Metal nanoparticles: ligand free approach towards coupling reactions

: Catalysis is a multidisciplinary field involving areas of organometallic chemistry, material science and engineering. It finds use in the synthesis of various industrially applicable compounds, such as fuels and fine chemicals. The activity and selectivity are fundamental issues to be dealt with in catalysis, which are associated with the high surface area. Current research activities primarily deal with homogeneous and heterogeneous catalysis. Although homogeneous and heterogeneous catalysis have been well researched, they have certain drawbacks that need to be overthrown for their wider applications. Therefore, it is imperative to find a catalytic protocol that would lead to higher selectivity and exemplary product yield with quick and easy retrieval. Along with being an alternative to conventional bulk materials, nanomaterials have further established their caliber into various industrial and scientific applications. Nanocatalysis has emerged as an advanced substitute for conventional homogeneous and heterogeneous catalysis. The nanomaterials are accountable for intensifying the surface area of a catalyst, ultimately resulting in an increase in the catalyst reactants' contacts. Furthermore, it enacts as a robust component providing high surface area like a heterogeneous catalyst. Nanoparticles can be yielded out of a reaction medium due to their insoluble behaviour, and thus, as catalysts, they can be retracted easily from the product. Hence, it has been proven that nanocatalysts enact as both homogeneous and heterogeneous catalysts, functioning as a bridge between the conventional catalytic systems. Considering these merits, researchers have tried to intensively study the applications of nanocatalysts in numerous organic reactions. This review article focuses on the catalytic applications of metal nanoparticles (MNPs), such as Pd, Ag, Au, Cu, Pt, in ligand-free coupling reactions. Also, it covers the applications of bimetallic and multimetallic nanoparticles in ligand-free coupling reactions.