Side-On Bound Beryllium Dinitrogen Complex: A Precursor for Complete Conversion of Dinitrogen to Ammonia Mediated by N-Heterocyclic Carbene.

The complete conversion of dinitrogen to ammonia mediated by a side-on N₂-bound carbene-beryllium complex, [NHC-Be(η²-N₂)] has been studied considering both the symmetric and unsymmetric pathways. N-heterocyclic carbenes complexed with Be(η²-N₂) moieties were considered substrates in our study. We found that two mechanistic pathways were possible for the reduction of dinitrogen to form ammonia. Our calculations revealed that the symmetric pathway is more favorable compared to the unsymmetric one. The interconversion of the complex from the symmetric product to the unsymmetric one involves a large activation energy barrier for the proton transfer pathway. Both of these pathways were associated with high exergonicity, and the N-N bond is observed to be elongated, which indicates that the NHC-Be(η²-N₂) complex is a promising candidate for dinitrogen activation and subsequent reduction, resulting in the formation of ammonia. The bonding scenario of the NHC-Be(η²-N₂) complex can be explained well by the famous Dewar-Chatt-Duncanson (DCD) model. Our calculations reveal that the symmetric pathway is found to be more suitable due to more negative values of change in Gibbs free energy. Solvent phase calculations have identified the viability of the NHC-Be(η²-N₂) complex, indicating that the complex is sustainable in low-polar organic solvents, such as toluene and diethyl ether.