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.

The syntheses of new NHC rhodium complexes are described. The reaction of [Rh(COD)Cl]2 with the free carbene leads to a non-chiral complex, while via transmetallation the chirality of the ligand is preserved.Figure optionsDownload as PowerPoint slide