Cleavage Of Triple Bond Research Articles

Synergistic N/F Dual-Doped MoC/C Catalyst Synthesized via Liquid Phase Plasma for Sustainable Ammonia Production.

NH3 is a versatile solution for the storage and distribution of sustainable energy, offering high energy density and promising applications as a renewable hydrogen carrier. However, electrochemical NH3 synthesis under ambient conditions remains challenging, such as low selectivity and efficiency, owing to the inertness of N≡N and competing reactions. In this study, a catalyst (MoC/NFC) comprising molybdenum carbide evenly dispersed on carbon doped with N and F heteroatoms was successfully synthesized using liquid-phase plasma. The MoC/NFC catalyst exhibited a maximum NH3 yield of 115 μg h-1 mg-1cat. with a faradaic efficiency of 1.15% at -0.7 V vs reversible hydrogen electrode in 0.1 M KOH electrolyte. Pyridinic- and pyrrolic-N atoms adjacent to the carbon pores served as active sites for N2 adsorption and enabled N2 triple bond cleavage. In addition, F doping contributed to N2 activation owing to the high electronegativity of 3.98, resulting in the attraction of more electrons. These findings demonstrate a significant advancement in the development of efficient catalysts for electrochemical ammonia synthesis, potentially paving the way for scalable and sustainable NH3 production methods that can support the growing demand for renewable energy storage solutions.

Novel Methods for the Formation of Free Carbyne Radicals in Solution.

Carbyne free radicals RC⋮ (RC) are usually associated with high-energy processes, thus research on their preparation, chemical reactivity, and prevalence under mild conditions is scarce. Recently, it was reported that metallo-complexes containing CR ligands may undergo spontaneous degradation in aqueous solutions to produce free RC radicals. These highly reactive species may react with each other to form the corresponding alkyne and other products. The reaction of 1,1,1 halo-carbo-hydrates with Cr(II) ions also forms RC radicals under mild conditions. Herein, we report two additional synthetic routes that produce free RC radicals under mild conditions. First, the reaction between metallic zinc and acetic anhydride produces 2-butyne and several other C2, C3, and C4 compounds. Isotopic-labeling experiments indicate that the formation of 2-butyne results from an inter-molecular reaction in which two RC moieties from two acetic anhydride molecules combine in solution. In addition, the degradation of the tri-molybdenum complex [Mo3(H3CC≡CCH3)(OAc)(H2O)2Br7], in which a 2-butyne ligand is coordinated to the Mo3 framework in a μ3-η2 (⊥) binding mode in aqueous solution produces several C2, C3, C4 and C5 molecules. This indicates the formation of free CH3C radicals by a homolytic cleavage of the carbon-carbon triple bond.

Ru(II)-Catalyzed Deoxygenative Formal [3 + 1 + 2] Benzannulation of Allyl Alcohols and Acetylenediesters via C-H Activation and Selective Carbon-Carbon Triple Bond Cleavage.

An unprecedented Ru(II)-catalyzed deoxygenative, site-selective formal [3 + 1 + 2] benzannulation reaction for the efficient synthesis of highly substituted benzene molecules is reported. This reaction between allyl alcohols and acetylenedicarboxylate esters proceeds via cascade C-H activation, consecutive double migratory insertion with alkynes, and cycloaromatization followed by an unusual specific C-C triple bond cleavage.

Nonadiabatic quantum dynamics explores non-monotonic photodissociation branching of N2 into the N(4S) + N(2D) and N(4S) + N(2P) product channels.

