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Updated: Mar 26, 2026

Palladium N-Heterocyclic Carbene Complexes: Synthesis from Benzimidazolium Salts and Catalytic Activity in Carbon-carbon Bond-forming Reactions
Published on: July 30, 2017
Poly(benzyl ether) Dendrimers Functionalized at the Core with Palladium Bis(N-Heterocyclic Carbene) Complexes as
Alba M Ortiz1, Alberto Sánchez-Méndez1, Ernesto de Jesús1
1Departamento de Química Orgánica y Química Inorgánica, Universidad de Alcalá, Edificio de Farmacia, Campus Universitario , E28871 Alcalá de Henares, Madrid, Spain.
Abstract:
Bis(imidazolylidene)palladium complexes 9-12 containing a sterically hindered aryl group (mesityl or 2,6-diisopropylphenyl) and a poly(benzyl ether) dendron as N-substituents of the NHC ligand are accessible up to the third generation by transmetalation of the corresponding silver complexes. Complexes 9-12 are soluble, active, and very stable catalysts under Heck reaction conditions. The NHC ligand appears to be stably coordinated to the Pd during catalysis. The catalytic activity increases with generation number, although irregularly. The palladium site is not significantly congested in the reaction solvent by the increasing size of the dendritic substituents, as corroborated by X-ray diffraction, fluorescence and DOSY-NMR spectroscopy, and MD simulation studies. This is a consequence of the conformational semiflexibility of the poly(benzyl ether) dendrons and the benzylic link between these dendrons and the N-heterocyclic ligands.
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