PEPPSI-Type Palladium Complexes Containing Basic 1,2,3-Triazolylidene Ligands and Their Role in Suzuki-Miyaura Catalysis

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Title: PEPPSI-Type Palladium Complexes Containing Basic 1,2,3-Triazolylidene Ligands and Their Role in Suzuki-Miyaura Catalysis
Authors: Canseco-Gonzalez, Daniel
Gniewek, Andrzej
Szulmanowcz, Michal
Müller-Bunz, Helge
Trzeciak, Anna M.
Albrecht, Martin
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Date: 7-May-2012
Online since: 2015-05-22T15:46:01Z
Abstract: A series of PEPPSI-type palladium(II) complexes was synthesized that contain 3-chloropyridine as an easily removable ligand and a triazolylidene as a strongly donating mesoionic spectator ligand. Catalytic tests in Suzuki–Miyaura cross-coupling reactions revealed the activity of these complexes towards aryl bromides and aryl chlorides at moderate temperatures (50 °C). However, the impact of steric shielding was the inverse of that observed with related normal Nheterocyclic carbenes (imidazol-2-ylidenes) and sterically congested mesityl substituents induced lower activity than small alkyl groups. Mechanistic investigations, including mercury poisoning experiments, TEM analyses, and ESI mass spectrometry, provide evidence for ligand dissociation and the formation of nanoparticles as a catalyst resting state. These heterogeneous particles provide a reservoir for soluble palladium atoms or clusters as operationally homogeneous catalysts for the arylation of aryl halides. Clearly, the substitution of a normal N-heterocyclic carbene for a more basic triazolylidene ligand in the precatalyst has a profound impact on the mode of action of the catalytic system.
Funding Details: European Research Council
Science Foundation Ireland
Type of material: Journal Article
Publisher: Wiley
Journal: Chemistry: A European Journal
Volume: 18
Issue: 19
Start page: 6055
End page: 6062
Copyright (published version): 2012 Wiley
Keywords: Cross-couplingHeterogeneous catalysisHomogeneous catalysisMesoionic carbenePalladium
DOI: 10.1002/chem.201103719
Language: en
Status of Item: Peer reviewed
Appears in Collections:Chemistry Research Collection

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