Search Results (68)

Background: Carbohydrate-derived chiral ligands are promising tools in asymmetric catalysis due to their structural diversity, chirality, and availability. However, ligands based on galactose or sorbose have been scarcely explored in the enantioselective addition of dialkylzinc reagents to aldehydes. Methods: A series of chiral diols and β-amino alcohols was synthesized from methyl D-glucopyranoside, methyl D-galactopyranoside, and D-fructose. These ligands were tested in the titanium tetraisopropoxide-promoted enantioselective addition of diethylzinc to aromatic and aliphatic aldehydes. Results: Several ligands, particularly those with a D-fructopyranose backbone, exhibited excellent catalytic activity, with conversion rates up to 100% and enantioselectivities up to 96% ee. Notably, this study reports for the first time the use of β-amino alcohols derived from fructose and sorbose in this transformation. Conclusions: Carbohydrate-based ligands represent effective, inexpensive, and structurally versatile scaffolds for developing highly enantioselective catalysts, expanding the utility of sugars in asymmetric organometallic reactions. Full article

Carbon materials, including graphene, carbon nanotubes, and fullerenes, serve as effective supports for catalysts and play a pivotal role in heterogeneous asymmetric catalysis due to their unique properties and ability to create defined environments for catalytic reactions. Recent research has focused on developing novel carbon-based catalysts that combine the advantages of heterogeneous catalysis with enhanced stability and reusability. This review highlights the synthesis and catalytic applications of graphene, carbon nanotubes, and fullerenes as heterogeneous support materials in asymmetric organocatalytic and organometallic reactions, covering their mechanisms, efficiency, and potential for advancing sustainable chemical processes. Full article

Chiral ansa-η⁵-complexes of transition metals have shown remarkable efficacy in organometallic synthesis and catalysis. Additionally, enantiomerically pure ansa-complexes hold promise for the development of novel chiral materials and pharmaceuticals. The discovery and synthesis of a diverse range of group IVB and IIIB metal complexes represents a significant milestone in the advancement of stereoselective catalytic methods for constructing metal-C, C-C, C-H, and C-heteroatom bonds. The synthesis of enantiomerically pure metallocenes can be accomplished through several strategies: utilizing optically active precursors of η⁵-ligands, separation of diastereomers of complexes with enantiomerically pure agents, and synthesis via the stereocontrolled reactions of enantiomerically pure σ-complexes with prochiral anions of η⁵-ligands. This review focuses on the analysis of various nuances of the synthesis of enantiomerically pure ansa-η⁵-complexes of titanium and lanthanum families. Their applicability as effective catalysts in asymmetric carbomagnesiation, carbo- and cycloalumination, oligo- and polymerization, Diels–Alder cycloaddition, reactions of zirconaaziridines, cyclization, hydrosilylation, hydrogenation, hydroamination, and other processes are highlighted as well. Full article

Recent developments in the synthesis of substituted polyacetylenes have considerably benefitted from advancements in organometallic catalysis; however, most important developments rely on the advent of Rh-catalyzed living polymerizations. The latter not only allow the tailoring of well-defined degrees of polymerization with low and narrow polydispersity but also enable access to stereochemical well-defined cis-transoidal polymers with a helical structure. These novel polymers open new avenues for application in photonics and electronics. Rh-catalyzed living polymerizations are mild and concise metal-catalyzed polymer syntheses that not only allow for the decoration of sidechains with multiple functionalities, including chiral units, but also enable enantioselective induction of helical chirality, memory of chirality, well-defined copolymerization, and end-group functionalization at both termini. This review summarizes recent developments in metal-catalyzed syntheses of substituted polyacetylenes, with a special focus on Rh-catalyzed living polymerizations. Full article

Ferrocene and its oxidized counterpart, the ferrocenium cation, represent a fascinating class of organometallic compounds with broad utility across various fields, including organic synthesis, pharmaceuticals, and materials science. Over the years, ferrocene, ferrocenium cations, and their derivatives have also gained prominence for their versatility in catalytic processes. This review article offers an overview of the research of the last decade into ferrocene- and ferrocenium-based catalysis. Key developments are highlighted in catalytic oxidation, cross-coupling, polymerization reactions, and redox-switchable catalysis, as well as the application of ferrocenium cations as Lewis acid catalysts. Full article

Carbon–carbon bond formation represents a key reaction in organic synthesis, resulting in paramount importance for constructing the carbon backbone of organic molecules. However, traditional metal-based catalysis, despite its advantages, often struggles with issues related to efficiency, selectivity, and sustainability. On the other hand, while biocatalysis offers superior selectivity due to an extraordinary recognition process of the substrate, the scope of its applicable reactions remains somewhat limited. In this context, Artificial Metalloenzymes (ArMs) and Metallo Peptides (MPs) offer a promising and not fully explored solution, merging the two fields of transition metal catalysis and biotransformations, by inserting a catalytically active metal cofactor into a customizable protein scaffold or coordinating the metal ion directly to a short and tunable amino acid (Aa) sequence, respectively. As a result, these hybrid catalysts have gained attention as valuable tools for challenging catalytic transformations, providing systems with new-to-nature properties in organic synthesis. This review offers an overview of recent advances in the development of ArMs and MPs, focusing on their application in the asymmetric carbon–carbon bond-forming reactions, such as carbene insertion, Michael additions, Friedel–Crafts and cross-coupling reactions, and cyclopropanation, underscoring the versatility of these systems in synthesizing biologically relevant compounds. Full article

