C∙∙∙O and Si∙∙∙O Tetrel Bonds: Substituent Effects and Transfer of the SiF 3 Group.

The tetrel bond (TB) between 1,2-benzisothiazol-3-one-2-TF 3 -1,1-dioxide (T = C, Si) and the O atom of pyridine-1-oxide (PO) and its derivatives (PO-X, X = H, NO 2 , CN, F, CH 3 , OH, OCH 3 , NH 2 , and Li) is examined by quantum chemical means. The Si∙∙∙O TB is quite strong, with interaction energies approaching a maximum of nearly 70 kcal/mol, while the C∙∙∙O TB is an order of magnitude weaker, with interaction energies between 2.0 and 2.6 kcal/mol. An electron-withdrawing substituent on the Lewis base weakens this TB, while an electron-donating group has the opposite effect. The SiF 3 group transfers roughly halfway between the N of the acid and the O of the base without the aid of cooperative effects from a third entity.