ABSTRACT Replacing conventional transition metals with main‐group elements for chemical bond activation and catalysis is of increasing interest, yet alkali metals remain largely underexplored in this context. Herein, we introduce a new strategy for alkali metal‐mediated catalysis based on metal–ligand cooperation (MLC) driven by dearomatization–aromatization of the ligand. Potassium pincer complexes bearing dearomatized picolyl ligands were synthesized and shown to activate a variety of molecules, including CO 2 , CS 2 , phenyl iso(thio)cyanates, ketones, and H 2 , thereby enabling the design of alkali metal catalysis. Notably, a dearomatized potassium complex efficiently catalyzed the hydrogenation of ketones and C─C multiple bonds, reactions that remain challenging in alkali metal catalysis. Density functional theory (DFT) calculations elucidated the electronic structures and bonding characteristics of the obtained complexes and provided mechanistic insight into the transformations. This work establishes a new paradigm in alkali metal chemistry and broadens the scope of MLC for bond activation and catalysis.

We report here an alternative approach to conducting the reverse water-gas shift (RWGS) reaction catalyzed by a ruthenium pincer complex and an amine. In this strategy, a secondary amine is first formylated by CO2 and H2 to make H2O and formamide. The formamide then undergoes decarbonylation to produce CO with the concomitant regeneration of the amine. Both steps, formylation and decarbonylation, were independently investigated through catalytic optimization studies and DFT computations at the PBE0-D3-(BJ)PCM(THF)/def2-TZVP level. Using morpholine and Ru-MACHO pincer catalyst, a TON of 249 was achieved for the hydrogenation of CO2 to CO (at 70 bar, 170 °C for 90 h) with 100% selectivity.

Here, we report a new class of pincer catalysts featuring a piperidine backbone that exhibits exceptional activity and longevity in the hydrogenation of esters, amides, and polyesters. The catalysts achieve turnover numbers of up to 1 million for ester hydrogenation, 50,000 for amide hydrogenation, and 490,000 for polyester hydrogenation, including the depolymerisation of post-consumer PET waste (up to 100,000), representing the highest values reported for these transformations. Mechanistic studies indicate that the rigid piperidine backbone enhances both catalyst stability and the concentration of catalytically active meridional dihydride species. These findings establish a platform for the development of highly efficient hydrogenation catalysts.

We have explored arylvinyl β-hydroxyacetonitrile as a 4π-electrocyclization precursor to access cyanomethyl indene in the presence of Lewis acids. Next, cyanomethyl indene was further reacted with an aromatic aldehyde to provide selective aryl/benzylation substitution on the indene ring. Furthermore, an electrocyclization reaction followed by selective benzylation of indene in one pot, as well as mechanistic studies to identify the source of hydrogen, was also conducted. Finally, we synthesized various substrates to demonstrate the substrate scope and limitation of this reaction, and the conversion of the nitrile group to its corresponding functional groups was also achieved, thereby expanding the scope of this approach.

The present study elucidates the impact of ancillary ligands on the electronic and photophysical properties of the complexes through effective design, synthesis and spectroscopic characterizations. Three different complexes with varying ancillary ligands i.e., acetylacetone (acac), dipivaloylmethane (dpm) and benzoylacetone (bza) and same cyclometalated ligand i.e.,2-(4-fluorophenyl) H-imidazo[1,2-a] pyridine (pip) are synthesized. Upon optical excitation, the molecules produce intense photoluminescence within the visible range with a moderate quantum yield. The variation in ancillary ligands tune the bandgap of the complexes resulting in a pronounced red shift in their emission characteristics. The electrochemical analysis suggests that the ancillary ligands shift the LUMO level of resulting complexes which accounts for the red shift in emission spectra. The DFT-TDDFT measurements further provide the supportive evidence of involvement of ancillary ligands in the frontier molecular orbitals (FMOs). To demonstrate the practical application of these complexes, different OLEDs with different device architectures have been fabricated. All the fabricated devices exhibit intense electroluminescence at room temperature with a maximum luminance of 1200 cd/m2 and peak external quantum efficiency of 13.9 % for device B. Lowest turn-on voltage of 3 volts has been achieved for device F.

