EDA‐NOCV analysis of carbene‐borylene bonded dinitrogen complexes for deeper bonding insight: A fair comparison with a metal‐dinitrogen system

Abstract

Binding of dinitrogen (N 2 ) to a transition metal center (M) and followed by its activation under milder conditions is no longer impossible; rather, it is routinely studied in laboratories by transition metal complexes. In contrast, binding of N 2 by main group elements has been a challenge for decades, until very recently, an exotic cAAC-borylene (cAAC = cyclic alkyl(amino) carbene) species showed similar binding affinity to kinetically inert and non-polar dinitrogen (N 2 ) gas under ambient conditions. Since then, N 2 binding by short lived borylene species has made a captivating news in different journals for its unusual features and future prospects. Herein, we carried out different types of DFT calculations, including EDA-NOCV analysis of the relevant cAAC-borondinitrogen complexes and their precursors, to shed light on the deeper insight of the bonding secret (EDA-NOCV = energy decomposition analysis coupled with natural orbital for chemical valence). The hidden bonding aspects have been uncovered and are presented in details. Additionally, similar calculations have been carried out in comparison with a selected stable dinitrogen bridged-diiron(I) complex. Singlet cAAC ligand is known to be an exotic stable species which, combined with the B Ar group, produces an intermediate singlet electron-deficient (cAAC)(B Ar) species possessing a high lying HOMO suitable for overlapping with the high lying π*-orbital of N 2 via effective π-backdonation. The B N 2 interaction energy has been compared with that of the Fe N 2 bond. Our thorough bonding analysis might answer the unasked questions of experimental chemists about how boron compounds could mimic the transition metal of dinitrogen binding and activation, uncovering hidden bonding aspects. Importantly, Pauling repulsion energy also plays a crucial role and decides the binding efficiency in terms of intrinsic interaction energy between the boron-center and the N 2 ligand.

Adsorption properties of M-UiO-66 (M = Zr(iv); Hf(iv) or Ce(iv)) with BDC or PDC linker

“…By means of eqn (5), it is possible to examine these terms individually, explicitly focusing on the processes of electron density outflow and inflow from a specific fragment. 54,59 …”

Revisiting the electronic structure of N2-bound cAAC-borylene at the CASSCF level: a detailed bonding picture of borylene–N2 interaction

“…Since its isolation, complex 1 has been subjected to quite a few theoretical investigations. 5,16,17 Yet, its electronic structure remains elusive to date. In fact, the original work of Braunschweig et al and the DFT-based electronic structure analysis therein can be considered as state-of-the-art in electronic structure understanding, where the authors suggested the π-back-donation being key to the bonding scenario along with σ-donation from N 2 .…”