Enhancement of tetrel bond involving tetrazole-TtR3 (Tt = C, Si; R = H, F). Promotion of SiR3 transfer by a triel bond.

When attached to a tetrazole, a TtR3 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 SiH3, and between 46 and 53 kcal mol-1 for SiF3. The C⋯N TtBs are relatively weaker, less than 8 kcal mol-1. All of these bonds are intensified when a BH3 or BF3 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 SiR3 group displaces far enough along the line toward the base that it may be thought of as half transferred.