An Ionic Liquid Immobilized Palladium Complex for an Effective Heck and Suzuki Coupling Reactions

Ionic Liquids in Metal, Photo-, Electro-, and (Bio) Catalysis

Ionic liquids (ILs) have unique physicochemical properties that make them advantageous for catalysis, such as low vapor pressure, non-flammability, high thermal and chemical stabilities, and the ability to enhance the activity and stability of (bio)catalysts. ILs can improve the efficiency, selectivity, and sustainability of bio(transformations) by acting as activators of enzymes, selectively dissolving substrates and products, and reducing toxicity. They can also be recycled and reused multiple times without losing their effectiveness. ILs based on imidazolium cation are preferred for structural organization aspects, with a semiorganized layer surrounding the catalyst. ILs act as a container, providing a confined space that allows modulation of electronic and geometric effects, miscibility of reactants and products, and residence time of species. ILs can stabilize ionic and radical species and control the catalytic activity of dynamic processes. Supported IL phase (SILP) derivatives and polymeric ILs (PILs) are good options for molecular engineering of greener catalytic processes. The major factors governing metal, photo-, electro-, and biocatalysts in ILs are discussed in detail based on the vast literature available over the past two and a half decades. Catalytic reactions, ranging from hydrogenation and cross-coupling to oxidations, promoted by homogeneous and heterogeneous catalysts in both single and multiphase conditions, are extensively reviewed and discussed considering the knowledge accumulated until now.

Ionic liquid immobilized Cu(I)–hydrazone–triphenylphosphine complex: an easily recyclable catalytic system for Suzuki and Heck cross couplings

A highly efficient, reusable, catalytic system of Heck and Suzuki cross-coupling reactions was observed for an inexpensive copper complex dispersed in ethyl-methyl imidazolium hexafluorophosphate medium, [EMIM]PF6. The reaction conditions were optimized by studying the effects of temperature, catalyst concentration, solvent, and time. This method functions for a variety of substrates towards the cross-coupling reactions. Most notably, the catalyst – ionic liquid mixture was easily recoverable and reused six times without much loss in the catalytic activity, causing a notably very low impact on the environment.