Metal Complex Catalysts Research Articles

Tailored Metal-Based Catalysts: A New Platform for Targeted Anticancer Therapies.

Innovative strategies for targeted anticancer therapies have gained significant momentum, with metal complexes emerging as tunable catalysts for more effective and safer treatments. Rational design and engineering of metal complexes enable the development of tailored molecular structures optimized for precision oncology. The strategic incorporation of metal complex catalysts within combinatorial therapies amplifies their anticancer properties. This perspective highlights the advancements in synthetic strategies and rational design since 2019, showing how tailored metal catalysts are optimized by designing structures to release or in situ synthesize active drugs, leveraging the target-specific characteristics to develop more precise cancer therapies. This review explores metal-based catalysts, including those conjugated with biomolecules, nanostructures, and metal-organic frameworks (MOFs), highlighting their catalytic activity in biological environments and their in vitro/in vivo performance. To sum up, the potential of metal complexes as catalysts to reshape the landscape of anticancer therapies and foster novel avenues for therapeutic advancement is emphasized.

The Importance of Mesoporous Materials (Silica, Alumina, and Zeolite) as Solid Supports for Metal Complex Catalysts in Organic Transformations

The Importance of Mesoporous Materials (Silica, Alumina, and Zeolite) as Solid Supports for Metal Complex Catalysts in Organic Transformations

Dinuclear Cu(I) molecular electrocatalyst for CO2-to-C3 product conversion

Molecular metal complex catalysts are highly tunable in terms of their CO2 reduction performance by means of their flexible molecular design. However, metal complex catalysts have challenges in their structural stability and it has not been possible to synthesize high-value-added C3 products due to their inability to perform C–C coupling. Here we show a CO2 reduction reaction catalysed by a Br-bridged dinuclear Cu(I) complex that produces C3H7OH with high robustness during the reaction. The C–C coupling reaction mechanism was analysed by experimental operando surface-enhanced Raman scattering analysis, and theoretical quantum-chemical calculations proposed the formation of a C–C coupling intermediate species with substrate incorporation between the two Cu centres. Molecular design guidelines based on this discovery offer an approach to developing next-generation catalysts that generate multicarbon CO2 reduction products.

Reducing the environmental impact of aluminum production through the use of petroleum pitch

This study is aimed at developing a technology for obtaining petroleum pitch as a binder for anode mass used in the electrolytic production of aluminum from fuel oils of catalytic liquid-phase oxidative oil cracking. A review of published data on the existing methods for obtaining petroleum pitch and its properties is carried out in order to define research directions. A method for producing petroleum pitch by catalytic liquid-phase oxidative cracking of crude oil using heterogeneous metal complex catalysts is proposed. The process of petroleum pitch production is shown to undergo several stages, including homogenization of fuel oil and modifying additives; oxidative cracking of fuel oil during heating of homogenized fuel oil in a furnace; catalytic liquid-phase oxidative cracking of fuel oil with removal of distillates; rectification of light fractions; condensation of distillates; collection of light oil products; oxidation of bottom residues by air and steam; removal of oxidation distillates and petroleum pitch; and pitch pelletizing. According to the conducted comparison of the as-obtained petroleum pitch with the B-1 coal tar pitch produced by the Altai Koks JSC, the proposed material meets the technological requirements of the Krasnoyarsk Aluminum Plant of the RUSAL company. In terms of sulfur content, the proposed petroleum pitch is superior to coal tar pitch. The experiments conducted at an aluminum plant showed the petroleum pitch to contain no harmful polyaromatic hydrocarbons, in particular, carcinogenic benz(a)pyrene. Therefore, replacement of coal tar pitch with petroleum pitch could provide technological and environmental advantages for primary aluminum producers, as well as for enterprises producing various carbon materials.

Mononuclear metal complex catalysts on supports: foundations in organometallic and surface chemistry and insights into structure, reactivity, and catalysis.

Catalysts that consist of isolated metal atoms bonded to solid supports have drawn wide attention by researchers, with recent work emphasizing noble metals on metal oxide and zeolite supports. Progress has been facilitated by methods for atomic-scale imaging the metals and spectroscopic characterization of the supported structures and the nature of metal-support bonding, even with catalysts in the working state. Because of the intrinsic heterogeneity of support surface sites for bonding of metals and the tendency of noble metal cations on supports to be reduced and aggregated, it is challenging to determine structures of individual metal complexes among the mixtures that may be present and to determine structures of catalytically active species and reactive intermediates. A central premise of this perspective is that synthesis of supported metal complexes that have nearly uniform structures-on supports such as dealuminated HY zeolite, chosen to have relatively uniform surfaces-is a key to fundamental understanding, facilitating progress toward determining the roles of the ligands on the metals, which include the supports and reactive intermediates in catalysis. Characterization of relatively uniform and well-defined samples nonetheless requires multiple spectroscopic, microscopic, and theory-based techniques used in concert and still leaves open many questions about the nature of reactive intermediates and catalytic reaction mechanisms.

