Noncovalent bond between tetrel π-hole and hydride

Abstract

The π-hole above the plane of the X₂T′Y molecule (T′ = Si, Ge, Sn; X = F, Cl, H; Y = O, S) was allowed to interact with the TH hydride of TH(CH₃)₃ (T = Si, Ge, Sn). The resulting TH⋯T′ tetrel bond is quite strong, with interaction energies exceeding 30 kcal mol⁻¹. F₂T′O engages in the strongest such bonds, as compared to F₂T′S, Cl₂T′O, or Cl₂T′S. The bond weakens as T′ grows larger as in Si > Ge > Sn, despite the opposite trend in the depth of the π-hole. The reverse pattern of stronger tetrel bond with larger T is observed for the Lewis base TH(CH₃)₃, even though the minimum in the electrostatic potential around the H is nearly independent of T. The TH⋯T′ arrangement is nonlinear which can be understood on the basis of the positions of the extrema in the molecular electrostatic potentials of the monomers. The tetrel bond is weakened when H₂O forms an O⋯T′ tetrel bond with the second π-hole of F₂T′O, and strengthened if H₂O participates in an OH⋯O H-bond.