Axially chiral bidentate N-heterocyclic carbene ligands derived from BINAM: rhodium and iridium complexes in asymmetric ketone hydrosilylation

New bis(N-heterocyclic carbene) and N-heterocyclic carbene-naphthoxy ligands are synthesized in two steps from (S)-1,1'-diamino-2,2'-binaphthyl. Rhodium and iridium complexes of the carbene-naphthoxy ligands were applied to the catalytic asymmetric hydrosilylation of acetophenone with diphenylsilane. Low enantioselectivities (12-13% ee) were observed for the rhodium-catalyzed reaction, but moderate enantioselectivities (50-60% ee) were seen for iridium.