Vacuum ultraviolet (VUV) photodissociation of N2 molecules is a source of reactive N atoms in the interstellar medium. In the energy range of VUV optical excitation of N2, the N-N triple bond cleavage leads to three types of atoms: ground-state N(4S) and excited-state N(2P) and N(2D). The latter is the highest reactive and it is believed to be the primary participant in reactions with hydrocarbons in Titan's atmosphere. Experimental studies have observed a non-monotonic energy dependence and non-statistical character of the photodissociation of N2. This implies different dissociation pathways and final atomic products for different wavelength regions in the sunlight spectrum. We here apply ab initio quantum chemical and nonadiabatic quantum dynamical techniques to follow the path of an electronic state from the excitation of a particular singlet 1Σ+u and 1Πu vibronic level of N2 to its dissociation into different atomic products. We simulate dynamics for two isotopomers of the nitrogen molecule, 14N2 and 14N15N for which experimental data on the branching are available. Our computations capture the non-monotonic energy dependence of the photodissociation branching ratios in the energy range 108 000-116 000 cm-1. Tracing the quantum dynamics in a bunch of electronic states enables us to identify the key components that determine the efficacy of singlet to triplet population transfer and therefore predissociation lifetimes and branching ratios for different energy regions.

BN Analogue of Butadiyne: A Platform for Dinitrogen Release and Reduction.

Exploration of the metallomimetic chemistry of main group elements is of the utmost importance from the perspective of both fundamental research and potential applications. Here, we report the synthesis, bonding analysis, and reactivities of an isolable diiminoborane, Mes*B≡N─N≡BMes* (Mes* = 2,4,6-tri-tert-butylphenyl) (1), a BN analogue of butadiyne. This species is characterized by a conjugated B≡N─N≡B moiety, a structural feature that enables the controlled release of N2 when it is exposed to organic nitriles. Furthermore, the N2 unit in 1 could be reduced to an ammonium salt via cleavage of the BN triple bond. Our work shows a rare example of an unsaturated BN system, serving as a platform for both the release and reduction of N2. This discovery opens new pathways and holds substantial influence on the future design of functional main group N2 species.

Unanticipated switch of reactivity of isonitrile via N≡C bond scission: Cascade formation of symmetrical sulfonyl guanidine

Unanticipated formation of symmetrical sulfonyl guanidine was observed while treating isonitriles with N,N-dibromoarylsulfonamides in absence of an external amine source. Interesting feature of this work is that one molecule of isonitrile initially reacts with dibromoarylsulfonamide via the C-end to produce the intermediate carbodiimide while the other molecule undergoes C≡N triple bond cleavage to react as amine source with the intermediate. This switch of reactivity from C-center to N-center of the isonitrile generated symmetrical guanidine.

Regiodivergent Synthesis of Densely Functionalized Indolizines via (2 + 2 + 1) Cycloaddition.

A novel metal and additive free, atom-economic method for the regiodivergent synthesis of crucial 6- or 8-substituted indolizine from meta-amide-substituted pyridine and alkyne via a [2 + 2 + 1] cycloaddition is developed. The reaction proceeds through the cleavage of the carbon-carbon triple bond. The synthesized product contains an important amide group that can be further functionalized to afford biologically active compounds.

Green synthesis of ammonia from steam and air using solid oxide electrolysis cells composed of ruthenium‐modified perovskite catalyst

AbstractThe green electrochemical synthesis of ammonia (NH3) through solid electrolysis has been intensively investigated. This research reported an improvement of NH3 production rate using in situ exsolution of ruthenium (Ru) atoms into lanthanum strontium chromium ferrite perovskite (LaxSr1−xCryFe1−yO3−δ) catalyst. The in situ Ru exsolution was achieved by reducing the optimized stoichiometric La0.33Sr0.67Cr0.33Fe0.52Ru0.15O3−δ (LSCrFRu) powders obtained in 10‐vol% H2/Ar at 800°C for 1.0 h. These Ru nanoparticles (NPs) were embedded on the surface of the LSCrFRu matrix, evenly distributed with a size varying from 4.4 ± 0.5 nm. With the exsolution of Ru atoms, greater oxygen vacancies were formed in ex‐LSCrFRu and gadolinium‐doped ceria (GDC) composite than those in LSCrF‐GDC electrocatalyst, beneficial to N2 gas adsorption and triple bond cleavage. These Ru‐modified LSCrFRu‐GDC catalysts showed a synthesis rate of 4.73 × 10−10 mol s−1 cm−2 at 550°C under 1.6 V, doubling the rate using LSCrF‐GDC catalyst. The improved ammonia synthesis kinetic is mainly attributed to embedded Ru NPs and the increased oxygen vacancies formed during the in situ exsolution process. More active sites and higher activity for H2O and N2 adsorption and activation collectively advanced facile transportation of O2− that further promotes the cleavage of covalent bonds in H2O, providing more H+ for the hydrogenation in the nitrogen reduction reaction. This research will open a new paradigm for the electrochemical synthesis of ammonia with mitigating the drawbacks of traditional NH3 production.

