Issue 30, 2020

Symmetry of three-center, four-electron bonds


Three-center, four-electron bonds provide unusually strong interactions; however, their nature remains ununderstood. Investigations of the strength, symmetry and the covalent versus electrostatic character of three-center hydrogen bonds have vastly contributed to the understanding of chemical bonding, whereas the assessments of the analogous three-center halogen, chalcogen, tetrel and metallic [small sigma, Greek, circumflex]-type long bonding are still lagging behind. Herein, we disclose the X-ray crystallographic, NMR spectroscopic and computational investigation of three-center, four-electron [D–X–D]+ bonding for a variety of cations (X+ = H+, Li+, Na+, F+, Cl+, Br+, I+, Ag+ and Au+) using a benchmark bidentate model system. Formation of a three-center bond, [D–X–D]+ is accompanied by an at least 30% shortening of the D–X bonds. We introduce a numerical index that correlates symmetry to the ionic size and the electron affinity of the central cation, X+. Providing an improved understanding of the fundamental factors determining bond symmetry on a comprehensive level is expected to facilitate future developments and applications of secondary bonding and hypervalent chemistry.

Graphical abstract: Symmetry of three-center, four-electron bonds

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Article information

Article type
Edge Article
11 Apr 2020
19 Jun 2020
First published
30 Jun 2020
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY license

Chem. Sci., 2020,11, 7979-7990

Symmetry of three-center, four-electron bonds

A. C. Reiersølmoen, S. Battaglia, S. Øien-Ødegaard, A. K. Gupta, A. Fiksdahl, R. Lindh and M. Erdélyi, Chem. Sci., 2020, 11, 7979 DOI: 10.1039/D0SC02076A

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