. (2003) Asymmetric addition of aryl boron reagents to enones with rhodium dicyclophane imidazolium carbene catalysis. Angew. Chem. Int. Ed., 42, 5871 5874. 

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