Coupling conversion of CO 2 and N 2 molecules under mild conditions to form useful N−C bond-containing products has attracted significant attention. However, the activation and direct coupling of such very inert molecules are quite challenging. Herein, we determined that this coupling reaction can be realized by AuNbBO − quaternary anions at room temperature. The well-defined AuNbBO − anions can cleave the NN bond in N 2 and two CO bonds in CO 2 to form a novel product NCNBO − . To the best of our knowledge, the NCNBO − anion has been experimentally synthesized for the first time by coupling N 2 and CO 2 . Comparative studies with Nb 2 BO − /N 2 and NbBO − /N 2 systems further indicate that the presence of a Au atom in AuNbBO − is indispensable for this N 2 and CO 2 coupling reaction, because the Au atom can decrease the active orbital energies of AuNbBO − anions to facilitate the π-back-donating interaction between AuNbBO − and N 2 .
The direct coupling of dinitrogen (N 2 ) and oxygen (O 2 ) to produce value-added chemicals such as nitric acid (HNO 3 ) at room temperature is fascinating but quite challenging because of the inertness of N 2 molecules. Herein, an interesting reaction pathway is proposed for a direct conversion of N 2 and O 2 mediated by all-metal Y 3 + cations. This reaction pattern begins with the N�N triple bond cleavage by Y 3 + to generate a dinitride cation Y 2 N 2 + , and the electrons that lead to N 2 activation in this process mainly originate from Y atoms. In the following consecutive reactions with two O 2 molecules, the electrons stored in the N atoms are gradually released to reduce O 2 through reformation 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 N 2 and O 2 molecules, which is the reversible N−N bond switching, may provide a new strategy for the direct synthesis of HNO 3 , etc.
We characterized the stationary points along the nucleophilic substitution (SN2), oxidative insertion (OI), halogen abstraction (XA), and proton transfer (PT) product channels of M− + CH3X (M = Cu, Ag, Au; X = F, Cl, Br, I) reactions using the CCSD(T)/aug-cc-pVTZ level of theory. In general, the reaction energies follow the order of PT > XA > SN2 > OI. The OI channel that results in oxidative insertion complex [CH3–M–X]− is most exothermic, and can be formed through a front-side attack of M on the C-X bond via a high transition state OxTS or through a SN2-mediated halogen rearrangement path via a much lower transition state invTS. The order of OxTS > invTS is inverted when changing M− to Pd, a d10 metal, because the symmetry of their HOMO orbital is different. The back-side attack SN2 pathway proceeds via typical Walden-inversion transition state that connects to pre- and post-reaction complexes. For X = Cl/Br/I, the invSN2-TS’s are, in general, submerged. The shape of this M− + CH3X SN2 PES is flatter as compared to that of a main-group base like F− + CH3X, whose PES has a double-well shape. When X = Br/I, a linear halogen-bonded complex [CH3−X∙··M]− can be formed as an intermediate upon the front-side attachment of M on the halogen atom X, and it either dissociates to CH3 + MX− through halogen abstraction or bends the C-X-M angle to continue the back-side SN2 path. Natural bond orbital analysis shows a polar covalent M−X bond is formed within oxidative insertion complex [CH3–M–X]−, whereas a noncovalent M–X halogen-bond interaction exists for the [CH3–X∙··M]− complex. This work explores competing channels of the M− + CH3X reaction in the gas phase and the potential energy surface is useful in understanding the dynamic behavior of the title and analogous reactions.
The transition metal dichalcogenides 1T -TaS2 and 1T -TaSe2 have been extensively studied for the complicated correlated electronic properties. The origin of different surface electronic states remains controversial. We apply scanning tunneling microscopy and spectroscopy to restudy the surface electronic state of bulk 1T -TaSe2. Both insulating and metallic states are identified in different areas of the same sample. The insulating state is similar to that in 1T -TaS2, concerning both the dI/dV spectrum and the orbital texture. With further investigations on single-step areas, the discrepancy of electronic states is found to be associated with different stacking orders. The insulating state is most possibly a single layer property, modulated to a metallic state in some particular stacking orders. The metallic spectrum and corresponding stacking orders are dominant in 1T-TaSe2, consistent with the metallic transport measurement. We then reconcile the bulk metallic and surface insulating state in 1T -TaSe2. The rich phenomena in 1T -TaSe2 deepens our understanding of the correlated electronic state on bulk 1T -TaSe2 and 1T -TaS2.
Halogen bonds (XBs) between metal anions and halides have seldom been reported because metal anions are reactive for XB donors. The pyramidal-shaped Mn(CO)5− anion is a candidate metallic XB acceptor with a ligand-protected metal core that maintains the negative charge and an open site to accept XB donors. Herein, Mn(CO)5− is prepared by electrospray ionization, and its reaction with CH3I in gas phase is studied using mass spectrometry and density functional theory (DFT) calculation. The product observed experimentally at m/z = 337 is assigned as [IMn(CO)4(OCCH3)]−, which is formed by successive nucleophilic substitution and reductive elimination, instead of the halogen-bonded complex (XC) CH3−I···Mn(CO)5−, because the I···Mn interaction is weak within XC and it could be a transient species. Inspiringly, DFT calculations predict that replacing CH3I with CF3I can strengthen the halogen bonding within the XC due to the electro-withdrawing ability of F. More importantly, in so doing, the nucleophilic substitution barrier can be raised significantly, ~30 kcal/mol, thus leaving the system trapping within the XC region. In brief, the combination of a passivating metal core and the introduction of an electro-withdrawing group to the halide can enable strong halogen bonding between metallic anion and iodide.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.