THERMOCATALYTIC DESTRUCTION OF HEAVY PETROLEUM FOODS IN THE PRESENCE OF A METAL COMPLEX CATALYST

The oil and gas refining industry in Russia and other countries is faced with the challenge of searching for new highly active catalytic systems and innovative methods for processing various types of petroleum feedstocks, including heavy petroleum feedstocks. One of the main tasks of this industry is to increase the depth of processing of petroleum raw materials to obtain more valuable petrochemical products.The purpose of the work is to study the dependence of the thermal destruction of heavy petroleum feedstock – heavy vacuum gas oil from the AVT-5 unit of PJSC «Bashneft-Novoil» in the presence of a new metal-complex catalytic system, where the active component is a chlorferrate complex (NaFeCl4) in an amount of 10 %, deposited on a carrier representing is a deeply decationized Ymmm zeolite of the acidic form (H-form), when varying process conditions, temperature in the range from 450 to 550 °C and volumetric feed rate of raw materials – 1,75–2,50 h-1. The physicochemical characteristics of the metal complex catalyst – 10 % NaFeCl4 / HYmmm zeolite were studied: characteristics of the porous structure, study of the phase composition, study of the morphology of the surfaces of catalytic systems.During experimental studies, it was established that the 10 % NaFeCl4/HYmmm zeolite catalytic system has a highly developed surface with a pore distribution of micro-, meso- and macropore sizes (total pore volume ~ 0,64 cm3/g); preserves the degree of crystallinity of the lattices relative to the original support Ymmm. It has been established that thermocatalytic destruction of heavy vacuum gas oil in the presence of a metal complex catalyst leads to its deep and selective conversion. The data obtained indicate that in the studied modes of the thermal destruction process, it is possible to achieve the formation of unsaturated olefinic hydrocarbons of the composition C2-C4 ~ 20 % wt., gasoline fraction ~ 45 % wt., total light ~ 68 % wt.

Lewis acids as co-catalysts in Pd-based catalyzed systems of the octene-1 hydroethoxycarbonylation reaction

Abstract In this work, in order to develop new, efficient, and environmentally friendly methods for the preparation of practically valuable esters of carboxylic acids, the hydroalkoxycarbonylation reaction of octene-1 with various alcohols in the presence of metal–complex catalysts based on palladium phosphine complexes has been studied. Three-component systems based on PdCl2(PPh3)2 containing different ligands as stabilizers and Lewis acids as promoters were studied as catalysts. It is shown that the three-component system PdCl2(PPh3)2–PPh3–AlCl3 has the highest catalytic activity in the reactions studied. It was found that the reaction of hydroalkoxycarbonylation of octene-1 proceeds with the formation of a mixture of linear (ethyl ester of pelargonic acid) and branched (ethyl ester of 2-methylcaprylic acid) products. The influence of the ratio of initial reagents (different olefins and alcohols) and components of catalytic systems (different Pd complexes, ligands, and promoters) on the course of the process has been investigated, in which the conversion of octene-1 reached 88.5%. The optimal parameters of the reactions studied were determined.

Micellar catalysis: Polymer bound palladium catalyst for carbon-carbon coupling reactions in water.

Metallosurfactants, defined here as hydrophobic metal-containing groups embedded in hydrophilic units when dispersed in water, emanate in the formation of metallomicelles. This approach continues to attract great interest for its ability to serve as micellar catalysts for various metal-mediated chemical transformations in water. Indeed, relevant to green chemistry, micellar catalysis plays a preeminent function as a replacement for organic solvents in a variety of chemical reactions. There are several methods for the interaction of metal complexes (catalysts or catalyst precursors) and surfactants for producing micellar aggregates. A very effective manner for achieving this involves the direct bonding of the metal center to the amphiphilic polymeric materials. Herein, we describe the synthesis of a metallosurfactant containing a palladium complex covalently incorporated into a CO2-based triblock polycarbonate derived using a dicarboxylic acid chain-transfer agent. This amphiphilic polycarbonate was shown to self-assemble in water to provide uniform and spherical micelles, where the catalytic metal center is located in the hydrophobic portion of the micelle. The resulting metallosurfactant was demonstrated to effectively catalyze carbon-carbon coupling reactions at very low catalyst loadings.

