Planar tetracoordinate beryllium compounds with a partially covalent Be-Ng bond.

An analysis of the thermodynamic and kinetic stability and the nature of the chemical bond in hypercoordinated compounds with the formula BeHNg (Ng = He-Rn) through high-level calculations is presented in this work. Thermochemical calculations show that, for the heavier noble gases (Ar-Rn), these systems are thermodynamically stable at room temperature; however, this stability decreases due to a weakening of the Be-H interaction, while the Be-Ng bond strengthens going down the periodic table. These results are complemented by Born Oppenheimer molecular dynamics simulations, in which the increasing tendency to dissociate the Be-H bond is evidenced. The nature of the chemical bonding depends on the analysis performed. On the one hand, the interacting quantum atoms method indicates that the covalent contribution is around 25 to 30%. On the other hand, the electron density topology indicates a covalent nature for compounds with Kr-Rn, while Hirshfeld population analysis in conjunction with Mayer's bond order establishes polar covalent behavior. The geometrical parameters and natural energy decomposition analysis (NEDA) indicate a covalent nature, allowing us to consider that the Be-Ng bond has a partially covalent character.