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

Abstract

Achieving the desired selective transformations of the very stable CO 2 into useful chemicals is quite important for the development of economically and environmentally sustainable synthetic methods. Herein, mass spectrometric experiments and quantum-chemical calculations have identified that ScNH + reacts quite efficiently with CO 2 under thermal collision conditions to exclusively yield ScO + and isocyanic acid (HNCO). This is a novel reaction type in CO 2 activation reactions mediated by gas-phase ions. In this reaction, the CN double bond has also been formed for the first time in the gas phase. The mechanism of "migratory insertion" is proposed. Coupled with the previously reported reaction of Sc + with NH 3 , HNCO can be synthesized under mild conditions from NH 3 and CO 2 in quite simple reactions. The mechanistic information gained in this gas-phase model reaction can offer fundamental insights relevant to corresponding processes and further guide on how to design brand new catalysts.

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

“…It is noteworthy that among these gas-phase − and aforementioned condensed-phase − examples, only multinuclear metal atoms are active sites except for the noble metal Os/N 2 system. Also, the N atoms originating from N 2 molecules are strongly bound to these metallic gas-phase species, and therefore no N-containing products can be released. − In addition, numerous studies on CO 2 activation and transformations mediated by gas-phase metal-containing ions have been reported. − Generally, the nitrogen source for the synthesis of C–N bonds usually originates from NH 3 − or metal nitride ions (MNH x + , x = 0–2) ,, in gas-phase reactions, where the nitrogen is in the atomic (N) rather than the molecular (N 2 ) state. For instance, the reaction of metal-carbene complexes (MCH 2 + ) with NH 3 is one of the major strategies reported in the literature .…”

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

“…As shown in Figure 3 cations is one important factor to promote the reaction. The bond dissociation energy of Sc + −O is 7.14 eV, and formation of ScO + drives the ScNH + + H 2 O reaction as well as the ScNH + + CO 2 → ScO + + HNCO reaction, which is reported in ref 59. DFT-calculated and experimental bond dissociation energies can be found in previous work.…”

“…Figure is a plot of the PES for the reaction of ScNH + with H 2 O. The structure of ScNH + has been calculated using several different functionals, and the lowest energy is a singlet state with a linear structure. As shown in Figure , the encounter complex I1 is initially formed from the reactants ScNH + and H 2 O with an energy gain of 1.69 eV.…”

“…DFT-calculated and experimental bond dissociation energies can be found in previous work. 59 Water activation mediated by gas-phase transition metal oxide clusters has been extensively studied, 28−34 . 62,63 Moreover, a novel channel is found, in which H 2 O is dehydrogenated by the reactive ScNH + , with the formation of NH 3 .…”

“…56 The dispersion effect, 57 which can be explicitly estimated from the DFT-D3 correction of the complexes, 58 is included in our systems. According to our previous work, 59 the level of theory is quantitatively adequate for elucidating the system studied.…”