Arun Kumar

For the first time, palladium-rich nanospheres of Pd ₇ Se ₂ have shown to be electrocatalytically active towards HER. They require an overpotential of only 162 mV, and an extremely low Tafel slope value of 37 mV dec ⁻¹ is achieved.

Nanomaterials have been developed utilizing organosulphur compounds, and the applications of such nanomaterials have been explored in catalysis and electrocatalysis.

For the first time, palladium telluride nanoparticles have been explored for Oxygen evolution reaction (OER). Pd ₉ Te ₄ nanospheres have been synthesized by using a simple, hassle‐free, and one‐pot method, that is single source precursor route. Palladium(II) complex of a bidentate Schiff base having (Te,N) donor sites was thermolyzed at 220 °C under inert atmosphere to obtain Pd ₉ Te ₄ which showed excellent potential for OER. It needs an overpotential of only 310 mV to drive the anodic current density of 10 mAcm ⁻² and it has shown stability for more than 17 h.

During the last two decades, organosulfur compounds have been used in the field of transition metal catalysis. Some of such compounds are known for their ability to withstand their exposure to air and moisture. These compounds are very important ligands. They may be obtained using simple and smooth modular synthetic protocols which include nucleophilic substitution reactions. The development of click chemistry represents a new era of innovation. It is a lighthouse of reliable and efficient reactions. In recent past, click chemistry has also been applied for the synthesis of such organosulfur ligands specifically suited for the dynamic field of transition metal catalysis. In order to synthesize novel compounds containing sulfur and triazole ring, click chemistry is an advantageous methodology over other approaches. This article covers the general features and uses of this methodology for the development of catalytically active organosulfur compounds. The significant advances in the design of transition metal catalytic systems utilizing such ligands, their use in the catalysis of many chemical transformations are also covered in this article. Effort has also been made to present a comparative overview of the performances of such catalysts vis‐à‐vis the catalysts designed commonly used ligands. Catalytic performances have been discussed thoroughly in order to identify the impact of ligand architecture on efficacy of the catalyst. Effect of reaction conditions (such as time, temperature etc.) and mechanistic aspects have also been rationalized.

First heterogeneous catalytic system, having a covalently linked hybrid bidentate organotellurium ligand [i.e., PhTe–CH₂–CH₂–NH₂] on the surface of graphene oxide, has been synthesized with immobilized and stabilized Pd(0) nanoparticles. To the best of our knowledge, it is the first such catalytic system in which a heterogenized organotellurium ligand has been used. It has been well-characterized using different physicochemical characterization techniques viz. P-XRD, XPS, HR-TEM, EELS, FE-SEM, EDX, TGA, BET surface area analysis, FT-IR spectroscopy, and Raman spectroscopy. The Pd content of the final system has been quantified using ICP-OES. Its applications have been explored in Suzuki–Miyaura C–C cross coupling and C–O cross coupling reactions. Hot filtration experiments corroborate the heterogeneous nature of the catalysis. It is recyclable for up to five reaction cycles in Suzuki–Miyaura and C–O cross coupling with marginal loss in performance. It also catalyzes the reactions of chloroarenes such as chlorobenzene, 4-chloroaniline, 1-chloro-4-nitrobenzene, 4-chloroacetophenone, 4-chlorobenzophenone for Suzuki coupling, and 1-chloro-4-nitrobenzene, 4-chlorobenzonitrile, chlorobenzene, and 4-chlorotoluene for C–O coupling. P-XRD, FE-SEM, and EDX study reveals that the catalytic system retains its structural originality and functionality after recycling.

Nanomaterials have revolutionized various scientific and industrial domains due to their exceptional properties and diverse applications. Yet, challenges persist in achieving their controlled synthesis, stability, and recyclability, especially in catalysis. Organoselenium compounds are emerging as promising agents for the stabilization of nanomaterials, with high prospects for catalytic applications. This article covers the recent strides made in harnessing the potential of organoselenium compounds to stabilize diverse nanomaterials with applications in catalysis. Specifically, it delves into their effectiveness in Suzuki‐Miyaura cross‐coupling, C−O coupling, Sonogashira coupling, reduction of nitroarenes, synthesis of primary amides (in aqueous medium), and offers a comprehensive overview of this evolving field.

The application of an organotellurium ligand as a stabilizer of palladium nanoparticles has been reported, and these nanoparticles have the potential to catalyze the O -arylation of phenols, even with aryl chlorides having deactivating substituents.

Sonogashira coupling is a reaction of aryl/vinyl halides with terminal alkynes. It is used for the synthesis of conjugated enynes. Generally, copper (Cu) is required as a mediator for this reaction. It requires a long reaction time, high catalyst loading, or expensive ligands. Recently, homogeneous, heterogeneous, and nanocatalysts have been developed using organosulphur and organoselenium compounds as building blocks. Preformed complexes of metals with organosulphur and organoselenium ligands are used for homogeneous catalysis. Heterogeneous catalytic systems have also been developed using Cu, Pd, and Ni as metals. The nanocatalytic systems (synthesized using such ligands) include copper selenides and stabilized palladium(0) nanospecies. This article aims to cover the developments in the field of the processes and techniques used so far to generate catalytically relevant organic ligands having sulphur or selenium donor sites, the utility of such ligands in the syntheses of homogeneous, heterogeneous, and nanocatalytic systems, and critical analysis of their application in the catalysis of this coupling reaction. The results of catalysis are analyzed in terms of the effects of the S/Se donor, halogen atom of aryl halide, the effect of the presence/absence of electron-withdrawing or electron-donating groups or substituents on the aromatic ring of haloarenes/substituted phenylacetylenes, as well as the position (ortho or para) of the substitution. Substrate scope is discussed for all the kinds of catalysis. The supremacy of heterogeneous and nanocatalytic systems indicates promising future prospects.