Triel bonds in RZH···NH: hybridization, solvation, and substitution.

The influence of hybridization, substitution, and solvation on the triel bond has been investigated in the complexes of RZH···NH (Z = B and Al). The magnitude of the π-hole on the triel atom is related to the nature of the Z atom and the hybridization of R. CHBH has the largest π-hole among RBH, while for RAlH the largest π-hole is found in CH≡CAlH. The interaction energy is partly inconsistent with the magnitude of the π-hole on the triel atom and the orbital interaction from the N lone pair of NH into the empty p orbital of the triel atom. The strongest B···N triel bond is found in CH≡CBH···NH, while the weakest Al···N triel bond is in CHAlH···NH. The strength of the triel bond is increased in solvents, and its enhancement is prominent with the increase of solvent polarity. Solvents also change the nature of the Al···N triel bond from an electrostatic interaction to a partially covalent one. The F substituent in the triel donor strengthens the triel bond, depending on the substitution position and number. Graphical Abstract The π-hole triel bonded complexes between RZH2 (Z =B and Al) and NH3 have been investigated. We focused on the effects of hybridization, solvent, and substitution on the strength and nature of π-hole triel bond.