Beryllium atom mediated dinitrogen activation via coupling with carbon monoxide

The reactions of laser-ablated beryllium atoms with dinitrogen and carbon monoxide mixtures form the end-on bonded NNBeCO and side-on bonded (η${}^2$-N${}_2$)BeCO isomers in solid argon, which are predicted by quantum chemical calculations to be almost isoenergetic. The end-on bonded complex has a triplet ground state while the side-on bonded isomer has a singlet electronic ground state. The complexes rearrange to the energetically lowest lying NBeNCO isomer upon visible light excitation, which is characterized to be an isocyanate complex of a nitrene derivative with a triplet electronic ground state. A bonding analysis using a charge- and energy decomposition procedure reveals that the electronic reference state of Be in the NNBeCO isomers has an 2s${}^0$2p${}^2$ excited configuration and that the metal-ligand bonds can be described in terms of N${}_2$→Be←CO σ donation and concomitant N${}_2$←Be→CO π backdonation. The results demonstrate that the activation of N${}_2$ with the N-N bond being completely cleaved can be achieved via coupling with carbon monoxide mediated by a main group atom. (© 2020 The Authors. Published by Wiley-VCH GmbH)