Comparison of pnicogen and tetrel bonds in complexes containing CX 2 carbenes (X = F, Cl, Br, OH, OMe, NH 2 , and NMe 2 )

The similarities and differences of pnicogen and tetrel bonds formed by CX 2 carbenes (X = F, Cl, Br, OH, OMe, NH 2 , and NMe 2 ) with σ-holes of H 3 AsO and H 3 SiCN were investigated by carrying out ab initio calculations in association with topological analysis of electron density and energy decomposition analysis. The strength of the σ-hole interactions was found to be essentially related to the nature of the group IV/V atom and the substituent of the carbene. The interaction energies of the tetrel-bonded complexes were calculated to be more negative than those of the corresponding pnicogen-bonded complexes except for H 3 SiCN⋯CF 2 . In the formation of the complexes, the geometries of the H 3 AsO⋯CX 2 systems did not change much, while greater deformations occurred for the H 3 SiCN⋯CX 2 systems. Our analyses also show a large contribution made by the deformation energy to the tetrel bond and all of the pnicogen bonds displaying the closed shell characteristics of the weak interactions, as well as most of the tetrel bonds having partially covalent character, consistent with the remarkable induced dipole interaction between the two monomers. For the tetrel-bonded complexes, the polarization energies were found to exhibit a polynomial dependence on the change of the dihedral angle of the SiH 3 fragment and the increase of integral charge in the Si⋯C internuclear region.