Nickel Catalysts Research Articles

Platinum–Chromium–Nickel Catalysts of Bicyclohexyl Dehydrogenation, Supported on Oxidized Sibunit Carbon

Platinum–Chromium–Nickel Catalysts of Bicyclohexyl Dehydrogenation, Supported on Oxidized Sibunit Carbon

Radical‐Driven Imine Hydrogenation Promoted by the Cooperativity of Nickel and a Redox‐Active Ligand

AbstractIn the case of N‐alkylation reaction via borrowing hydrogen (BH) methods, imine hydrogenation is one of the critical steps. Mechanistically, the majority of imine hydrogenation, either by dihydrogen gas or by alcohol in case of BH methods, follow two‐electron chemistry, where a metal‐hydride intermediate plays a pivotal role. Herein we demonstrate a completely complementary protocol, where the hydrogenation is governed by a radical pathway. Such a pathway is adopted from the redox active nature of the azophenolate ligand backbone. The facile and reversible 2e−/2H+, azo/hydrazo redox couple in a nickel catalyst helps in storing the hydrogen from alcohol dehydrogenation. An imine substrate is reduced by one‐electron from the azo motif with the assistance of the nickel center. The reduced imine drives a critical hydrogen atom transfer step from the hydrazo motif to conduct the hydrogenation. A set of kinetics experiments including Eyring analysis, radical inhibition experiment along with computational probation attest for the radical‐promoted hydrogenation mechanism.

Ni‐Catalyzed [2+2+2] Cycloaddition of Alkynes To Form Arenes and Pyridines at Low Catalyst Loadings

AbstractWe report the Ni‐catalyzed cyclotrimerization of terminal alkynes at very low loadings of catalysts (0.05 mol% for all substrates). The nickel catalyst containing a terphenyl phosphine ligand allows carrying out the reactions at room temperature in only 30 min, providing the arene products as a single regioisomer in most cases. The Ni complex is also competent for the synthesis of polysubstituted pyridines through the cycloadditions of diynes and nitriles at mild temperatures (25 ° or 50 °C) and low Ni loadings (1 mol%). Experimental data and computational studies support the involvement of monoligated PNi species in all fundamental steps of the catalytic cycle.

Asymmetric Synthesis of Polycyclic Heterocyclic Compounds via Friedel-Crafts Reaction/Cyclization Reaction Catalyzed by Nickel Catalyst.

The first highly enantioselective asymmetric Friedel-Crafts reaction/cyclization reaction of 5-aminopyrazoles with 3-alkenyloxindoles to afford polycyclic heterocyclic compounds bearing an all-carbon quaternary stereocenter catalyzed by a complex of NiII with the C2-symmetric bipyridine-N,N'-dioxide ligand L12 has been developed. The relevant products with a wide range of substrates and good functional tolerance were obtained in 89-98% yield with 56-99% ee in the presence of 10 mol % Ni(OTf)2 and 11 mol % L12 in DCM at 25 °C. Moreover, an experiment on scaling up the process along with the transformations of the cycloadducts further emphasized the practical application of the synthesis.

Manganese- and Iron-Catalyzed Carbonylation Reactions: A Personal Account

AbstractTransition-metal-catalyzed carbonylative transformations have been widely employed to convert CO gas into valuable carbonyl-containing molecules, mainly using noble metals (Pd, Rh, Ir, Ru) and more recently nickel and other catalysts. Although noble-metal catalysts have the advantage of reaction efficiency, their high-cost has led scientists to explore alternative procedures. Also under these backgrounds, we carried out some studies on nonexpensive metal-catalyzed carbonylative transformations. In this Account, we summarize the carbonylation reactions developed in our research group by using manganese and iron catalysis. These carbonylation reactions proceeded either via SET (single-electron transfer) or TET (two-electron transfer) mechanism.1 Introduction2 Manganese-Catalyzed Carbonylation of Alkyl Chlorides3 Manganese-Catalyzed Carbonylation of Alkyl Iodides4 Iron/Copper-Catalyzed Carbonylation of Alkyl Bromides5 Iron-Catalyzed Carbonylation of Alkyl Bromides6 Iron-Catalyzed Carbonylation of Alkyl-Boronic Pinacol7 Iron-Catalyzed Aminoalkylative Carbonylative Cyclization of Alkenes8 Conclusion and Outlook