Conversion of Dinitrogen and Oxygen to Nitric Oxide Mediated by Triatomic Yttrium Cations: Reversible N-N Bond Switching.

The direct coupling of dinitrogen (N2) and oxygen (O2) to produce value-added chemicals such as nitric acid (HNO3) at room temperature is fascinating but quite challenging because of the inertness of N2 molecules. Herein, an interesting reaction pathway is proposed for a direct conversion of N2 and O2 mediated by all-metal Y3+ cations. This reaction pattern begins with the N≡N triple bond cleavage by Y3+ to generate a dinitride cation Y2N2+, and the electrons that lead to N2 activation in this process mainly originate from Y atoms. In the following consecutive reactions with two O2 molecules, the electrons stored in the N atoms are gradually released to reduce O2 through re-formation and re-fracture of the N-N bonds, with concomitant release of two NO molecules. Therefore, the reversible N-N bond switching acts as an efficient electron reservoir to drive the oxidation of the reduced N atoms, leading to the formation of NO molecules. This method of producing NO by direct coupling N2 and O2 molecules, which is the reversible N-N bond switching, may provide a new strategy for the direct synthesis of HNO3, etc.

Solvent-Dependent Selective Synthesis of CF3-Tethered Indazole Derivatives Based on Multiple Bond Activations

Presented herein is a solvent-dependent selective synthesis of CF3-tethered indazole derivatives via the cascade reactions of 1-arylpyrazolidinones with trifluoromethyl ynones. Mechanistically, the formation of the title products involves cascade N-H/C-H/C-N/C-C bond cleavage along with pyrazole ring formation and pyrazolidinone ring opening. For the formation of a pyrazole scaffold, 1-phenylpyrazolidinone acts as a C2N2 synthon, while trifluoromethyl ynone serves as a C1 synthon. Meanwhile, trifluoromethyl ynone also acts as an enol unit to facilitate the ring opening of the pyrazolidinone ring and provide a trifluoropropenoxy fragment via cleavage of the alkynyl triple bond and migration of the cleaved moiety. When the reaction was run in trifluoroethanol instead of DCE, it selectively afforded indazole derivatives tethered with a trifluoroethoxy moiety through in situ transesterification. To our knowledge, this is the first synthesis of CF3-tethered indazole derivatives via concurrent alkynyl activation, pyrazole formation, and CF3 migration.

Unusual cleavage of phosphaalkynes triple bond in the coordination sphere of transition metals.

The reaction of RCP (R = Me, tBu, iPr) with Co2(CO)8 and Fe2(CO)9 under mild conditions led to unpredictable fragmentations of the CP triple bond and subsequent formation of clusters with a dimeric Co3E (E = P and RC) and an Fe3P(CR) core, respectively.

Self-supported Mo-doped TiO2 electrode for ambient electrocatalytic nitrogen oxidation

