Substituent Effects on the [N–I–N]+ Halogen Bond
Artikel i vetenskaplig tidskrift, 2016

We have investigated the influence of electron density on the three-center [N–I–N]+ halogen bond. A series of [bis(pyridine)iodine]+ and [1,2-bis((pyridine-2-ylethynyl)benzene)iodine]+ BF4– complexes substituted with electron withdrawing and donating functionalities in the para-position of their pyridine nitrogen were synthesized and studied by spectroscopic and computational methods. The systematic change of electron density of the pyridine nitrogens upon alteration of the para-substituent (NO2, CF3, H, F, Me, OMe, NMe2) was confirmed by 15N NMR and by computation of the natural atomic population and the π electron population of the nitrogen atoms. Formation of the [N–I–N]+ halogen bond resulted in >100 ppm 15N NMR coordination shifts. Substituent effects on the 15N NMR chemical shift are governed by the π population rather than the total electron population at the nitrogens. Isotopic perturbation of equilibrium NMR studies along with computation on the DFT level indicate that all studied systems possess static, symmetric [N–I–N]+ halogen bonds, independent of their electron density. This was further confirmed by single crystal X-ray diffraction data of 4-substituted [bis(pyridine)iodine]+ complexes. An increased electron density of the halogen bond acceptor stabilizes the [N···I···N]+ bond, whereas electron deficiency reduces the stability of the complexes, as demonstrated by UV-kinetics and computation. In contrast, the N–I bond length is virtually unaffected by changes of the electron density. The understanding of electronic effects on the [N–X–N]+ halogen bond is expected to provide a useful handle for the modulation of the reactivity of [bis(pyridine)halogen]+-type synthetic reagents.

Författare

Anna-Carin Carlsson

Göteborgs universitet

Krenare Mehmeti

Göteborgs universitet

Martin Uhrbom

Göteborgs universitet

Alavi Karim

Göteborgs universitet

Michele Bedin

Göteborgs universitet

Rakesh Puttreddy

Roland Kleinmaier

Göteborgs universitet

Alexei A Nevorov

Bijan Nekouesihahraki

Göteborgs universitet

Jürgen Gräfenstein

Göteborgs universitet

Kari Rissanen

Mate Erdelyi

Göteborgs universitet

Journal of the American Chemical Society

0002-7863 (ISSN) 1520-5126 (eISSN)

Vol. 138 31 9853-9863

Ämneskategorier

Kemi

DOI

10.1021/jacs.6b03842