Molecular docking, ADME properties and synthesis of thiophene sulfonamide derivatives

This study investigates the drug-like properties of target molecules containing thiophene sulfonamide groups (7a–7s) using computational molecular docking techniques. The binding interactions of these derivatives were assessed using protein 2NSD (Enoyl acyl carrier protein reductase InhA, complexed with N-(4-methylbenzoyl)-4-benzylpiperidine, PDB DOI: 10.2210/pdb2NSD/pdb) as the receptor. Molecular docking results revealed notable docking scores for all compounds, ranging from −6 to −12 kcal/mol. Compounds 7e, 7i, and 7f, in particular, demonstrated impressive glide scores (>11 kcal/mol) and were selected for further analysis through molecular dynamics simulations, which provided deeper insights into their dynamic behavior and stability. The drug-like properties of these molecules were evaluated based on Lipinski’s Rule of Five and ADME (Absorption, Distribution, Metabolism, and Excretion) criteria and compared with known drugs. Additionally, we synthesized these target molecules (7a–7s) using Suzuki-Miyaura coupling with a nickel catalyst replacing palladium. The chemical structures of the synthesized compounds were confirmed through elemental analysis, LC-MS,1H-NMR, and 13C-NMR spectroscopy.

Integrated Carbon Dioxide Capture by Amines and Conversion to Methane on Single-Atom Nickel Catalysts.

Direct electrochemical reduction of carbon dioxide (CO2) capture species, i.e., carbamate and (bi)carbonate, can be promising for CO2 capture and conversion from point-source, where the energetically demanding stripping step is bypassed. Here, we describe a class of atomically dispersed nickel (Ni) catalysts electrodeposited on various electrode surfaces that are shown to directly convert captured CO2 to methane (CH4). A detailed study employing X-ray photoelectron spectroscopy (XPS) and electron microscopy (EM) indicate that highly dispersed Ni atoms are uniquely active for converting capture species to CH4, and the activity of single-atom Ni is confirmed using control experiments with a molecularly defined Ni phthalocyanine catalyst supported on carbon nanotubes. Comparing the kinetics of various capture solutions obtained from hydroxide, ammonia, primary, secondary, and tertiary amines provide evidence that carbamate, rather than (bi)carbonate and/or dissolved CO2, is primarily responsible for CH4 production. This conclusion is supported by 13C nuclear magnetic resonance (NMR) spectroscopy of capture solutions as well as control experiments comparing reaction selectivity with and without CO2 purging. These findings are understood with the help of density functional theory (DFT) calculations showing that single-atom nickel (Ni) dispersed on gold (Au) is active for the direct reduction of carbamate, producing CH4 as the primary product. This is the first example of direct electrochemical conversion of carbamate to CH4, and the mechanism of this process provides new insight on the potential for integrated capture and conversion of CO2 directly to hydrocarbons.

Effect of nickel catalyst thickness on growth of carbon nanotubes on glass nonwoven mat using thermal chemical vapor deposition method

This study aimed to explore how varying the thickness of nickel catalyst affects the synthesis of carbon nanotubes on glass mats using the thermal chemical vapor deposition (TCVD) method. Nickel served as the catalyst, with acetylene as the hydrocarbon source and argon as the carrier gas. Initially, different thicknesses of nickel catalyst were applied to the glass mat via plasma-enhanced chemical vapor deposition (PECVD). Subsequently, these samples underwent TCVD plasma treatment. Electrical resistance measurements were conducted, and scanning electron microscopy (SEM), Raman spectroscopy, and transmission electron microscopy (TEM) were employed to analyze the presence, surface morphology, and quality of the nanotubes. The research revealed that the thickness of the nickel catalyst significantly influences the nanotube synthesis process on glass mat substrates. An optimal thickness of nickel catalyst yielded a glass mat with an electrical resistance of 2 Ω per unit area post-TCVD treatment.

