Influence of N-Base and O-Base Hybridization on Triel Bonds

The complexes of TrR 3 (Tr = B and Al; R = H, F, Cl, and Br) with three N-bases (NH 3 , CH 2 NH, and HCN) and three O-bases (CH 3 OH, H 2 CO, and CO) are utilized to explore the hybridization effect of N and O atoms on the strength, properties, and nature of the triel bond. The sp-hybridized O and N atoms form the weakest triel bond, followed by the sp 2 -hybridized O atom or the sp 3 -hybridized N atom, and the sp 3 -hybridized O atom or the sp 2 -hybridized N atom engages in the strongest triel bond. The hybridization effect is also related to the substituent of TrR 3 . Most complexes are dominated by electrostatic, with increasing polarization contribution from sp to sp 2 to sp 3 . Although the CO oxygen engages in a weaker triel bond, its carbon atom is a better electron donor and the interaction energy even amounts to -37 kcal/mol in the BH 3 complex.