Applications of pincer bis-carbenes and polymer-supported phosphines in catalysis.

摘要

Two topics are discussed: catalysis with tridentate pincer bis-carbene Pd complexes and the synthesis of phosphines and their metal complexes on polymer support. Ir hydrogenation catalysts were synthesized on soluble support, while progress towards a phosphine library was made on insoluble support.; Chapters 2 and 3 describe the syntheses and catalytic activities of the pincer carbene Pd complexes. Pincers and carbenes, both robust ligand types in their own right, are combined to give ligands that form thermally and air stable Pd complexes. The modular ligand design allows variants to easily be synthesized. The use of longer alkyl groups on the pincer bis-carbene ligand improves solubility and Heck reaction activity at high temperature. Heck catalysis, mechanistic issues, and catalyst reuse are described. A bidentate monocarbene ligand analog shows the same activity and reaction profile as the pincer biscarbene for a single catalytic cycle, but cannot be reused.; Syntheses of poly(ethylene glycol)-bound triphenylphosphine and pyridine are discussed in Chapter 4. These soluble, polymer-bound ligands are loaded with Ir and used as water/substrate two-phase hydrogenation catalysts. Micelles formed during catalysis inhibited the separation of the two phases, but improved ligand and catalyst syntheses were achieved.; Finally, in Chapter 5, we explore techniques for making phosphine ligands in parallel on insoluble, crosslinked support, followed by loading of these phosphines with Ir and Rh precursors. Challenges associated with characterizing the phosphine library and the resulting metal complexes, along with the utility of a dye-based assay, are discussed.