Chemical pressure-chemical knowledge: Squeezing bonds and lone pairs within the valence shell electron pair repulsion model
| Autor: | Mercedes Taravillo, J. M. Recio, Miguel A. Salvadó, Valentín G. Baonza, Álvaro Lobato, Hussien H. Osman |
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| Přispěvatelé: | Ministerio de Ciencia e Innovación (España) |
| Rok vydání: | 2019 |
| Předmět: |
Physics
VSEPR theory General Physics and Astronomy 02 engineering and technology 010402 general chemistry 021001 nanoscience & nanotechnology 01 natural sciences Potential energy 0104 chemical sciences Electronegativity Molecular geometry Chemical bond Chemical physics Atom Molecule Physical and Theoretical Chemistry 0210 nano-technology Lone pair |
| Zdroj: | Digital.CSIC. Repositorio Institucional del CSIC instname Scopus RUO. Repositorio Institucional de la Universidad de Oviedo |
| Popis: | The valence shell electron pair repulsion (VSEPR) model is a demanding testbed for modern chemical bonding formalisms. The challenge consists in providing reliable quantum mechanical interpretations of how chemical concepts such as bonds, lone pairs, electronegativity, or hypervalence influence (or modulate) molecular geometries. Several schemes have been developed thus far to visualize and characterize these effects; however, to the best of our knowledge, no scheme has yet incorporated the analysis of the premises derived from the ligand close-packing (LCP) extension of the VSEPR model. Within the LCP framework, the activity of the lone pairs of the central atom and ligand-ligand repulsions constitute the two key features necessary to explain certain controversial molecular geometries that do not conform to the VSEPR rules. Considering the dynamical picture obtained when electron local forces at different nuclear configurations are evaluated from first-principles calculations, we investigate the chemical pressure distributions in a variety of molecular systems, namely, electron-deficient molecules (BeH, BH, BF), several AX series (A: N, P, As; X: H, F, Cl), SO, ethylene, SF, ClF, XeF, and nonequilibrium configurations of water and ammonia. Our chemical pressure maps clearly reveal space regions that are totally consistent with the molecular and electronic geometries predicted by VSEPR and provide a quantitative correlation between the lone pair activity of the central atom and electronegativity of ligands, which are in agreement with the LCP model. Moreover, the analysis of the kinetic and potential energy contributions to the chemical pressure allows us to provide simple explanations on the connection between ligand electronegativity and electrophilic/nucleophilic character of the molecules, with interesting implications in their potential reactivity. NH, NF, SO, BF, and the inversion barrier of AX molecules are selected to illustrate our findings. This work was supported by MICINN and MINECO through the following projects: CTQ2015-67755-C2-R and MAT2015-71070- REDC. Funding was also provided by the Grant UCM-GR17- 910481 from the Universidad Complutense de Madrid. FICYTPrincipado de Asturias (Project FC-GRUPIN-IDI/2018/000177) is gratefully acknowledged. A. Lobato acknowledges financial support from FPU grant no. FPU13/05731. Finally, we would like to thank J. Andres for engaging discussions regarding the applications of the CP formalism to the VSEPR theory. |
| Databáze: | OpenAIRE |
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