Effect of carbon hybridization in C-F bond as an electron donor in triel bonds.

The ability of the F atom of HC≡CF, HC=CHF and HCCHF to serve as an electron donor to the triel (Tr) atom of TrR in the context of a triel bond is assessed by ab initio calculations. The triel bond formed by C-F is strongest, as high as 30 kcal/mol, followed by C-F, and then by C-F whose triel bonds can be as small as 1 kcal/mol. The noncovalent bond strength diminishes in the order Tr = Al > Ga > B, consistent with the intensity of the π-hole above the Tr atom in the monomer.

Violation of Electrostatic Rules: Shifting the Balance between Pnicogen Bonds and Lone Pair-π Interactions Tuned by Substituents.

Complexes were formed by pairing ZCl (Z = P, As, or Sb) with CR (R = H, F, or CN). The first interaction present is a pnicogen bond between the Z atom and the C═C π-bond. This bond weakens as the H atoms of ethylene are replaced by electron-withdrawing F and CN, and the potential above the alkene switches from negative to positive.