Providing Support in Favor of the Existence of a PdII/PdIV Catalytic Cycle in a Heck‐Type Reaction |
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Authors: | Francisco Juliá‐Hernández Prof. Dr. Aurelia Arcas Prof. Dr. José Vicente |
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Affiliation: | Grupo de Química Organometálica, Departamento de Química Inorgánica, Facultad de Química, Universidad de Murcia, Murcia, 30071 Spain, Fax: (+34)?868‐887785 |
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Abstract: | The complex [Pd(O,N,C‐L)(OAc)], in which L is a monoanionic pincer ligand derived from 2,6‐diacetylpyridine, reacts with 2‐iodobenzoic acid at room temperature to afford the very stable pair of PdIV complexes (OC‐6‐54)‐ and (OC‐6‐26)‐[Pd(O,N,C‐L)(O,C‐C6H4CO2‐2)I] (1.5:1 molar ratio, at ?55 °C). These complexes and the PdII species [Pd(O,N,C‐L)(OX)] and [Pd(O,N,C‐L′)(NCMe)]ClO4, (X=MeC(O) or ClO3, L′=another monoanionic pincer ligand derived from 2,6‐diacetylpyridine), are precatalysts for the arylation of CH2?CHR (R?CO2Me, CO2Et, Ph) using IC6H4CO2H‐2 and AgClO4. These catalytic reactions have been studied and a tentative mechanism is proposed. The presence of two PdIV complexes was detected by ESI(+)‐MS during the catalytic process. All the data obtained strongly support a PdII/PdIV catalytic cycle. |
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Keywords: | C?C coupling Heck reaction mass spectrometry reactive intermediates palladium |
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