Nature and Strength of Lewis Acid/Base Interaction in Boron and Nitrogen Trihalides

Daniela Rodrigues Silva, Lucas de Azevedo Santos, Matheus P. Freitas, Célia Fonseca Guerra, Trevor A. Hamlin*

*Corresponding author for this work

Research output: Contribution to JournalArticleAcademicpeer-review


We have quantum chemically investigated the bonding between archetypical Lewis acids and bases. Our state-of-the-art computations on the X3B−NY3 Lewis pairs have revealed the origin behind the systematic increase in B−N bond strength as X and Y are varied from F to Cl, Br, I, H. For H3B−NY3, the bonding trend is driven by the commonly accepted mechanism of donor−acceptor [HOMO(base)−LUMO(acid)] interaction. Interestingly, for X3B−NH3, the bonding mechanism is determined by the energy required to deform the BX3 to the pyramidal geometry it adopts in the adduct. Thus, Lewis acids that can more easily pyramidalize form stronger bonds with Lewis bases. The decrease in the strain energy of pyramidalization on going from BF3 to BI3 is directly caused by the weakening of the B−X bond strength, which stems primarily from the bonding in the plane of the molecule (σ-like) and not in the π system, at variance with the currently accepted mechanism.

Original languageEnglish
Pages (from-to)4043-4054
Number of pages12
JournalChemistry - An Asian Journal
Issue number23
Early online date5 Oct 2020
Publication statusPublished - 1 Dec 2020


  • Activation strain analysis
  • Bond energy
  • Density functional calculations
  • Energy decomposition analysis
  • Lewis acid-base pairs


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