Structural Versatility of Anion−π Interactions in Halide Salts with Pentafluorophenyl Substituted Cations

Abstract

A series of pentafluorophenyl substituted ammonium, iminium, amidinium, and phosphonium halides are presented which show extensive anion-pi interactions. Hereby, the well-known anion-donor-pi-acceptor as well as "eta6" anion-pi-complex type interactions are observed. The latter is supported by fixation of the anion on top of the aromatic system through hydrogen bonding. This arrangement was investigated by theoretical methods showing a highly attractive anion-pi interaction. In addition an eta2-type coordination of the anions to only two C-atoms of the electron-deficient ring system is described.

Anion−π Interactions with Fluoroarenes

“…In 2008 this series was extended by a crystallographic study performed by us. 96 X-ray structures reveal two additional binding motifs for spatially different interactions of anions and electron-deficient π-systems, viz. interaction with two (G) or three carbon atoms (H), respectively ( Figure 8).…”

Versatile Anion–π Interactions between Halides and a Conformationally Rigid Bis(tetraoxacalix[2]arene[2]triazine) Cage and Their Directing Effect on Molecular Assembly

“…A number of experimental studies [4] have demonstrated interactions between anions and p systems; however, experimental evidence to support "pure" anion-p interactions with charge-neutral arenes is very rare. [3,5] Indeed, a recent report indicated that the noncovalent anion-p interaction contributes less significantly to the formation of chloride-p-C 6 F n H 6Àn complex.…”

“…An isothermal titration calorimetry (ITC) [8] study revealed that, in acetonitrile, the cage molecule formed 1:1 complexes with fluoride, chloride, and bromide, with association constant being 361, 146, and 95 m À1 , respectively. Scheme 1 illustrates the synthesis of cage molecule, bis(tetraoxacalix [2]arene [2]triazine) (4). The reaction of phloroglucinol 1 with an excess amount of cyanuric chloride 2 in the presence of diisopropylethylamine (DIPEA) at 0 8C gave intermediate 3 in 75 % yield.…”

“…The interaction of host molecule 4 with chloride and bromide in solution was also evidenced by the observation of [4&Cl] À and [4&Br] À ion peaks in ESI mass spectra (see Figure S17 and S18 Supporting Information) when 4 was treated with tetrabutylammonium chloride and bromide, respectively. Additionally, ion peaks corresponding to [4&Bu 4 NX&X] À and [4&2X] À (X = Cl and Br) were also observed, indicating the formation of multiple component complexes between host and guest under mass spectrometry conditions. In summary, we have shown that bis(tetraoxacalix[2]-A C H T U N G T R E N N U N G arene [2]triazine) 4, a conformationally rigid cage molecule with three V-shaped electron-deficient clefts, was able to interact with halides.…”

Studies on structural and magnetic properties of hydrochloride crystals based on 2-(imidazo[1,2–a]pyridin-2-yl)-2-oxoacetic acid radical

“…1a. The observed Cl À -p interactions in 1 should be described as a Z 1 -type interaction [17]. Different from 1, crystal 2 contains another guest methanol molecule apart from one guest water molecule.…”