Comparison of σ-/π-Hole Tetrel Bonds between TH₃ F/F₂ TO and H₂ CX (X=O, S, Se)

Several σ-hole and π-hole tetrel-bonded complexes with a base H₂ CX (X=O, S, Se) have been studied, in which TH₃ F (T=C-Pb) and F₂ TO (T=C and Si) act as the σ-hole and π-hole donors, respectively. Generally, these complexes are combined with a primary tetrel bond and a weak H-bond. Only one minimum tetrel-bonded structure is found for TH₃ F, whereas two minima tetrel-bonded complexes for some F₂ TO. H₂ CX is favorable to engage in the π-hole complex with F₂ TO relative to TH₃ F in most cases, and this preference further expands for the Si complex. Particularly, the double π-hole complex between F₂ SiO and H₂ CX (X=S and Se) has an interaction energy exceeding 500 kJ/mol, corresponding to a covalent-bonded complex with the huge orbital interaction and polarization energy. Both the σ-hole interaction and the π-hole interaction are weaker for the heavier chalcogen atom, while the π-hole interaction involving F₂ TO (T=Ge, Sn, and Pb) has an opposite change. Both types of interactions are electrostatic in nature although comparable contributions from dispersion and polarization are respectively important for the weaker and stronger interactions.