Green pathways for palladium nanoparticle synthesis: Application and future perspectives

A simple green chemical method for the one step synthesis of palladium nanoparticles (PdNPs) and its application in organic synthesis has been described. Among the metallic NPs, Pd has a variety of applications in the field of homogeneous and heterogeneous catalysis, and therefore, greener pathways for its synthesis are focused. In particular, described herein is the recent development in synthesis of PdNPs through a greener setup in which phytochemicals present in plant extract will acts as a heterogeneous support and thus the need of external ligand is avoided. The detailed analysis of utilization of various plant extract for PdNPs synthesis and its characterization and application is specifically elaborated. The PdNPs have been synthesized from extracts of various portions of the plants in which presence of terpenes, citric acid, flavonoids, phenols, ascorbic acid, alkaloids, and reductase acts as potential reducing agents and stabilizers in nanoparticles synthesis. More importantly, higher surface area and optimum porosity are important factors in PdNPs to exhibit good catalytic activity. Notably, in a regular approach, reduction of Pd(II) to Pd(0) requires the expensive ligands, while in case of PdNPs' catalyzed transformation, it is achieved by phytochemicals present in the plant extract. In the later stage of the chapter, utilization of synthesized PdNPs for various organic transformations (e.g., Suzuki, Kumada, Sonogashira Heck, Suzuki-Miyaura, Negishi, Stille, or Kumada) is mainly described. Impertinently, the strategy of catalyst recyclability by various techniques is emphasized.