Disparity between rate and selectivity in the controlled synthesis of gradient conjugated copolymers

In this report, a one-pot synthesis of gradient copolymers is attempted employing Kumada catalyst transfer condensative polymerization (KCTCP). The hypothesis that a more reactive monomer is preferentially being built into the chain at the beginning, while the slower reacting monomer is only being built into the chain at the end due to it being in excess, is investigated. The monomer rate constants are influenced by the usage of differently sized sidechains (octyl versus 3-octyldodecyl) and nucleophilicity of the monomers (thiophene versus selenophene). Nonetheless, while the rate constants differ by a factor 2, no selectivity is obtained. The cause thereof is further investigated by increasing the sterical crowdedness around the catalyst-complex by employing a 4-substituted monomer, the polymerization of which also gave rise to random copolymers. Accompanied by density functional theory calculations of the geometry and Gibbs free energy, it is concluded that the distance between the nickel catalyst and the polymer chain is much smaller compared to the distance between the catalyst and the incoming monomer. This results in different polymerization rates (depending on the polymer-nickel complex), while having no selectivity for one incoming monomer over the other.

The effect of carbon supports on the electrocatalytic performance of Ni-N-C catalysts for CO2 reduction to CO

Carbon-supported nickel and nitrogen co-doped (Ni-N-C) catalysts have been extensively studied as selective and active catalysts for CO2 electroreduction to CO. Most studies have focused on adjusting the coordination structure of Ni-Nx active sites, while the impact of the carbon supports has often been overlooked. In this study, a series of Ni-N-C catalysts on different carbon supports, including carbon black (CB), multi-walled carbon nanotubes (CNT), and activated nitrogen-doped biochar (ANBC), were synthesized using a ligand-mediated method. The effect of the carbon support on the electrocatalytic performance for CO2 reduction was investigated at both low current densities, in a H-cell, and high current densities, in a MEA electrolyzer. All of the prepared Ni-N-C catalysts show good faradaic efficiencies (FE) toward CO production (up to ~90%), however, the onset potentials and partial current densities for CO production vary greatly. The textural properties of the carbon support and the distribution of Ni-Nx active sites on the carbon support are demonstrated as the main factors behind the performance differences. In particular, hierarchical porous structures with large specific surface area are helpful to facilitate mass transport and improve the dispersion of active sites, which allows for a better CO2 reduction performance of Ni-N-ANBC compared to Ni-N-CB and Ni-N-CNT. This study demonstrates the importance of the carbon support for Ni-N-C catalysts and provides new insights into the design of efficient Ni-N-C catalysts for the CO2RR.

SELECTIVE HYDROGENATION OF ISOPRENE, PIPERYLENE AND THEIR MIXTURES ON SKELETAL NICKEL CATALYSTS

Results of the hydrogenation process of isoprene and piperylene mixtures, as well as their mixtures on multicomponent skeletal nickel catalysts are reported in this article. Hydrogenation of piperylene and isoprene proceeds at a higher rate (W=215-220 cm3/min·g Ni) on Ni-Mo-Cu alloy catalyst than on skeletal nickel (W=112-115 cm3/min·g Ni). The results of chromatographic analysis indicate that the hydrogenation of piperylene proceeds with high selectivity. The selectivity coefficient Кs is 0.95 and 0.98 on skeletal nickel and Ni-Mo-Cu catalyst, respectively. At hydrogenation of the piperylene-isoprene mixture the piperylene conversion rate (P > J) is prevailed. At piperylene conversion degree P=50 % the isoprene J conversion is 35-37 % on Renea Nickel. 34 % on Ni-Mo-Cu catalyst. The selectivity degree of hydrogenation of this mixture is Sp-i = 0.34-0.36 on Renea Nickel, Sp-i = 0.40 on Ni-Mo-Cu. It was found that during hydrogenation of piperylene and isoprene mixtures on Ni-Al-Mo-Cu (42-50-3-5 %) catalysts the mono- and disubstituted acetylenes are saturated with a high degree of conversion compared with isoprene.

