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.
(CAAC)Pd(py) Catalysts Disproportionate to Pd(CAAC)2
Biffis, Andrea;
2023
Abstract
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.Pubblicazioni consigliate
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