title: Poly(benzyl ether) Dendrimers Functionalized at the Core with Palladium Bis(N-Heterocyclic Carbene) Complexes as Catalysts for the Heck Coupling Reaction.
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.
authors.affiliation: Departamento de Química Orgánica y Química Inorgánica, Universidad de Alcalá, Edificio de Farmacia, Campus Universitario , E28871 Alcalá de Henares, Madrid, Spain.
authors.forename: Alba M
authors.initials: AM
authors.lastname: Ortiz
authors.affiliation: Departamento de Química Orgánica y Química Inorgánica, Universidad de Alcalá, Edificio de Farmacia, Campus Universitario , E28871 Alcalá de Henares, Madrid, Spain.
authors.forename: Alberto
authors.initials: A
authors.lastname: Sánchez-Méndez
authors.affiliation: Departamento de Química Orgánica y Química Inorgánica, Universidad de Alcalá, Edificio de Farmacia, Campus Universitario , E28871 Alcalá de Henares, Madrid, Spain.
authors.forename: Ernesto
authors.initials: E
authors.lastname: de Jesús
authors.affiliation: Departamento de Química Orgánica y Química Inorgánica, Universidad de Alcalá, Edificio de Farmacia, Campus Universitario , E28871 Alcalá de Henares, Madrid, Spain.
authors.forename: Juan C
authors.initials: JC
authors.lastname: Flores
authors.affiliation: Departamento de Química Orgánica y Química Inorgánica, Universidad de Alcalá, Edificio de Farmacia, Campus Universitario , E28871 Alcalá de Henares, Madrid, Spain.
authors.forename: Pilar
authors.initials: P
authors.lastname: Gómez-Sal
authors.affiliation: Departamento de Química Analítica, Química Física e Ingeniería Química, Universidad de Alcalá , E28871 Alcalá de Henares, Madrid, Spain.
authors.forename: Francisco
authors.initials: F
authors.lastname: Mendicuti