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

The complexes of TrR3 (Tr = B and AI; R = H, F, Cl, and Br) with three N-bases (NH3, CH2NH, and HCN) and three O-bases (CH3OH, H2CO, 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 TrR3. 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 BH3 complex.