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A variety of organoselenium compounds (containing Se donor site) have been used as ligand scaffolds for developing transition metal catalytic systems during the last two decades. Such compounds are known for their air- and moisture-insensitivity. Ligand design is an important and crucial aspect of homogeneous catalysis. A particular class of ligands emerges when it is easy and facile to carry out the modular synthesis of compounds pertaining to it. Generally, nucleophilic substitution reactions are used to design catalytically relevant organoselenium ligands. In the recent past, click chemistry, which represents efficient and reliable reactions, has also been used to develop organoselenium ligands for applications in transition metal catalysis. This perspective article describes the general features and applications of click chemistry used for the synthesis of selenium-containing compounds and their advantages over other synthetic approaches used for Se substituted ligands. Besides, it also covers the developments about the use of such ligands in the preparation of transition metal catalytic systems. Focus has also been laid down on the application of such systems in the catalysis of various chemical transformations (e.g. Suzuki–Miyaura coupling reactions, Heck reaction, Sonogashira coupling, oxidation of alcohols and transfer hydrogenation). Catalytic performances of such systems and variation due to a structural difference in ligand architecture have been critically analyzed. [ABSTRACT FROM AUTHOR]

Herein, we report a promising graphene oxide (GO) anchored robust and thermally stable heterogeneous catalytic system containing the low cost and less toxic copper oxide as a catalytically active material for C–O coupling reactions. A hybrid ligand (i.e. PPh2–CH2–CH2–NH2) has been used for the first time for functionalization of the GO surface. This ligand grafted over GO sheets via covalent linkages acts as an efficient stabilizing and chelating agent for CuO nanoparticles through P and N donor sites to form the catalytic system (GO–PN–CuO). The powder X-ray diffraction (PXRD), infrared (IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), Brunauer–Emmett–Teller (BET) studies, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM) and Raman spectroscopy confirmed the step-wise formation of GO–PN–CuO. The catalytic potential of GO–PN–CuO has been explored for the C–O coupling reactions of phenols with several aryl bromides and chlorides under mild reaction conditions. The covalent linkage of the hybrid ligand with GO sheets and the strong binding abilities of P, N donor sites with CuO render high stability to GO–PN–CuO. As a result, the catalytic system offers the advantage of recyclability up to five reaction cycles without any considerable loss in activity. [ABSTRACT FROM AUTHOR]

Organochalcogen compounds have been used as the building blocks for the development of a variety of catalysts that have been studied comprehensively during the last two decades for several chemical transformations. Transfer hydrogenation (reduction of carbonyl compounds to alcohols) and oxidation of alcohols (conversion of alcohols to their respective ketones and aldehydes) are also among such chemical transformations. Some compilations are available in the literature on the development of catalysts, based on organochalcogen ligands, and their applications in Heck reaction, Suzuki reaction, and other related aspects. Some review articles have also been published on different aspects of oxidation of alcohols and transfer hydrogenation. However, no such article is available in the literature on the syntheses and use of organochalcogen ligated catalysts for these two reactions. In this perspective, a survey of developments pertaining to the synthetic aspects of such organochalcogen (S/Se/Te) based catalysts for the two reactions has been made. In addition to covering the syntheses of chalcogen ligands, their metal complexes and nanoparticles (NPs), emphasis has also been placed on the efficient conversion of different substrates during catalytic reactions, diversity in catalytic potential and mechanistic aspects of catalysis. It also includes the analysis of comparison (in terms of efficiency) between this unique class of catalysts and efficient catalysts without a chalcogen donor. The future scope of this area has also been highlighted. [ABSTRACT FROM AUTHOR]