Synthesis and Reactivities of Cp*Ir Amide and Hydride Complexes Bearing C−N Chelate Ligands

A series of 16-electron Cp*Ir amide complexes with C−N chelating ligands, Cp*Ir[κ 2 ( N, C )-(NHCR 2 -2-C 6 H 4 )] ( 2a: R = C 6 H 5, 2b: R = CH 3 ), and the chiral version, Cp*Ir[κ 2 ( N, C )-( R )-{NHCH(CH 3 )-2-C 10 H 6 }] ( 2e ), were obtained in good to excellent yields from reactions of 18-electron iridium amine complexes, Cp*IrCl[κ 2 ( N, C )-(NH 2 CR 2 -2-C 6 H 4 )] ( 1a: R = C 6 H 5, 1b: R = CH 3 ) and Cp*IrCl[κ 2 ( N, C )-( R )-{NH 2 CH(CH 3 )-2-C 10 H 6 }] ( 1e ), with a base. The amido complexes 2 readily reacted with 2-propanol to convert into hydrido(amine) complexes 3 in almost quantitative yields. The chiral amido complex has proven to serve as an efficient catalyst for asymmetric transfer hydrogenation of acetophenone with 2-propanol, giving 1-phenylethanol with a moderate ee. The Brønsted basicity on the metal−NH moiety in the amido complexes was evaluated by deprotonation of acetic acid, dimethyl malonate, and acetone, leading to the corresponding acetato(amine) complex 4 and alkyl(amine) complexes 5 and 6, respectively, indicating that the amido−Ir complexes bearing the C−N chelate have more basic properties than those with N-sulfonylated diamine ligands.