Electrocatalytic nitrogen oxidation reaction (NOR) provides an eco-friendly pathway for ambient N2 fixation and nitrate/nitric acid synthesis but is plagued by sluggish kinetics due to the weak adsorption of N2 molecules and cleavage of NN triple bonds. Herein, a self-supported Mo-doped TiO2 electrode prepared by one-step hydrothermal method is reported for efficient nitrogen oxidation. Electrochemical measurements and spectroscopy investigations reveal that the inert TiO2 is effectively triggered by Mo substitution in terms of enhanced N2 adsorption and activation. As further confirmed by density function theory calculations, the incorporation of Mo reduces the barrier of the rate-determining step and provides an energetically favorable NOR pathway compared to pristine rutile TiO2. Electrochemical results show that Mo-doped TiO2 electrode achieves a nitrate yield of 5.44 μg h−1 mgcat−1 (or 8.77 ± 0.39 nmol h−1 cm−2) with a Faradaic efficiency of 2.88%. The formation of nitrate from N2 under positive bias is further demonstrated by in situ ultraviolet-visible spectrophotometry. This work provides experimental and theoretical evidences that Mo doping can stimulate the stable yet electrocatalytically inert Ti-based oxide toward NOR via promoting active sites formation and lowering activation energy barriers.

Acid‐Promoted Carbon‐Carbon Triple Bond Cleavage of Ynones for the Synthesis of Benzo[d]oxazoles/Benzo[d]thiazoles and 1‐Arylethan‐1‐ones

AbstractA synchronous synthesis of benzo[d]oxazoles/benzo [d]thiazoles and 1‐arylethan‐1‐ones enabled by acid‐promoted C−C triple bond cleavage of ynones is disclosed. This reaction was accomplished with good tolerance of various functional groups and aminophenols/aminobenzenethiols to access the corresponding products, especially some structurally special 1‐arylethan‐1‐ones, in moderate to good yield. Furthermore, the readily accessible synthesis of some biologically active molecules has highlighted the synthetic utility of this strategy.

Copper-Catalyzed Nitrogen Atom Transfer to Isoquinolines via C-N Triple Bond Cleavage and Three-Component Cyclization.

A copper(I)-catalyzed tandem reaction of 2-bromoaryl ketones, terminal alkynes, and CH3CN is developed, which combines N atom transfer and three-component [3 + 2 + 1] cyclization, and efficiently produces densely functionalized isoquinolines in a facile, highly selective, and general manner. In the reaction, the formation of aromatic C-N bonds along with the complete C-N triple bond cleavage is first realized; Cu(III)-acetylide species might serve as the intermediates, which allow highly selective 6-endo-dig cyclization.

(n-Bu)4NBr-Promoted N2 Splitting to Molybdenum Nitride.

Splitting of N2 via six-electron reduction and further functionalization to value-added products is one of the most important and challenging chemical transformations in N2 fixation. However, most N2 splitting approaches rely on strong chemical or electrochemical reduction to generate highly reactive metal species to bind and activate N2, which is often incompatible with functionalizing agents. Catalytic and sustainable N2 splitting to produce metal nitrides under mild conditions may create efficient and straightforward methods for N-containing organic compounds. Herein, we present that a readily available and nonredox (n-Bu)4NBr can promote N2-splitting with a Mo(III) platform. Both experimental and theoretical mechanistic studies suggest that simple X- (X = Br, Cl, etc.) anions could induce the disproportionation of MoIII[N(TMS)Ar]3 at the early stage of the catalysis to generate a catalytically active {MoII[N(TMS)Ar]3}- species. The quintet MoII species prove to be more favorable for N2 fixation kinetically and thermodynamically, compared with the quartet MoIII counterpart. Especially, computational studies reveal a distinct heterovalent {MoII-N2-MoIII} dimeric intermediate for the N≡N triple bond cleavage.

Titanomagnetite functionalized by amino acid-based ionic liquid and cobalt (Fe3-xTixO4-SiO2@TrpBu3+I−-Co(II)): A reusable bio-nanocomposite for the synthesis of aryl thioamides

An efficient and straightforward three-component reaction of alkynes (terminal and internal), elemental sulfur, and amides using novel bio-nanocomposite is described. The bio-nanostructure obtained from step-by-step coating the titanomagnetite core by silica, N,N,N-tributyltryptophanium iodide ionic liquid, and cobalt respectively. The Fe3-xTixO4-SiO2@TrpBu3+I−-Co(II) characterized though FT-IR, FESEM, EDAX, XRF, TGA/DTG, VSM, and XPS techniques. Its catalytic efficacy examined successfully in the solvent-free three-component reaction of alkynes (terminal and internal), S8, and amides to prepare the corresponding aryl thioamides via the CC triple bond cleavage. The reusability examination of the Fe3-xTixO4-SiO2@TrpBu3+I−-Co(II) bio-nanocomposite proceeded successfully within two runs. The recovered nanostructure characterized through EDAX and FESEM techniques that demonstrated no significant changes in the morphology and constitutive elements.

