Unusual substituent effects in the Tr···Te triel bond

The triel bond between the π‐hole on the triel atom of TrR 3 (Tr = B, Al, Ga; R = H, F, Cl, Br) and a lone pair on the Te atom of H 2 Te is examined using ab initio methods. For Tr = B, the triel bond is weakened as the R substituent becomes more electronegative, while the opposite pattern is noted for Al and Ga. The weakest triel bond of all occurs in H 2 Te‐BF 3 (2.9 kcal/mol) but is much stronger for all the other complexes (>11 kcal/mol). The placement of electron‐releasing OH, NH 2 , and CH 3 R′ substituents on the R′ 2 Te base strengthens the triel bond, whereas the opposite occurs for the electron‐withdrawing CN. Despite its high electronegativity, the F substituent causes a strengthening of the interaction, which is due in large part to the formation of secondary chalcogen bonds that involve the σ‐holes on Te in F 2 Te. However, the F atom on TrF 3 is unable to act as an electron donor in these chalcogen bonds, leading to weakened F 2 Te··TrF 3 interactions.