Clean and Efficient Transformation of CO2 to Isocyanic Acid: The Important Role of Triatomic Cation ScNH+

Conversion of Carbon Dioxide into a Series of CBxOy- Compounds Mediated by LaB3,4O2- Anions: Synergy of the Electron Transfer and Lewis Pair Mechanisms to Construct B-C Bonds

Converting CO2 into value-added products containing B-C bonds is a great challenge, especially for multiple B-C bonds, which are versatile building blocks for organoborane chemistry. In the condensed phase, the B-C bond is typically formed through transition metal-catalyzed direct borylation of hydrocarbons via C-H bond activation or transition metal-catalyzed insertion of carbenes into B-H bonds. However, excessive amounts of powerful boryl reagents are required, and products containing B-C bonds are complex. Herein, a novel method to construct multiple B-C bonds at room temperature is proposed by the gas-phase reactions of CO2 with LaBmOn- (m = 1-4, n = 1 or 2). Mass spectrometry and density functional theory calculations are applied to investigate these reactions, and a series of new compounds, CB2O2-, CB3O3-, and CB3O2-, which possess B-C bonds, are generated in the reactions of LaB3,4O2- with CO2. When the number of B atoms in the clusters is reduced to 2 or 1, there is only CO-releasing channel, and no CBxOy- compounds are released. Two major factors are responsible for this quite intriguing reactivity: (1) Synergy of electron transfer and boron-boron Lewis acid-base pair mechanisms facilitates the rupture of C═O double bond in CO2. (2) The boron sites in the clusters can efficiently capture the newly formed CO units in the course of reactions, favoring the formation of B-C bonds. This finding may provide fundamental insights into the CO2 transformation driven by clusters containing lanthanide atoms and how to efficiently build B-C bonds under room temperature.

Dinitrogen and Carbon Dioxide Activation to Form C-N Bonds at Room Temperature: A New Mechanism Revealed by Experimental and Theoretical Studies

In light of the current energy requirements, the conversion of CO₂ and N₂ into useful C-N bond-containing products under mild conditions has become an area of intense research. However, the inert nature of N₂ and CO₂ renders their coupling extremely challenging. Herein, nitrogen and carbon atoms originating from N₂ and CO₂, respectively, are fixed sequentially by NbH₂^- anions in the gas phase at room temperature. Isocyanate and NbO₂CN^- anions were formed under thermal collision conditions, thus achieving the formation of new C-N bonds directly from simple N₂ and CO₂. The anion structures and reaction details were studied by mass spectrometry, photoelectron spectroscopy, and quantum chemical calculations. A novel N₂ activation mode (metal-ligand activation, MLA) and a related mechanism for constructing C-N bonds mediated by a single non-noble metal atom are proposed. In this MLA mode, the C atom originating from CO₂ serves as an electron reservoir to accept and donate electrons.

Oxidation of isoprene by titanium oxide cluster cations in the gas phase

The heterogeneous oxidation of isoprene (C5H8) by metal-oxide particles, such as the typical mineral aerosols TiO2, plays an important role in the isoprene atmospheric chemistry. However, the underlying mechanism of C5H8 oxidation remains elusive owing to the complexities of aerosol surfaces and reaction channels. Herein, we report the gas-phase reactions of TixOy+ (x = 1-7, y = 1-14) cations with isoprene by using mass spectrometry and density functional theory (DFT) calculations. Five types of reaction channels were observed: association, hydrogen atom transfer (HAT), C-C bond cleavage, combined oxygen atom transfer (OAT) and HAT and combined OAT and C-C bond cleavage. It is noteworthy that formaldehyde is known as the major oxidation product of isoprene/hydroxyl radicals in the atmosphere. In addition, CO has not been observed in the reactions of isoprene with gas-phase ions. Therefore, the reaction mechanisms of CH2O and CO generation observed in Ti2O5+/C5H8 and Ti4O8+/C5H8 systems were further investigated by DFT calculations, and the calculated results are in agreement with the experimental observations. In these two reactions, both Ti and O atoms can be the adsorption sites for C5H8. The reaction channels and mechanistic information gained in these gas-phase model reactions may offer fundamental insights relevant to the corresponding oxidation processes over titanium oxide aerosols in the atmosphere.

Nb2BN2− cluster anions reduce four carbon dioxide molecules: reactivity enhancement by ligands

The thermal gas-phase reactions of Nb₂BN₂⁻ cluster anions with carbon dioxide have been explored by using the art of time-of-flight mass spectrometry and density functional theory calculations.

Efficient Liberation of Ammonia from Thermal Reaction of ScNH+ Cations and Water

Ammonia synthesis by using water as a hydrogen source is a challenging task. Laser-ablation-generated ScNH⁺ cations have been mass-selected using a quadrupole mass filter and reacted with H₂O in a linear ion trap reactor under thermal collision conditions. Through mass spectrometry in conjunction with density functional theory calculations, we found that ammonia is released as the product in the reaction of ScNH⁺ with H₂O, and this reaction is with high efficiency and selectivity, and the rate constant for the reaction is (1.14 ± 0.23) × 10^-10 cm³ molecule^-1 s^-1, corresponding to the reaction efficiency of 15%. Metal imido complexes (*MNH) are one of the important intermediates in the currently reported NH₃ synthetic reactions. The gas-phase ScNH⁺ cation can be a simplified model of *MNH over catalysts of NH₃ synthesis, and the facile proton transfer mechanism obtained in this model system may offer fundamental mechanistic insights into how to design catalysts for ammonia production by using water as the hydrogen source under ambient conditions.