Synthesis of New Iridium N-Heterocyclic Carbene Complexes Bearing a Functionalized Cp* Ligand and Their High Catalytic Activities in the Oppenauer-Type Oxidation of Alcohol

The new iridium N-heterocyclic carbene complexes Cp* N Ir(IMeMe)Cl 2 and Cp* N Ir(IMe)Cl 2 (Cp* N = η 5 -1-[2-(dimethylamino)ethyl]-2,3,4,5-tetramethylcyclopentadienyl; IMeMe = 1,3,4,5-tetramethylimidazol-2-ylidene; IMe = 1,3-dimethylimidazol-2-ylidene) have been synthesized by reaction of η 5:η 1 -Cp* N IrCl 2 with silver(I) carbene complexes or a free carbene. The catalytic systems using new iridium carbene complexes as a catalyst precursor and AgOTf showed high catalytic activities in Oppenauer-type oxidation of alcohol and were applicable to oxidations of acid-sensitive alcohols that had been hard to oxidize by using [Cp*Ir(IMeMe)(MeCN) 2 ][OTf] 2 .