pH-Induced Linkage Isomerism of Pd(II) Complexes: A Pathway to Air- and Water-Stable Suzuki-Miyaura-Reaction Catalysts.

The Pd(II) complexes of the ambidentate pyridyldiketones 2,2-dimethyl-5-(3- or 4-pyridyl)pentane-3,5-dione are readily prepared in their linkage isomeric forms by the appropriate pH control during syntheses. The isolated diketonate- or pyridine-bound species can be interconverted with essentially 100% efficiency by treatment with an acid or base, respectively. Under the normal basic conditions for a Suzuki-Miyaura coupling, only the diketonate forms are present and act as very efficient catalysts for this reaction. The dynamic nature of the presented complexes allows the catalytic process to be quenched and reactivated at any stage without the risk of losing the catalyst's activity.