Molecular Engineering of a Metal‐Organic Polymer for Enhanced Electrochemical Nitrate‐to‐Ammonia Conversion and Zinc Nitrate Batteries

AbstractMetal–organic framework‐based materials are promising single‐site catalysts for electrocatalytic nitrate (NO3−) reduction to value‐added ammonia (NH3) on account of well‐defined structures and functional tunability but still lack a molecular‐level understanding for designing the high‐efficient catalysts. Here, we proposed a molecular engineering strategy to enhance electrochemical NO3−‐to‐NH3 conversion by introducing the carbonyl groups into 1,2,4,5‐tetraaminobenzene (BTA) based metal‐organic polymer to precisely modulate the electronic state of metal centers. Due to the electron‐withdrawing properties of the carbonyl group, metal centers can be converted to an electron‐deficient state, fascinating the NO3− adsorption and promoting continuous hydrogenation reactions to produce NH3. Compared to CuBTA with a low NO3−‐to‐NH3 conversion efficiency of 85.1 %, quinone group functionalization endows the resulting copper tetraminobenzoquinone (CuTABQ) distinguished performance with a much higher NH3 FE of 97.7 %. This molecular engineering strategy is also universal, as verified by the improved NO3−‐to‐NH3 conversion performance on different metal centers, including Co and Ni. Furthermore, the assembled rechargeable Zn−NO3− battery based on CuTABQ cathode can deliver a high power density of 12.3 mW cm−2. This work provides advanced insights into the rational design of metal complex catalysts through the molecular‐level regulation for NO3− electroreduction to value‐added NH3.

Molecular Engineering of a Metal-Organic Polymer for Enhanced Electrochemical Nitrate-to-Ammonia Conversion and Zinc Nitrate Batteries.

Metal-organic framework-based materials are promising single-site catalysts for electrocatalytic nitrate (NO3 - ) reduction to value-added ammonia (NH3 ) on account of well-defined structures and functional tunability but still lack a molecular-level understanding for designing the high-efficient catalysts. Here, we proposed a molecular engineering strategy to enhance electrochemical NO3 - -to-NH3 conversion by introducing the carbonyl groups into 1,2,4,5-tetraaminobenzene (BTA) based metal-organic polymer to precisely modulate the electronic state of metal centers. Due to the electron-withdrawing properties of the carbonyl group, metal centers can be converted to an electron-deficient state, fascinating the NO3 - adsorption and promoting continuous hydrogenation reactions to produce NH3 . Compared to CuBTA with a low NO3 - -to-NH3 conversion efficiency of 85.1 %, quinone group functionalization endows the resulting copper tetraminobenzoquinone (CuTABQ) distinguished performance with a much higher NH3 FE of 97.7 %. This molecular engineering strategy is also universal, as verified by the improved NO3 - -to-NH3 conversion performance on different metal centers, including Co and Ni. Furthermore, the assembled rechargeable Zn-NO3 - battery based on CuTABQ cathode can deliver a high power density of 12.3 mW cm-2 . This work provides advanced insights into the rational design of metal complex catalysts through the molecular-level regulation for NO3 - electroreduction to value-added NH3 .

A Single Biaryl Monophosphine Ligand Motif—The Multiverse of Coordination Modes

Biaryl monophosphines are important precursors to active catalysts of palladium-mediated cross-coupling reactions. The efficiency of the phosphine-based transition metal complex catalyst has its origin in the electronic structure of the complex used and the sterical hindrance created by the ligand at an active catalyst site. The aim of this paper is to shed some light on the multiverse of coordination modes of biaryl monophosphine ligands. Here, we present the analysis of the X-ray single crystal structures of palladium(II) complexes of a family of biaryl monophosphine ligands and the first crystallographic report on a related phosphine sulfide. Despite the common biaryl monophosphine ligand motif, they show diverse coordination modes (i) starting from the activation of aromatic C atoms and producing a C,P metallacycle, through (ii) the O,P chelation to Pd(II) ions with a simultaneous demethylation reaction of one of the methoxy groups, ending up with (iii) the monodentate coordination to metal cations via P atoms or (iv) via S atoms in the case of phosphine sulfide. We relate our results to the crystal structures found in the Cambridge Structural Database to show the multiverse of coordination modes in the group of biaryl monophosphine ligands.

CO2 Activation with Manganese Tricarbonyl Complexes by an H-Atom Responsive Benzimidazole Ligand.

