Aerobic Alcohol Oxidation with Cationic Palladium Complexes:  Insights into Catalyst Design and Decomposition

Aerobic alcohol oxidation catalyzed by the newly synthesized dimeric (neocuproine)Pd(μ-OAc) 2 (OTf) 2 ( 1; neocuproine = 2,9-dimethyl-1,10-phenanthroline) proceeds under exceptionally mild conditions (room temperature, ambient air) compared to those required for the previously reported monomeric diacetate analogue (neocuproine)Pd(OAc) 2 ( 2 ) and the monomeric ditriflate analogue (neocuproine)Pd(MeCN) 2 (OTf) 2 ( 3 ). An unprecedented initial turnover frequency (TOF i ) for such mild conditions (78 (Pd atom) -1 h -1 ) is observed with catalyst 1; however, competitive oxidation of a methyl group on the ligand to a carboxylate group results in catalyst inactivation. During the study of 1, we isolated for the first time (neocuproine)Pd(μ-OH) 2 (OTf) 2 ( 4 ), a possible intermediate in the catalytic cycle, and we report its crystal structure and catalytic activity herein.