Synthesis of Ir Catalysts Featuring Amide-functionalized NHC Ligands and Survey of their Activity on Formic Acid Dehydrogenation

2 a and 2 b , Ir(CI)(COD)(NHC)] (COD=1,5-cyclooctadiene), have been prepared via transmetallation from NHC?Ag complexes. Rh(CI)(COD)(NHC)] ( 4 ) was prepared analogously. Ir({κ-C,N-(NHC-acetamide?1H)}(COD)] ( 3 c ) has been synthesized via transmetallation from the deprotonated NHC?Ag complex. IrCp*({κ-C,N-(NHC-acetamide?1H)}] ( 5 ) (Cp*=pentamethylcyclopentadienyl), has been obtained analogously. Ir(CI)(CO)₂(NHC)] ( 6 ) and Ir({κ-C,N-(NHC-acetamide?1H)}(CO)₂] ( 7 ) have been prepared by carbonylation of 2 b and 3 c , respectively. The catalytic activity of these complexes has been evaluated in the dehydrogenation of formic acid, under solventless conditions, in the presence of water as a cosolvent, and in a 5 : 2 HCOOH/Et₃N mixture, with the best TOF values being obtained in the case of the latter. Stoichiometric experiments suggest COD hydrogenation as the preactivation step.