PUB - Publikationen an der Universität Bielefeld

Different chiral mono-substituted N-heterocyclic carbene complexes of rhodium were prepared, starting from [Rh(COD)Cl](2) (COD = cyclooctadiene) by addition of free N-heterocyclic carbenes (NHC), or an in-situ deprotonation of the corresponding iminium salt. All new complexes were characterized by spectroscopy methods. In addition, the structures of chloro(eta(4)-1,5-cyclooctadiene)(1,3-di-[(1R,2R,3R,5S)-2,6,6- trimethylbicyclo[3.1.1]hept-3-yl] imidazolin-2-ylidene) rhodium(I) (5a), chloro(eta(4)-1,5-cyclooctadiene)(1,3-di-[(1R,2S,5R)-2-isopropyl-5-menth ylcyclohex-1-yl] imidazol-2-ylidene)rhodium(I) (5b) and chloro(eta(4)-1,5-cyclooctadiene)(1,3-di-[(2R,4S,5S)-2-methyl-4-phenyl-1 ,3-dioxacyclohex-5-yl]imidazolin-2- ylidene)rhodium(I) (5i) were analyzed by DFT-calculations. The enantioselective hydrosilylation of acetophenone, ethylpyruvate and n-propylpyruvate with diphenylsilane and hydrolysis was carried out with chiral C(2)-symmetrical mono-substituted N-heterocyclic carbene rhodium complexes giving for the first time an enantioselective excess of up to 74% ee in the case of the n-propylpyruvate. (C) 2011 Elsevier B.V. All rights reserved.