Complete cleavage of the N≡N triple bond by Ta<sub>2</sub>N<sup>+</sup>via degenerate ligand exchange at ambient temperature: A perfect catalytic cycle

Chai

et al. 2021

Sci Rep

This paper reports on the gas-phase amination reaction of aromatic hydrocarbons occurring under corona discharge conditions with N2 gas as the nitrogen source. The corona discharge device within an atmospheric pressure chemical ionization source was employed to achieve the plasma-assisted N2 fixation, and the coupled ion trap mass spectrometer (IT-MS) was used to detect positively charged product ions. In the model case, under APCI conditions, unusual product ions, [M + 16]+ and [M + 14]+, were observed. Based on the high resolution MS data and tandem mass spectrometric information, [M + 16]+ was confirmed to be protonated p-toluidine and [M + 14]+ was confirmed to be p-methylphenylnitrenium ion. According to the experimental results of the isotopic labelling and substituent effect, one feasible mechanism is proposed as follows. Firstly, N2 is activated by plasma caused via the corona discharge and then electrophilically attacks toluene, yielding the key intermediate, p-methylphenylnitrenium; secondly, the intermediate undergoes double-hydrogen transfer reaction to give rise to the final product ion, protonated p-toluidine. This study may provide a novel idea to explore new and green method for the synthesis of anilines.

Section: Introductionmentioning

confidence: 99%

Gas-phase amination of aromatic hydrocarbons by corona discharge-assisted nitrogen fixation

Chai

et al. 2021

Sci Rep

Proc. Natl. Acad. Sci. U.S.A.

“…Connecting two molecules in a specific manner is a substantial challenge, if the new bond that is formed has to substitute inert bonds in the reagents (1). Synthetic strategies to achieve this goal usually involve complex multistep processes, and the initial bond activation is often based on catalysis using reactive metal centers (2)(3)(4)(5)(6). It would be transformative if one could take a stable molecule, break a specific bond, and form a highly reactive undercoordinated binding site, which subsequently is connected to another molecule of choice.…”

mentioning

confidence: 99%

Direct functionalization of C−H bonds by electrophilic anions

Warneke

Mayer

Rohdenburg

et al. 2020

Alkanes and [B12X12]2− (X = Cl, Br) are both stable compounds which are difficult to functionalize. Here we demonstrate the formation of a boron−carbon bond between these substances in a two-step process. Fragmentation of [B12X12]2− in the gas phase generates highly reactive [B12X11]− ions which spontaneously react with alkanes. The reaction mechanism was investigated using tandem mass spectrometry and gas-phase vibrational spectroscopy combined with electronic structure calculations. [B12X11]− reacts by an electrophilic substitution of a proton in an alkane resulting in a B−C bond formation. The product is a dianionic [B12X11CnH2n+1]2− species, to which H+ is electrostatically bound. High-flux ion soft landing was performed to codeposit [B12X11]− and complex organic molecules (phthalates) in thin layers on surfaces. Molecular structure analysis of the product films revealed that C−H functionalization by [B12X11]− occurred in the presence of other more reactive functional groups. This observation demonstrates the utility of highly reactive fragment ions for selective bond formation processes and may pave the way for the use of gas-phase ion chemistry for the generation of complex molecular structures in the condensed phase.

“…This finding constitutes one more example of the Mars‐van Krevelen (MvK) mechanism, [41–46] a term that belongs to the basic concepts of heterogeneous catalysis, [46] although the experiments performed here lie within the scope of homogeneous catalysis. The reaction between Sc + and SO 2 is found to belong to the very rare cases in which the catalytically active species, namely the [ScO] + oxide cation, can be identified [46] . Moreover, [ScO] + is, in the best sense, a prime example of a catalyst that emerges seemingly unchanged after the reaction has been completed.…”

Section: Introductionmentioning

confidence: 86%

Experiment and Theory Clarify: Sc⁺ Receives One Oxygen Atom from SO₂ to Form ScO⁺, which Proves to be a Catalyst for the Hidden Oxygen‐Exchange with SO₂

et al. 2022

Self Cite

Using Fourier‐transform ion cyclotron resonance mass spectrometry, it was experimentally determined that Sc+ in the highly diluted gas phase reacts with SO2 to form ScO+ and SO. By 18O labeling, ScO+ was shown to play the role of a catalyst when further reacting with SO2 in a Mars‐van Krevelen‐like (MvK) oxygen exchange process, where a solid catalyst actively reacts with the substrate but emerges apparently unchanged at the end of the cycle. High‐level quantum chemical calculations confirmed that the multi‐step process to form ScO+ and SO is exoergic and that all intermediates and transition states in between are located energetically below the entrance level. The reaction starts from the triplet surface; although three spin‐crossing points with minimal energy have been identified by computational means, there is no evidence that a two‐state scenario is involved in the course of the reaction, by which the reactants could switch from the triplet to the singlet surface and back. Pivotal to the oxygen exchange reaction of ScO+ with SO2 is the occurrence of a highly symmetric four‐membered cyclic intermediate by which two oxygen atoms become equivalent.