Molecular catalysts immobilized on oxide supports are easy to design and are as selective and active as their homogeneous analogues. Furthermore, they take on the properties of heterogeneous catalysts because they can easily be separated from the reaction mixtures and recycled many times. Chelating phosphine linkers, which can be bound to oxide supports, such as silica via ethoxysilane groups, have been synthesized and characterized. These linkers readily bind to Pd and Cu complexes, which have been used in the Sonogashira cross-coupling reaction of aryl halides with terminal acetylenes. We used solid-state CP/MAS and high-resolution (HRMAS) NMR spectroscopy of slurries for characterizing all immobilized ligands and Pd and Cu complexes. Using these techniques helped us to gain insights into mechanistic aspects of the Sonogashira reaction. On this basis, we could obtain an immobilized Sonogashira Pd(0)/Cu(I)  catalyst system with unprecedented activity and lifetime.

Immobilized Sonogashira catalyst systems for C-C coupling reactions:  New mechanistic insights and improved recyclability

243rd National Meeting (2012)

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