Enhancement of tetrel bond involving tetrazole-TtR 3 (Tt = C, Si; R = H, F). Promotion of SiR 3 transfer by a triel bond.

When attached to a tetrazole, a TtR 3 group (Tt = C, Si; R = H, F) engages in a Tt⋯N tetrel bond (TtB) with the Lewis base NCM (M = Li, Na). MP2/aug-cc-pVTZ calculations find that the Si⋯N TtB is rather strong, more than 20 kcal mol -1 for SiH 3 , and between 46 and 53 kcal mol -1 for SiF 3 . The C⋯N TtBs are relatively weaker, less than 8 kcal mol -1 . All of these bonds are intensified when a BH 3 or BF 3 molecule forms a triel bond to a N atom of the tetrazole ring, particularly for the C⋯N TtB, up to 11 kcal mol -1 . In these triads, the SiR 3 group displaces far enough along the line toward the base that it may be thought of as half transferred.