The nature of [N-Cl-N]+ and [N-F-N]+ halogen bonds in solution
Artikel i vetenskaplig tidskrift, 2014

Halonium ions are synthetically useful, transient species that may be stabilized by attachment to two electron donors. Whereas studies of [C–X–C]+-type ions have greatly contributed to the fundamental understanding of chemical bonding and reaction mechanisms, investigations of the corresponding [N–X–N]+ halogen bond complexes are only at an early stage. Herein we present solution NMR spectroscopic and theoretical evidence for the nature of [N–Cl–N]+ and [N–F–N]+ complexes, and we discuss their geometries and stabilities in comparison to their iodine and bromine-centered analogues as well as the corresponding three-center [N–H–N]+ hydrogen bond. We show the chlorine-centered halogen bond to be weaker but yet to resemble the symmetric geometry of the three-center bond of heavier halogens. In contrast, the [N–F–N]+ bond is demonstrated to prefer asymmetric geometry analogous to the [N–H–N]+ hydrogen bond. However, the [N–F–N]+ system has a high energy barrier for interconversion, and due to entropy loss, its formation is slightly endothermic.

symmetry

solution

structure

halogen bond

NMR

Författare

Alavi Karim

Göteborgs universitet

Marcus Reitti

Göteborgs universitet

Anna-Carin Carlsson

Göteborgs universitet

Jürgen Gräfenstein

Göteborgs universitet

Mate Erdelyi

Göteborgs universitet

Chemical Science

2041-6520 (ISSN) 2041-6539 (eISSN)

Vol. 5 3226-3233

Ämneskategorier

Analytisk kemi

Organisk kemi

DOI

10.1039/C4SC01175A