Modulating the strength of tetrel bonding through beryllium bonding

Quantum chemical calculations were performed to investigate the stability of the ternary complexes BeH···XMH···NH (X = F, Cl, and Br; M = C, Si, and Ge) and the corresponding binary complexes at the atomic level. Our results reveal that the stability of the XMH···BeH complexes is mainly due to both a strong beryllium bond and a weak tetrel–hydride interaction, while the XMH···NH complexes are stabilized by a tetrel bond. The beryllium bond with a halogen atom as the electron donor has many features in common with a beryllium bond with an O or N atom as the electron donor, although they do exhibit some different characteristics. The stability of the XMH···NH complex is dominated by the electrostatic interaction, while the orbital interaction also makes an important contribution. Interestingly, as the identities of the X and M atoms are varied, the strength of the tetrel bond fluctuates in an irregular manner, which can explained by changes in electrostatic potentials and orbital interactions. In the ternary systems, both the beryllium bond and the tetrel bond are enhanced, which is mainly ascribed to increased electrostatic potentials on the corresponding atoms and charge transfer. In particular, when compared to the strengths of the tetrel and beryllium bonds in the binary systems, in the ternary systems the tetrel bond is enhanced to a greater degree than the beryllium bond. [Figure not available: see fulltext.]