Experimental and theoretical approaches to the influence of the addition of pyrene to a series of Pd and Ni NHC-based complexes: Catalytic consequences
Por:
Valdés H., Poyatos M., Ujaque G., Peris E.
Publicada:
1 ene 2015
Resumen:
A series of Ni and Pd complexes with three different N-heterocyclic carbene (NHC)-based ligands (imidazolylidene, benzimidazolylidene and pyrene-imidazolylidene) has been prepared and fully characterized. The influence of the addition of pyrene to solutions containing these complexes is studied by means of NMR and UV/Vis spectroscopies and by cyclic voltammetry. The addition of pyrene to the pyrene-NHC-containing Pd and Ni complexes gives rise to the formation of adducts by p-p stacking interactions between pyrene and the pyrene group of the NHC ligand. This interaction causes a modification of the electronic properties of the metal, as demonstrated by cyclic voltammetric studies of the Ni-NHC complexes. Theoretical calculations support this type of p-interactions, and justify the higher interactions observed with the pyrene-NHC containing complexes. The catalytic activities of the complexes were tested in the Suzuki-Miyaura C-C coupling and in the a-arylation of ketones. The addition of pyrene as an external p-stacking additive does not affect the activities of the complexes in the Suzuki-Miyaura coupling, but this observation may be justified due to the fact that the process is heterogeneously catalyzed, as indicated by the mercury-drop test. The addition of pyrene to the catalytic a-arylation of ketones results in a decrease in the activity of the reactions catalyzed by the pyrene-imidazolylidene palladium complex, whereas the other two catalysts do not modify their activity in the presence of this p-stacking additive. © 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Filiaciones:
Valdés H.:
Dpto. de Quimíca Inorgánica y Orgánica, Universitat Jaume I, Avda. Sos Baynat, Castellón, 12071, Spain
Poyatos M.:
Dpto. de Quimíca Inorgánica y Orgánica, Universitat Jaume I, Avda. Sos Baynat, Castellón, 12071, Spain
Ujaque G.:
Departament de Química, Universitat Autònoma de Barcelona, Cerdanyola del Vallès, Catalonia, 08193, Spain
Peris E.:
Dpto. de Quimíca Inorgánica y Orgánica, Universitat Jaume I, Avda. Sos Baynat, Castellón, 12071, Spain
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