Dinitrogen Binding and Activation: Bonding Analyses of Stable V(III/I)-N-V(III/I) Complexes by the EDA-NOCV Method from the Perspective of Vanadium Nitrogenase.

The FeVco cofactor of nitrogenase (VFeS(CO)C) is an alternative in the molybdenum (Mo)-deficient free soil living azotobacter vinelandii. The rate of N reduction to NH by FeVco is a few times higher than that by FeMoco (MoFeSC) at low temperature. It provides a N source in the form of ammonium ions to the soil. This biochemical NH synthesis is an alternative to the industrial energy-demanding production of NH by the Haber-Bosch process. The role of vanadium has not been clearly understood yet, which has led chemists to come up with several stable V-N complexes which have been isolated and characterized in the laboratory over the past three decades. Herein, we report the EDA-NOCV analyses of dinitrogen-bonded stable complexes V(III/I)-N () to provide deeper insights into the fundamental bonding aspects of V-N bond, showing the interacting orbitals and corresponding pairwise orbital interaction energies (Δ ). The computed intrinsic interaction energy (Δ ) of V-N-V bonds is significantly higher than those of the previously reported Fe-N-Fe bonds. Covalent interaction energy (Δ ) is more than double the electrostatic interaction energy (Δ ) of V-N-V bonds. Δ values of V-N-V bonds are in the range of -172 to -204 kcal/mol. The V → N ← V π-backdonation is four times stronger than V ← N → V σ-donation. V-N bonds are much more covalent in nature than Fe-N bonds.