This review covers recent advancements in the use of zirconium phosphates and phosphonates (ZrPs) as catalysts or catalyst supports for a variety of reactions, including biomass conversion, acid–base catalysis, hydrogenation, oxidation, and C-C coupling reactions, from 2015 to the present. The discussion emphasizes the intrinsic catalytic properties of ZrPs, focusing on how surface acidity, hydrophobic/hydrophilic balance, textural properties, and particle morphology influence their catalytic performance across various reactions. Additionally, this review thoroughly examines the use of ZrPs as supports for catalytic species, ranging from organometallic complexes and metal ions to noble metals and metal oxide nanoparticles. In these applications, ZrPs not only enhance the dispersion and stabilization of active catalytic species but also facilitate their recovery and reuse due to their robust immobilization on the solid support. This dual functionality underscores the importance of ZrPs in promoting efficient, selective, and sustainable catalytic processes, making them essential to the advancement of green chemistry. Full article

The application of organometallic materials as anodes in fuel cell devices has experienced a notable increase in recent years. However, the use of POCOP pincer complexes remains scarcely explored despite their great relevance in catalysis. Thus, in this work, the electrocatalytic activity to methanol in alkaline media of three Ni(II)-based POCOP pincer complexes—[NiCl{C₆H₂-4-OH-2,6-(OPiPr₂)₂}] (a1), [NiCl{C₆H₂-4-OH-2,6-(OPtBu₂)₂}] (a2), and [NiCl{C₆H₂-4-OH-2,6-(OPPh₂)₂}] (a3)—will be discussed. The complexes were use as modifiers of carbon paste electrodes that were evaluated using cyclic voltammetry considering diverse factors, such as the absence and presence of MeOH, diverse proportions (% w/w) of the complex in the electrode, scan rate, and different MeOH concentrations. Results indicated the presence of a redox pair Ni(II)/Ni(III) with a quasi-reversible behavior in all complexes, the anodic peak currents of which were proportional to the increase in MeOH concentrations (0.05–0.3 mM), and their oxidation potentials varied in the function of the P-substituent in the Ni(II)-POCOPs backbone. Complex a1 exhibited the best current density (429.5 mA cm² at 0.5 mM) compared to its analogs a2 and a3. The current intensity of all electrodes displays good stability, which remains—with slight changes—up to 100 s. Moreover, a comparison of their catalytic rate constants suggested a great activity in complex a1 (0.52 × 10⁶ cm³ mol⁻¹ s⁻¹) compared to its analogues, implying a great activity in the electro-oxidation of MeOH. Hence, this work opens new opportunities for the electrochemical application of POCOPs complexes for future DMFCs development. Full article

Five-membered saturated metallacarbocycles represent a large family of organometallic compounds, which are frequently postulated as reactive intermediates in catalysis or as precursors for the synthesis of a wide range of functionally substituted compounds, however, their NMR spectral data are incomplete and not systematized. Metallacarbocycles for Main III Group metals, which are spectroscopically characterized, are described in this article. Among these, of particular interest are 1-ethyl-3-substituted alumolanes, 3-spiro-substituted polycyclic alumolanes and nonbornen annelated alumolanes, which are supposedly formed by alkene cycloalumination with AlEt₃ catalyzed by Cp₂ZrCl₂. Conformational analysis upon inversion of a five-membered ring for mono and polycyclic alumolanes is presented. Full article

Covalent organic framework (COF)-supported palladium catalysts have garnered enormous attention for cross-coupling reactions. However, the limited linkage types in COF hosts and their suboptimal catalytic performance have hindered their widespread implementation. Herein, we present the first study immobilizing palladium acetate onto a dioxin-linked COF (Pd/COF-318) through a facile solution impregnation approach. By virtue of its permanent porosity, accessible Pd sites arranged in periodic skeletons, and framework robustness, the resultant Pd/COF-318 exhibits exceptionally high activity and broad substrate scope for the Suzuki–Miyaura coupling reaction between aryl bromides and arylboronic acids at room temperature within an hour, rendering it among the most effective Pd/COF catalysts for Suzuki–Miyaura coupling reactions to date. Moreover, Pd/COF-318 demonstrates excellent recyclability, retaining high activity over five cycles without significant deactivation. The leaching test confirms the heterogeneity of the catalyst. This work uncovers the vast potential of dioxin-linked COFs as catalyst supports for highly active, selective, and durable organometallic catalysis. Full article