Iridium Dimer Anion-Mediated C≡C Triple Bond Cleavage and Successive Dehydrogenation of Acetylene in the Gas Phase.

The reactions of the iridium dimer anion [Ir2]- with acetylene have been studied by mass spectrometry in the gas phase, which indicate that the [Ir2]- anion can consecutively react with C2H2 molecules to form the [Ir2C2x]- (x = 1, 2) and [Ir2C2yH2]- (y = 3-5) anions as major products with the successive release of H2 molecules at room temperature. The reactions are confirmed by the reactions of the mass-selected product [Ir2C2]- anion with C2H2 to produce [Ir2C4]- and [Ir2C2yH2]- (y = 3-5). Photoelectron spectra and quantum chemistry calculations confirm that the [Ir2C2x]- (x = 1, 2) product anions possess cyclic [Ir(μ-C)2Ir]- and [Ir(μ-C)(μ-C3)Ir]- structures, implying that the robust C≡C triple bond of acetylene can be completely cleaved by the [Ir2]- anion.

3.4% Solar‐to‐Ammonia Efficiency from Nitrate Using Fe Single Atomic Catalyst Supported on MoS2 Nanosheets

AbstractElectrochemical synthesis of NH3 is a carbon‐free alternative to the traditional Haber–Bosch process. Obtaining NH3 from environmental pollutants, such as nitrates or nitrites, is a more practical route than from the nitrogen reduction reaction (NRR) due to the difficult cleavage of the inert triple bond of nitrogen gas. Here, a novel heterogeneous catalyst is reported based on iron (Fe) single‐atoms supported on 2D MoS2 (Fe‐MoS2) for the nitrate reduction reaction (NO3RR). Fe‐MoS2 exhibits remarkable performance with a maximum Faradaic efficiency of 98% for NO3RR to NH3 at an onset potential of −0.48 V versus the reversible hydrogen electrode (RHE) as confirmed by the isotopic nuclear magnetic resonance (NMR) analyses. Density functional theory (DFT) calculations reveal that the enhanced selectivity for the production of NH3 from single Fe atoms supported on MoS2 is attributed to a reduced energy barrier of 0.38 eV associated with de‐oxidation of *NO to *N. The catalysts are coupled to an InGaP/GaAs/Ge triple‐junction solar cell to demonstrate a solar‐to‐ammonia (STA) conversion efficiency of 3.4% and a yield rate of 510 µg h−1 cm−2. The results open new avenues for the design of single‐atom catalysts (SAC) for the realization of solar‐driven ammonia production.

Palladium-Catalyzed Cascade Carbonylation to α,β-Unsaturated Piperidones via Selective Cleavage of Carbon-Carbon Triple Bonds.

A direct and selective synthesis of α,β‐unsaturated piperidones by a new palladium‐catalyzed cascade carbonylation is described. In the presented protocol, easily available propargylic alcohols react with aliphatic amines to provide a broad variety of interesting heterocycles. Key to the success of this transformation is a remarkable catalytic cleavage of the present carbon–carbon triple bond by using a specific catalyst with 2‐diphenylphosphinopyridine as ligand and appropriate reaction conditions. Mechanistic studies and control experiments revealed branched unsaturated acid 11 as crucial intermediate.

Atomically Dispersed Manganese Lewis Acid Sites Catalyze Electrohydrogenation of Nitrogen to Ammonia

Atomically Dispersed Manganese Lewis Acid Sites Catalyze Electrohydrogenation of Nitrogen to Ammonia