Electrostatics Explains the Reverse Lewis Acidity of BH3 and Boron Trihalides: Infrared Intensities and a Relative Energy Gradient (REG) Analysis of IQA Energies

Autor(es)

Duarte, Leonardo J. ^[1] ; Richter, Wagner E. ^[2] ; Bruns, Roy E. ^[1] ; Popelier, Paul L. A. ^{[3, 4]}

Afiliação do(s) autor(es)

^[1] Univ Estadual Campinas, Chem Inst, BR-13083861 Campinas, SP - Brazil

^[2] Univ Tecnol Fed Parana, Dept Chem Engn, BR-84017220 Ponta Grossa, Parana - Brazil

^[3] Univ Manchester, Dept Chem, Manchester M13 9PL, Lancs - England

^[4] Manchester Inst Biotechnol MIB, Manchester M1 7DN, Lancs - England

• Tipo de documento: Artigo Científico
• Fonte: Journal of Physical Chemistry A; v. 125, n. 39, p. 8615-8625, OCT 7 2021.
• Citações Web of Science: 0

Resumo

The reaction path for the formation of BX3-NH3 (X = H, F, Cl, Br) complexes was divided into two processes: (i) rehybridization of the acid while adopting a pyramidal geometry, and (ii) the complex formation from the pyramidal geometries of the acid and base. The interacting quantum atom (IQA) method was used to investigate the Lewis acidity trend of these compounds. This topological analysis suggests that the boron-halogen bond exhibits a considerable degree of ionicity. A relative energy gradient (REG) analysis on IQA energies indicates that the acid-base complex formation is highly dependent on electrostatic energy. With increasing halogen electronegativity, a higher degree of ionicity of the B-X is observed, causing an increase in the absolute value of X and B charges. This increases not only the attractive electrostatic energy between the acid and base but also enhances the repulsive energy. The latter is the main factor behind the acidity trend exhibited by trihalides. Changes in geometry are relevant only for complexes where BH3 acts as an acid, where lower steric hindrance facilitates the adoption of the pyramidal geometry observed in the complex. The CCTDP analysis shows that infrared intensities of BX3-NH3 are determined mostly by the atomic charges and not by the charge transfer or polarization. The opposite is observed in covalent analogues. (AU)

• Processo FAPESP: 18/24844-7 - Uso de tensores polares atômicos e parâmetros QCT para treinar um modelo de machine learning e prever constantes de Hammett
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• Processo FAPESP: 17/22741-3 - Uso de multipolos atômicos e desenvolvimento de modelos de machine learning na investigação de estados de transição
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