Synthesis and characterization of asymmetric NHC complexes

New chiral and non-chiral rhodium(I) - NHC complexes were synthesized. The first attempt by deprotonation of an imidazolinium salt with KOtBu and reaction with [Rh(COD)Cl](2) leads to the corresponding rhodium(I) complex. Due to the basic conditions during the reaction a loss of chirality occurs. An alternative transmetallation reaction with a silver(I) - NHC complex yields the desired rhodium (I) - NHC complex under retention of chirality. Both Rh complexes were fully characterized by analytical methods. (C) 2007 Elsevier B.V. All rights reserved.