Terminal end‐on coordination of dinitrogen versus isoelectronic CO : A comparison using the charge displacement analysis

The metal dinitrogen bonding in a wide series of terminal end‐on dinitrogen complexes is investigated with the charge displacement analysis based on natural orbitals of chemical valence (CD‐NOCV). The effect of the σ donation and π backdonation on the NN bond are discussed and compared with the observations for a series of carbonyl complexes, published in 2016 by Tarantelli et al. The σ donation is relative invariant over the series of dinitrogen complexes and has no significant effect on the NN bond strength, whereas the π backdonation causes a considerable elongation of the NN bond. Some uncommon examples of weakly bound dinitrogen with blue‐shifted stretching frequency compared to free N 2 ( ν  = 2330 cm −1 ) are known. The dinitrogen bonding in these complexes is simulated with a point charge. Apparently, electrostatics account for the shortened N─N bond in these systems.