Comparison of sigma-/pi-Hole Tetrel Bonds between TH3F/F2TO and H2CX (X=O, S, Se)

摘要

Several sigma-hole and pi-hole tetrel-bonded complexes with a base H2CX (X=O, S, Se) have been studied, in which TH3F (T=C-Pb) and F2TO (T=C and Si) act as the sigma-hole and pi-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 TH3F, whereas two minima tetrel-bonded complexes for some F2TO. H2CX is favorable to engage in the pi-hole complex with F2TO relative to TH3F in most cases, and this preference further expands for the Si complex. Particularly, the double pi-hole complex between F2SiO and H2CX (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 sigma-hole interaction and the pi-hole interaction are weaker for the heavier chalcogen atom, while the pi-hole interaction involving F2TO (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.