Comparison for σ-hole and π-hole tetrel-bonded complexes involving F2C[dbnd]CFTF3 (T[dbnd]C, Si, and Ge): Substitution, hybridization, and solvation effects

Abstract

An ab initio calculation has been performed for the complexes of F2CCFTF3 (TC, Si, and Ge) with three Lewis bases including H2CO, H2O, and NH3. Most complexes are stabilized by tetrel bonds together with weak hydrogen bonds. The Lewis bases can be introduced to the σ-hole and π-hole of F2CCFTF3, but the σ-hole bonded complexes are preferential for F2CCFTF3 (TSi and Ge), while the π-hole bonded complexes are favorable for F2CCFCF3. Hybridization of the carbon atom adjoined with the SiF3 group strengthens the σ-hole tetrel bond in the order sp3 < sp2 < sp, similar to hydrogen and halogen bonds. The strength of σ-hole tetrel bond is also dependent on the number, position, and conformation of substituents. In addition, solvents have a prominent enhancing effect on the strength of σ-hole tetrel bond with about 0.1 Å shortening of the Si⋯N distance in water.