Ferrocenyl-based compounds have many applications in diverse scientific disciplines, including in polymer chemistry as redox dynamic polymers and dendrimers, in materials science as bioreceptors, and in pharmacology, biochemistry, electrochemistry, and nonlinear optics. Considering the horizon of ferrocene chemistry, we attempted to condense the neoteric advancements in the synthesis and applications of ferrocene derivatives reported in the literature from 2016 to date. This paper presents data on the progression of the synthesis of diverse classes of organic compounds having ferrocene scaffolds and recent developments in applications of ferrocene-based organometallic compounds, with a special focus on their biological, medicinal, bio-sensing, chemosensing, asymmetric catalysis, material, and industrial applications. Full article

Ferrocene has been the most used organometallic moiety introduced in organic and bioinorganic drugs to cure cancers and various other diseases. Following several pioneering studies, two real breakthroughs occurred in 1996 and 1997. In 1996, Jaouen et al. reported ferrocifens, ferrocene analogs of tamoxifen, the chemotherapeutic for hormone-dependent breast cancer. Several ferrocifens are now in preclinical evaluation. Independently, in 1997, ferroquine, an analog of the antimalarial drug chloroquine upon the introduction of a ferrocenyl substituent in the carbon chain, was reported by the Biot-Brocard group and found to be active against both chloroquine-sensitive and chloroquine-resistant strains of Plasmodium falciparum. Ferroquine, in combination with artefenomel, completed phase IIb clinical evaluation in 2019. More than 1000 studies have been published on ferrocenyl-containing pharmacophores against infectious diseases, including parasitic, bacterial, fungal, and viral infections, but the relationship between structure and biological activity has been scarcely demonstrated, unlike for ferrocifens and ferroquines. In a majority of ferrocene-containing drugs, however, the production of reactive oxygen species (ROS), in particular the OH. radical, produced by Fenton catalysis, plays a key role and is scrutinized in this mini-review, together with the supramolecular approach utilizing drug delivery nanosystems, such as micelles, metal–organic frameworks (MOFs), polymers, and dendrimers. Full article

Ferrocene is useful in modern organometallic chemistry due to its versatile applications in material sciences, catalysis, medicinal chemistry, and diagnostic applications. The ferrocene moiety can potentially serve many purposes in therapeutics and diagnostics. In the course of this study, (6-bromo-1-oxohexyl)ferrocene was combined with dimercaptomaleonitrile sodium salt to yield a novel maleonitrile derivative. Subsequently, this compound was subjected to an autocyclotetramerization reaction using the Linstead conditions in order to obtain an octaferrocenyl-substituted magnesium(II) sulfanyl porphyrazine. Following that, both compounds—the maleonitrile derivative and the porphyrazine derivative—were subjected to physicochemical characterization using UV-Vis, ES-TOF, MALDI-TOF, and one-dimensional and two-dimensional NMR spectroscopy. Moreover, the sulfanyl porphyrazine was subjected to various photophysical studies, including optical absorption and emission measurements, as well as the evaluation of its photochemical properties. Values of singlet oxygen generation quantum yields were obtained in different organic solvents. The electrochemical properties of the synthesized compounds were studied using cyclic voltammetry. According to the electrochemical results, the presence of electron-withdrawing oxohexyl groups attached to ferrocene afforded significantly more positive oxidation potentials of the ferrocene-based redox process up to 0.34 V vs. Fc⁺/Fc. Full article

Calcium borohydride (Ca(BH₄)₂) is a complex hydride that has been less investigated compared to its lighter counterpart, magnesium borohydride. While offering slightly lower hydrogen storage capacity (11.5 wt% theoretical maximum, 9.6 wt% under actual dehydrogenation conditions), there are many improvement avenues for maximizing the reversible hydrogen storage that have been explored recently, from DFT calculations and polymorph investigations to reactive hydride composites (RHCs) and catalytic and nanosizing effects. The stability of Ca(BH₄)₂, the possibility of regeneration from spent products, and the relatively mild dehydrogenation conditions make calcium borohydride an attractive compound for hydrogen storage purposes. The ionic conductivity enhancements brought about by the rich speciation of borohydride anions can extend the use of Ca(BH₄)₂ to battery applications, considering the abundance of Ca relative to alkali metal borohydrides typically used for this purpose. The current work aims to review the synthetic strategies, structural considerations of various polymorphs and adducts, and hydrogen storage capacity of composites based on calcium borohydrides and related complex hydrides (mixed anions, mixed cations, additives, catalysts, etc.). Additional applications related to batteries, organic and organometallic chemistry, and catalysis have been briefly described. Full article

In the present paper, we compare the activity, selectivity, and stability of a supported nickel catalyst in classical heating conditions and in magnetically activated catalysis by using iron wool as a heating agent. The catalyst, 5 wt% Ni supported on titania (Degussa P25), was prepared via an organometallic decomposition method and was thoroughly characterized by using elemental, microscopic, and diffraction techniques. In the event of magnetic induction heating, the % CO₂ conversion reached a maximum of ~85% compared to ~78% for thermal conditions at a slightly lower temperature (~335 °C) than the thermal heating (380 °C). More importantly, both processes were found to be stable for 45 h on stream. Moreover, the effects of magnetic induction and classical heating over the catalyst evolution were discussed. This study demonstrated the potential of magnetic heating-mediated methanation, which is currently under investigation for the development of pilot-scale reactors. Full article