Selective Monoborylation of Methane by a Mono Bipyridyl‐Nickel(II) Hydride Catalyst

We report the development of an earth‐abundant metal catalyst for methane C‒H borylation. The post‐synthetic metalation of bipyridine‐functionalized zirconium metal−organic framework (MOF) with NiBr2, followed by treatment of NaEt3BH affords MOF‐supported monomeric bipyridyl‐nickel(II) dihydride species via active site isolation. The heterogeneous and recyclable nickel catalyst selectively borylates methane at 200 ºC using pinacolborane (HBpin) to afford CH3Bpin in 61% yield with a turnover number (TON) up to 1388. The confinement of the active NiH2‐species within the uniformly porous MOF allows selective monoborylation of methane via shape‐selective catalysis by preventing the formation of sterically encumbered overborylated products. Unlike MOF‐Ni catalyst, its homogeneous control is almost inactive in methane borylation due to its intermolecular decomposition. Our mechanistic investigation, including spectroscopic, kinetic, and control experiments, as well as DFT calculations, revealed that stabilizing mononuclear bipyridyl‐nickel dihydride and diboryl species by MOF is crucial for achieving efficient methane borylation via turnover‐limiting σ‐bond metathesis. This work shows promise in designing MOF‐based abundant metal catalysts for the chemoselective functionalization of methane and other inert molecules into valuable chemicals.

Selective Monoborylation of Methane by a Mono Bipyridyl-Nickel(II)Hydride Catalyst.

We report the development of an earth-abundant metal catalyst for methane C‒H borylation. The post-synthetic metalation of bipyridine-functionalized zirconium metal-organic framework (MOF) with NiBr2, followed by treatment of NaEt3BH affords MOF-supported monomeric bipyridyl-nickel(II) dihydride species via active site isolation. The heterogeneous and recyclable nickel catalyst selectively borylates methane at 200 ºC using pinacolborane (HBpin) to afford CH3Bpin in 61% yield with a turnover number (TON) up to 1388. The confinement of the active NiH2-species within the uniformly porous MOF allows selective monoborylation of methane via shape-selective catalysis by preventing the formation of sterically encumbered overborylated products. Unlike MOF-Ni catalyst, its homogeneous control is almost inactive in methane borylation due to its intermolecular decomposition. Our mechanistic investigation, including spectroscopic, kinetic, and control experiments, as well as DFT calculations, revealed that stabilizing mononuclear bipyridyl-nickel dihydride and diboryl species by MOF is crucial for achieving efficient methane borylation via turnover-limiting σ-bond metathesis. This work shows promise in designing MOF-based abundant metal catalysts for the chemoselective functionalization of methane and other inert molecules into valuable chemicals.

Sequential One-Pot Transformation to R-CF2-Embedded 1,5-Diketones Enabled by Nickel: Access to 4-Perfluoroalkylpyridines.

Herein, we have demonstrated the application of bench-stable polyfluorinated alcohols as fluoroalkylating reagents for a sequential one-pot transformation with ketones to R-CF2-embedded 1,5-diketones and pyridines enabled by a nickel catalyst. The protocol is tolerant to a range of functional groups (>31 examples and up to 85% yield) and perfluoro alcohols and releases H2 and H2O as byproducts. Preliminary mechanistic studies, EPR analyses, and deuterium scrambling experiments were performed, and observed PC-H/PC-D = 2.12.

