New iridium and rhodium chiral di-N-heterocyclic carbene (NHC) complexes and their application in enantioselective catalysis

New iridium and rhodium complexes prepared from C-2-symmetric trans-9,10-dihydro-9,10-ethanoanthracene-11,12-bis(1-R)-benzimidazolidine-2-ylidene ligands (R=Me, Pr-i, and diPh) have been synthesized and characterized. Their catalytic activities have been tested in enantioselective hydrogenation and hydroformylation reactions. The ee's for the reactions are low. Evidence indicates that even chelating di-N-heterocyclic carbene ligands are susceptible to reductive elimination.