Publication: Estimations of Fe<sup>0/-1</sup>-N<inf>2</inf>interaction energies of iron(0)-dicarbene and its reduced analogue by EDA-NOCV analyses: Crucial steps in dinitrogen activation under mild conditions
Date
26-01-2022
Authors
Kartik Chandra Mondal
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Abstract
Metal complexes containing low valence iron atoms are often experimentally observed to bind with the dinitrogen (N2) molecule. This phenomenon has attracted the attention of industrialists, chemists and bio-chemists since these N2-bonded iron complexes can produce ammonia under suitable chemical or electrochemical conditions. The higher binding affinity of the Fe-atom towards N2 is a bit 'mysterious' compared to that of the other first row transition metal atoms. Fine powders of α-Fe0 are even part of industrial ammonia production (Haber-Bosch process) which operates at high temperature and high pressure. Herein, we report the EDA-NOCV analyses of the previously reported dinitrogen-bonded neutral molecular complex (cAACR)2Fe0-N2 (1) and mono-anionic complex (cAACR)2Fe-1-N2 (2) to give deeper insight of the Fe-N2 interacting orbitals and corresponding pairwise intrinsic interaction energies (cAACR = cyclic alkyl(amino) carbene; R = Dipp or Me). The Fe0 atom of 1 prefers to accept electron densities from N2via σ-donation while the comparatively electron rich Fe-1 centre of 2 donates electron densities to N2via π-backdonation. However, major stability due to the formation of an Fe-N2 bond arises due to Fe → N2 π-backdonation in both 1 and 2. The cAACR ligands act as a charge reservoir around the Fe centre. The electron densities drift away from cAAC ligands during the binding of N2 molecules mostly via π-backdonation. EDA-NOCV analysis suggests that N2 is a stronger π-acceptor rather than a σ-donor. This journal is