Herein, we report the synthesis and characterization of two manganese tricarbonyl complexes, MnI (HL)(CO)3 Br (1 a-Br) and MnI (MeL)(CO)3 Br (1 b-Br) (where HL=2-(2'-pyridyl)benzimidazole; MeL=1-methyl-2-(2'-pyridy)benzimidazole) and assayed their electrocatalytic properties for CO2 reduction. A redox-active pyridine benzimidazole ancillary ligand in complex 1 a-Br displayed unique hydrogen atom transfer ability to facilitate electrocatalytic CO2 conversion at a markedly lower reduction potential than that observed for 1 b-Br. Notably, a one-electron reduction of 1 a-Br yields a structurally characterized H-bonded binuclear Mn(I) adduct (2 a') rather than the typically observed Mn(0)-Mn(0) dimer, suggesting a novel method for CO2 activation. Combining advanced electrochemical, spectroscopic, and single crystal X-ray diffraction techniques, we demonstrate the use of an H-atom responsive ligand may reveal an alternative, low-energy pathway for CO2 activation by an earth-abundant metal complex catalyst.

Recent advancement in CO2 capturing: An electrochemical approach

Various methods have been suggested to address the problem of elevated levels of carbon dioxide (CO2) in the atmosphere. A potential technique among these strategies is the electrochemical reduction of CO2 (ERC), which can simultaneously solve issues like CO2-induced global warming and enable sustainable energy storage. The ERC procedure takes place within an electrochemical cell at the interface between an ionic conductor (the electrolyte) and an electron conductor (the cathode). In this process, the anode facilitates the oxidation of water, while the cathode enables CO2 reduction. However, a significant challenge in the ERC process lies in selecting an appropriate catalyst for the cathode material. In addition to explore the new transition metals, researchers have also investigated metal complex catalysts and nanostructures to enhance catalyst activity and product selectivity. Non-aqueous electrolytes have been employed to avoid the hydrogen evolution reaction. Ionic liquids have been proposed as a solution to address the challenge of low CO2 solubility in the reaction medium, offering significant potential for enhancing conversion rates to resolve the limitations faced by aqueous and non-aqueous systems solid polymer electrolytes are being considered. The cell configuration has been continuously improved to improve the mass transfer effects and to better separate the reaction products. This review paper provides a preface to the ERC process and an inclusive review of several decades of research work on ERC process by analyzing the adopted various and novel cathode materials, electrolytes and cell configuration.

Chiral Organocatalysts in Enantioselective CO2 Utilization Reactions

AbstractThe development of efficient CO2 utilization reactions has gained a significant amount of attention in recent years. Although transformations of CO2 to produce basic chemicals have been extensively investigated, the development of catalytic enantioselective CO2 utilization reactions for the preparation of fine chemicals remains limited at this stage. Several excellent methods for catalytic enantioselective CO2 utilization using chiral metal complex catalysts have been reported. Many researchers have also focused on developing organocatalyzed approaches to enantioselective CO2 utilization, and several excellent examples have appeared in recent years. Herein, recent advances in catalytic enantioselective CO2 utilization reactions using chiral organocatalysts are reviewed to provide a forecast for organocatalyzed enantioselective CO2 utilization research.

Iridium-Complexed Dipyridyl-Pyridazine Organosilica as a Catalyst for Water Oxidation.

The heterogenization of metal-complex catalysts to be applied in water oxidation reactions is a currently growing field of great scientific impact for the development of energy conversion devices simulating the natural photosynthesis process. The attachment of IrCp*Cl complexes to the dipyridyl-pyridazine N-chelating sites on the surface of SBA-15 promotes the formation of metal bipyridine-like complexes, which can act as catalytic sites in the oxidation of water to dioxygen, the key half-reaction of artificial photosynthetic systems. The efficiency of the heterogeneous catalyst, Ir@NdppzSBA, in cerium(IV)-driven water oxidation was thoroughly evaluated, achieving high catalytic activity even at a long reaction time. The reusability and stability were also examined after three reaction cycles, with a slight loss of activity. A comparison with an analogous homogeneous iridium catalyst revealed the enhanced durability and performance of the heterogeneous system based on the Ir@NdppzSBA catalyst due to the stability of the SBA-15 structure as well as the isolated metal active sites. Thereby, this new versatile synthesis route for the preparation of water oxidation catalysts opens a new avenue for the construction of alternative heterogeneous catalytic systems with high surface area, ease of functionalization, and facile separation to improve the efficiency in the water oxidation reaction.

