Tetrel bond involving -CH3 group in HnXCH3 (X = F, Cl, and Br, n=0; X = O, S, and Se, n=1; X = N, P, and As, n=2). Cooperativity with triel bond and beryllium bond

The tetrel bond formed between the sigma-hole on the C atom of HnXCH3 (X = F, Cl, and Br, n = 0; X = O, S, and Se, n = 1; X = N, P, and As, n = 2) and the N atom of NCM (M = Li and Na) was studied by ab initio calculations at the MP2/aug-cc-pVTZ level. The molecules involving nitrogen or oxygen group substituents engage in a weaker tetrel bond with interaction energies in the range of 5-12 kJ/mol. In contrast, a stronger tetrel bond is formed when the X atom of HnXCH3 is a halogen, with interaction energies in the range of 16-18 kJ/mol. The tetrel bond is further enhanced by the addition of the electron-deficient molecule BeH2 or BH3 to the X atom of HnXCH3 and the interaction energy can be increased to 38 kJ/mol. Moreover, the enhancing effect of beryllium bond on the tetrel bond is greater than that from the triel bond.