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*Ir-N(IMeMe)Cl-2 and Cp*Ir-N(IMe)Cl-2 (Cp*(N) = eta(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 eta(5):eta(1)-Cp*(N)-IrCl2 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).