Counterion influence on the N–I–N halogen bond

Abstract

Counterions influence three-center halogen bonds differently than coordination bonds of transition metals.

Solvent Effects on Nitrogen Chemical Shifts

“…28) determined for dichloromethane-d 2 solution are shown in Table 19. In agreement with diffusion NMR data [146] all counterions were tightly coordinated to Ag(I). The magnitude of jΔ 15N coord j suggests increasing coordination strength in the order SbF 6 À < PF 6 À < BF 4 À < ClO 4 À < OTf À < NO 3 À < OTs À < CF 3 CO 2 À (218-225).…”

“…The counterion of the [N-I-N] + complexes (236-243) does not directly interact with the central halogen, in contrast to numerous corresponding transition metal complexes (Table 19), as indicated by the comparable jΔ 15N coord j obtained for the dichloromethane-d 2 solutions (Table 21) [146]. In an apolar solvent, all counterions are strongly attached to the [N-X-N] + system, yet do not directly coordinate as it was confirmed by DFT and X-ray crystallographic studies.…”

Halogen-Bonded Co-Crystals of Aromatic N-oxides: Polydentate Acceptors for Halogen and Hydrogen Bonds

“…Halogen bonds are frequently studied using nitrogen compounds, which typically display monovalent N···X (X = I, Br) interactions and are well understood as crystal engineering tools for self-assembly processes. Their precedence from discrete structures to increased dimensionality through the controlled reactivity of substrates is well-reported [10][11][12][13]. In a solid-state XB complex, R−X···B−Z, where X is the donor and B is the acceptor atom, the ratio of the short distance between X and B atoms (d X-B ) to sum of the Van der Waals radii of X and B atoms (d vdW ) is defined as the normalized strength parameter, R XB = d X-B /d vdW [1].…”

Characterization of Halogen Bonded Adducts in Solution by Advanced NMR Techniques

“…In the author's opinion, since some of the employed anions contains fluorine nuclei, a 19 F, 1 H HOESY experiment between the anion and the cation (see above) could have further clarified this point. The [N-X-N] + system remains symmetrical, also varying the nature of the anion [104]. A notable exception has been found when X = F, for which the asymmetric conformation is preferred [105].…”