Titania Nanoparticle Catalysed N‐Alkylation of Amines by Hydrogen Auto‐Transfer Mechanisms

AbstractUnlike well‐defined homogenous metal complex catalysts, no distinct heterogeneous catalysts are available for hydrogen auto‐transfer or borrowing hydrogen methodologies. Alternatively, a variety of noble metals, base metals, and bimetallic systems supported on various metal oxides are scrutinized for this purpose, mainly by modulating the ability of metals and supports in a multistep reaction. Herein, we demonstrate that pristine defect‐induced titania nanoparticle catalyst is an efficient and recyclable heterogeneous catalyst for the preparation of N‐alkylated products (>90 %) in the absence of expensive hydrogen source, costly ligands, additives, or costly metals under greener conditions. Furthermore, the nano‐sized titania catalyst tolerates functional groups with high yields. In addition, the ‐alkylation of aniline affords the corresponding alkylated products in d yields with long aliphatic alcohols. Finally, the results of the control tests show that a process of Hydrogen Auto transfer is responsible for carrying out the reaction.

Catalysts for Liquid-Phase Oxidation of Organic Compounds by Hydrogen Peroxide: Homogeneous and Phase-Transfer Systems

The review presents a comparative analysis of promising homogeneous metal complex catalysts and presents the results of studies on the synthesis and determination of the structural characteristics of effective catalysts for the oxidation of organic compounds with hydrogen peroxide – Q3{PO4[WO(O2)2]4} (Q is a quaternary ammonium cation) – using methods EXAFS, SAXS, NMR, Raman and IR spectroscopy. The possibilities of using bifunctional homogeneous peroxopolyoxo complexes of metals in combination with organic cations having quaternized nitrogen under the conditions of interfacial catalysis are considered, using examples of reactions of oxidation of various classes of organic compounds with hydrogen peroxide to obtain popular products – aliphatic and aromatic epoxides, mono- and dicarboxylic acids, as well as biologically active compounds for medical and agro-industrial purposes.

Heterobinuclear Metallocomplexes as Photocatalysts in Organic Synthesis

Photocatalytic processes under visible light have constantly been finding more and more applications in organic synthesis as they allow a wide range of transformations to proceed under mild conditions. The combination of photoredox catalysis with metal complex catalysis gives an opportunity to employ the advantages of these two methodologies. Covalent bonding of photocatalyst and metal complex catalyst using bridging ligands increases the efficiency of the electron and energy transfer between these two parts of the catalyst, leading to more efficient and selective catalytic systems. Up to now, after numerous investigations of the photocatalytic reduction of CO2 and hydrogen generation, such a strategy was firmly established to substantially increase the catalyst’s activity. This review is aimed at the achievements and perspectives in the field of design and application of heterobinuclear metal complexes as photocatalysts in organic synthesis.

Control of Selectivity in Homogeneous Catalysis through Noncovalent Interactions.

The regio-, site-, stereo- or chemoselective homogeneous catalytic transformations are extremely important for the growth/success of the current chemical industry. Based on empirical, theoretical or intuitive knowledge, several synthetic strategies, such as ligand design, transient directing group, metal node alternation, metal-ligand cooperation, pore decoration, biomimetic, have already been developed for the selective functionalization of organic substrates. In comparison to the other tactics, the use of noncovalent interactions for the control of selectivity in catalytic transformations of organic compounds may avoid multi-steps, reduce time of synthetic procedure, decrease cost of operation, and increase reactivity of catalyst. In fact, enzymes achieve a high selectivity through noncovalent interactions in biochemical processes in Nature. Guided by the impressive performance of enzymes in biosynthesis and biodegradation reactions, various types of synthetic metal complex or organocatalysts have already been developed, in which the catalyst-substrate noncovalent interactions have a pivotal impact on the distinctive stabilization of the transition states or intermediates, directing selectivity and improving efficiency of homogeneous catalytic reactions. Herein, we highlight several recent and relevant examples of selectivity directing/driving function of noncovalent interactions in the transformation of organic substrate(s) catalyzed by both organocatalysts and metal complex catalysts.

Unexpectedly easy non-catalytic transfer of allyl group from allyl sulfides to secondary phosphine sulfides

The unexpected allylation of secondary phosphine sulfides with allyl sulfides has been found. The reaction proceeds under mild conditions (no catalyst and solvent, 80°C) to give allyldiorganylphosphine sulfides (yield up to 79%). The latter, under the reaction conditions, are able to add the initial secondary phosphine sulfides across the allyl group in the anti-Markovnikov mode to deliver propane-1,3-diylbis(diorganylphosphine sulfides), promising extractants of heavy metals and ligands for the synthesis of metal complex catalysts.