ABSTRACT We report here two new approaches for the chemical recycling/upcycling of nitrile butadiene rubber (NBR) to make either polyamines or polyols. Both processes are achieved through ruthenium‐catalyzed hydrogenation reactions, where the chemoselective reduction of nitriles leads to the formation of either amines or alcohols. The hydrogenation of NBR to polyamines could be achieved at temperatures as low as 35°C, whereas a higher temperature (150°C) was required for the formation of polyols with catalytic turnover numbers reaching up to 2000. Additionally, polyamines were demonstrated for their potential application in CO 2 capture, absorbing 1.34 mmol of CO 2 /g of absorbents. This was significantly higher in comparison to that obtained in the case of NBR, which absorbed only 0.015 mmol of CO 2 /g of absorbent. The synthesized polyol exhibited a markedly greater ductility than the commercial NBR, reaching an elongation at break of ≈ 550% versus ≈ 420% for NBR, suggestive of potential use in stretch‐demanding applications.

For the synthesis of derivatives of 1, 2, 3-triazole, click chemistry has found remarkably extensive application which are key components in pharmaceuticals & therapeutic compounds. The methods that have been integrated are summarized in this review, which highlights a variety of robust and environmental-friendly protocols that use heterogeneous catalyts and nano-catalysts to produce 1,2,3-triazole derivatives. The review further explores the fusion of multicomponent reaction within click chemistry, which optimizes synthesis, reduces waste, and increases selectivity. The purpose of this investigation is to summarize methods of green synthesis and to highlight effective protocols that employ heterogeneous and nano-catalysts.

We report here the upcycling of PET (polyethylene terephthalate) waste via semihydrogenation to make ethyl 4‐(hydroxymethyl)benzoate. The reaction is catalyzed by a ruthenium pincer catalyst at 80 °C in bioderived solvents – a combination of 2‐methyl THF and ethanol. A detailed mechanistic investigation through organometallic and kinetic studies, as well as chemical exchange saturation transfer (CEST) NMR spectroscopy, provides insights into the nature of active species and factors that promote and inhibit the catalytic hydrogenation of PET. Using this mechanistic knowledge, a record high turnover number of >30 000 was achieved for the hydrogenative depolymerization of end‐of‐life PET waste (e.g., bottles and textiles). The semihydrogenation product, ethyl 4‐(hydroxymethyl)benzoate, was utilized to make precursors of various known pharmaceutical drugs, an agrochemical, as well as a new and recyclable polyester. A cradle‐to‐gate life cycle assessment demonstrated that using PET waste as a feedstock for EHMB production significantly reduces the environmental footprint compared to the conventional route from p ‐toluic acid.

This article gives a perspective on various types of catalytic dehydrogenative polymerization reactions (including organic and main group polymers) while introducing "hydrogen-borrowing polymerization" and "acceptorless dehydrogenative polymerization" to this class. Limitations and future opportunities of each method have been discussed.

Covalent organic frameworks (COFs) are crystalline porous materials bearing well-ordered two- or three-dimensional molecular tectons in their polymeric skeletal framework. COFs are structurally robust as well as physiochemically stable. Currently, these are being developed for their use as "heterogeneous catalysts" for various organic transformations. In particular, research on the use of COFs for catalysis for different C-C cross-coupling reactions is in its infancy. To date, COF catalysts reported for such reactions bear Pd(II) bound in an exclusive coordination environment and have been explored for a particular organic reaction. Herein, we report, for the first time, a COF (Pd@COF-TFP_TzPy) that can anchor Pd(II) units in the polymeric framework in two different coordination environments. Thus, Pd@COF-TFP_TzPy is a porous material with a dual confinement environment for Pd(II) units. The precursor COF (COF-TFP_TzPy) was easily synthesized and it features a two-dimensional hexagonal sheet structure for facile incorporation of Pd(II) ions. The loading of Pd(II) into Pd@COF-TFP_TzPy was low (4.85 wt% Pd), yet the material exhibited excellent catalytic activity in diverse C-C cross-coupling reactions with a broad substrate scope. Furthermore, Pd@COF-TFP_TzPy is highly stable and recyclable, thereby ensuring sustainable utilization of expensive Pd metal. We anticipate that our approach will stimulate further research into designing and utilizing functional COF materials for catalysis.

We report here a catalytic method to upgrade 1,4-benzenedimethanol to 3-(4-(hydroxymethyl)phenyl)propan-1-ol by coupling 1,4-benzenedimethanol with ethanol using a ruthenium catalyst. Through systematic optimization of catalytic conditions, a high TON of up to 400,000 has been achieved. Based on previous studies and those reported herein, we suggest that the reaction proceeds via a hydrogen-borrowing mechanism. Further upgradation of 1,4-benzendimethanol and 3-(4-(hydroxymethyl) phenyl) propan-1-ol through selective hydrodeoxygenation to make higher-value alcohols has also been demonstrated.

