Role of Fullerene–Nitrogen Complexes of Alkali Metals in C60-Catalyzed Nitrogen Fixation
A. F. Shestakov
Российский журнал физической химии А
https://doi.org/10.1134/S0036024420050209
The key stage of the activation of a nitrogen molecule upon the catalytic reduction of N2 to ammonia in an aqueous medium in the presence of a complex of C60 with γ-cyclodextrin, in the range of potentials of C60 reduction to the dianione, is considered using the PBE density functional. The possible role of the ionic associates (C60)2−(M+)n (n = 1, 2) that inevitably form upon the reduction of C60, due to the presence of a background electrolyte containing alkali metal ions M+, is also studied. It is found that in complexes (C60MN2)−, the bond energy of N2 is 7.0, 5.3, and 4.7 kcal/mol for M = Li, Na, and K, respectively. The M–N distances are 0.2 Å shorter than in cationic complexes (MN2)+, due to electron density transfer from the ligand \({\text{C}}_{{60}}^{{2 - }}\) to the nitrogen molecule. As a result, the N2 molecule is protonated upon the interaction of the neutral associates (C60Li2N2) with a hydroxonium ion. At low energies of activation, the adduct (LiC60LiN2H+ · H2O) transforms to the primary protonated product with a N–C bond and a gain in energy of 10 kcal/mol. Its subsequent reduction to two NH3 molecules encounters no thermodynamic obstacles.
- Institute of Problems of Chemical Physics, Russian Academy of Sciences, 142432, Chernogolovka, Moscow oblast, RussiaA. F. Shestakov
- Department of Physical and Chemical Engineering, Lomonosov Moscow State University, 119991, Moscow, RussiaA. F. Shestakov
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