(CAAC)Pd(py) Catalysts Disproportionate to Pd(CAAC)<sub>2</sub>
Nicola Marigo, Bernd Morgenstern, Andrea Biffis, Dominik Munz
Abstract
High Resolution Image Download MS PowerPoint Slide Palladium complexes with one N -heterocyclic carbene (NHC) and a pyridine ancillary ligand are powerful cross-coupling precatalysts. Herein, we report such complexes with a cyclic (alkyl)(amino)carbene (CAAC) ligand replacing the NHC. We find that the alleged reduced form, (CAAC)Pd(py), disproportionates to the (CAAC) 2 Pd 0 complex and palladium nanoparticles. This notwithstanding, they are potent catalysts in the Buchwald–Hartwig amination with aryl chlorides under mild conditions (60 °C). In the presence of dioxygen, these complexes catalyze the formation of diazenes from anilines. The catalytic activities of the NHC- and CAAC-supported palladium(0) and palladium(II) complexes are similar in the cross-coupling reaction, yet the CAAC complexes are superior for diazene formation.