We report here a method for making polyesterether from ethylene glycol. The reaction is catalyzed by a ruthenium complex and liberates H2 gas and H2O as byproducts. Mechanistic studies conducted through experiments and DFT computations suggest that the chain growth of the polymerization process involves both dehydrogenation and dehydration pathways stemming from a hemiacetal intermediate, leading to the formation of esters and ethers, respectively. Investigations into the polymerization of other diols have also been conducted, showing that diols with a lower number of carbons between the alcohol groups (propylene glycol, glycerol, and 1,3-propanediol) lead to the formation of polyesterether whereas α,ω-diols containing a higher number of carbons (1,6-hexanediol and 1,10-decanediol) lead to the formation of polyester.

Herein, we report the stereoselective synthesis of 2,3-unsaturated α-O-aryl glycosides from disarmed glycals and challenging phenol as glycosyl acceptors using tris(pentafluorophenyl)borane (BCF) as an optimal catalyst. The optimized reaction conditions operate under metal-free conditions, affording the valuable 2,3-unsaturated-O-aryl glycosides in good to excellent yields with exclusive α-anomeric selectivity. The BCF catalyst not only activates the disarmed glycal donors but also enhances the nucleophilicity of electronically challenging phenol acceptors. A diverse range of glycosyl donors and acceptors were explored, and the method was further extended for scale-up synthesis and subsequent synthetic derivatization.

We report here the application of polyetherureas as a new class of aqueous binder for the LiFePO4 positive electrode material in lithium-ion batteries. Polyetherureas have been synthesized using a greener route (avoiding conventionally used toxic diisocyanate feedstock) by ruthenium-catalysed dehydrogenative coupling of polyethylene glycol diamine and methanol. The best binder performance was obtained when polyetherurea was used in combination with SBR (Styrene-Butadiene Rubber) exhibiting an initial coulombic efficiency of ~97% and a cell polarization of 30 mV. Remarkably, the combination of polyetherurea/SBR as a binder outperforms CMC (Carboxymethyl cellulose) which is a commonly used aqueous binder for lithium-ion batteries. Evidence of the involvement of polyetherureas on binder performance have been provided using IR spectroscopy, and scanning electron microscopy. Physical, electrochemical, and mechanical properties of the polyetherurea have been studied using TGA, DSC, powder XRD, cyclic voltammetry, nanoindentation, tensile testing and 180o peel test that shed light on why this polymer acts as a good binder.

We report here the upcycling of PET (polyethylene terephthalate) waste via semi-hydrogenation to make ethyl 4-(hydroxymethyl)benzoate. The reaction is catalysed by a ruthenium pincer catalyst at 80 °C in bio-derived solvents – a combination of 2-methyl THF and ethanol. A detailed mechanistic investigation through kinetic studies and chemical exchange saturation transfer (CEST) NMR spectroscopy provides insights into the nature of active species and factors that promote and inhibit the catalytic hydrogenation of PET. Using this mechanistic knowledge, a record high turnover number of > 30,000 was achieved. The semi-hydrogenation product, ethyl 4-(hydroxymethyl)benzoate, was utilised to make precursors of various known pharmaceutical drugs, an agrochemical, as well as a new and recyclable polyester.

We report here the hydrogenation of carbamates, ureas, and polyurethanes using heterogeneous catalysts. Under our catalytic conditions, carbamates and urea derivatives can be selectively hydrogenated to formamides and alcohols and amines, whereas polyurethanes were hydrogenatively depolymerized to make diamines and polyols. Recycling of catalysts for the hydrogenative depolymerization of a polyurethane has also been demonstrated 10 times.

We intended to realize aryl vinyl oxetane as a 4π-electrocyclization precursor to access indene ethanol. Interestingly, we found that the readily accessible aryl vinyl 1,3-diol, an intermediate en route to the synthesis of oxetane, is an equally potential precursor for the anticipated cyclization. Moreover, aryl vinyl 1,3-diol/oxetane and indene ethanol readily reacted with the subsequently added (het)aromatic aldehydes, providing various indene oxepines/acetaldehydes. Additionally, indenyl aldehyde served as a synthetic handle for FGI, further expanding this protocol's scope.

We report here a catalytic method to transform 1,4-benzenedimethanol to 3-(4-(hydroxymethyl)phenyl)propan-1-ol by coupling 1,4-benzenedimethanol with ethanol using a ruthenium catalyst. Through systematic optimization of catalytic conditions, a high TON of up to 400 000 has been achieved. Based on previous studies and those reported herein, we suggest that the reaction proceeds via a hydrogen-borrowing mechanism. Further conversion of 1,4-benzenedimethanol and 3-(4-(hydroxymethyl)phenyl)propan-1-ol through selective hydrodeoxygenation to make useful alcohols has also been demonstrated.