Novel photoresponsive dinuclear nickel catalysts for ethylene (co)polymerization

Novel photoresponsive dinuclear nickel catalysts for ethylene (co)polymerization

Green Diesel Production Through Deoxygenation Reaction with Natural Zeolite-supported Nickel and Copper Catalyst

The depletion of fossil fuels and their environmental impact necessitate sustainable alternatives. Green diesel, a biofuel with a chemical structure similar to conventional diesel, has gained traction as a viable alternative. This study explores the development of a cost-effective catalyst for green diesel production using deoxygenation. Deoxygenation refers to a broad class of chemical reactions where oxygen atoms are stripped from a molecule. This research employed abundant Indonesian natural zeolite (NZ) as a catalyst support, impregnated with non-noble metals, nickel (Ni), and copper (Cu). The investigation revealed that the NiCu/NZ catalyst achieved the highest oleic acid conversion (90.40%) and green diesel yield. The product distribution, ranging from C15 to C18 hydrocarbons, reflects the moderate acidity of the catalyst, promoting diverse cracking patterns compared to highly acidic catalysts. Additionally, the high specific surface area of NZ facilitates the conversion and good product distribution. Furthermore, the optimization process demonstrated that increasing hydrogen pressure during deoxygenation enhances both conversion rate and green diesel production.

Single-atom catalysts (SACs) for CO2 to CO conversion using cu, ni, and co on graphene flakes support; a DFT study

In this study, to convert the CO2 to more useful compound and in order to design the appropriate catalyst for this conversion, a graphene flakes support was considered for three transition metals of the 3d series (Cu, Co and Ni) as single-atom catalysts. Although different spin multiplicities for cobalt and nickel catalysts are possible, their relative energies and frontier orbital properties suggested the catalyst with the higher spin multiplicity is more suitable for this purpose. Moreover, to develop the mechanism of this conversion, two mechanistic routes were designed for the reaction and the structures of all reactants, products, intermediates and transition states of these routes were optimized and their enthalpies and Gibbs free energies were extracted. The final data showed that by the gas phase calculation, copper and cobalt are more favorable than nickel catalyst; copper is thermodynamically favorable and cobalt is kinetically favorable. The solvent effects were also considered using water and PCM methods, which showed, the solvent facilitate the reaction, especially for cobalt; therefore, in the solvent cobalt (and then, copper) is the most appropriate catalyst by both thermodynamic and kinetic data.

Nickel-Catalyzed Enantioconvergent Allenylic Amination of Allenols Activated by Hydrogen-Bonding Interaction with Methanol.

The ubiquitous nature of amines in drug compounds, bioactive molecules and natural products has fueled intense interest in their synthesis. Herein, we introduce a nickel-catalyzed enantioconvergent allenylic amination of methanol-activated allenols. This protocol affords a diverse array of functionalized allenylic amines in high yields and with excellent enantioselectivities. The synthetic potential of this method is demonstrated by employing bioactive amines as nucleophiles and conducting gram-scale reactions. Furthermore, mechanistic investigations and DFT calculations elucidate the role of methanol as an activator in the nickel-catalyzed reaction, facilitating the oxidative addition of the C-O bond of allenols through hydrogen-bonding interactions. The remarkable outcomes arise from a rapid racemization of allenols enabled by the nickel catalyst and from highly enantioselective dynamic kinetic asymmetric transformation of η3-alkadienylnickel intermediates.

Metal‐Catalyzed Polymer Dehydrochlorination and Hydrodefluorination

AbstractDehydrochlorination (DHC) is of importance for modulating the physical properties of halogenated polymers. In this work, the DHC of commercial VDF‐CTFE (vinylidene fluoride‐co‐chlorotrifluoroethylene) (10 mol % CTFE) copolymer to VDF‐DB (vinylidene fluoride with unsaturated moieties‐Double Bond) was achieved in mild reaction conditions (150 °C and 3 bar hydrogen) using different supported nickel catalysts. A complete DHC was observed within four hours of the reaction. Additionally, a certain extent (8–35 %) of hydrodefluorination (HDF) of the polymer, a challenging transformation, can also be achieved after 72 hours. A plausible mechanism based on the nuclear magnetic resonance (NMR) spectroscopy study of DHC and HDF of VDF‐CTFE was proposed. The catalyst was recyclable and stable against leaching after at least three cycles.

Quantum confinement for stable nickel catalyst in hydrogen oxidation

Quantum confinement for stable nickel catalyst in hydrogen oxidation