(CAAC)Pd(py) Catalysts Disproportionate to Pd(CAAC)2

Palladium complexes with one N-heterocycliccarbene(NHC) and a pyridine ancillary ligand are powerful cross-couplingprecatalysts. Herein, we report such complexes with a cyclic (alkyl)(amino)carbene(CAAC) ligand replacing the NHC. We find that the alleged reducedform, (CAAC)Pd(py), disproportionates to the (CAAC)(2)Pd-0 complex and palladium nanoparticles. This notwithstanding,they are potent catalysts in the Buchwald-Hartwig aminationwith aryl chlorides under mild conditions (60 & DEG;C). In the presenceof dioxygen, these complexes catalyze the formation of diazenes fromanilines. The catalytic activities of the NHC- and CAAC-supportedpalladium(0) and palladium(II) complexes are similar in the cross-couplingreaction, yet the CAAC complexes are superior for diazene formation.

Automated summary

Palladium complexes with a novel cyclic (alkyl)(amino)carbene (CAAC) ligand are efficient cross-coupling precatalysts for the Buchwald-Hartwig amination reaction with aryl chlorides. We found that the reduced form of the complexes disproportionates to form a complex and palladium nanoparticles, but still exhibit excellent catalytic activity. In the presence of dioxygen, the CAAC complexes catalyze the formation of diazenes from anilines.