Single‐Crystal X‐ray Diffraction and Solution Studies of Anion–π Interactions in N‐(Pentafluorobenzyl)pyridinium Salts

Abstract

A solid‐state structural study on anion–π interaction in various N‐(pentafluorobenzyl)pyridinium salts accompanied by NMR spectroscopic investigations is presented. The crystal structures of 1a–1d reveal different kinds of contacts with anions, including anion–π interactions. In particular, the solid‐state structure of 1b‐I3 shows distinct evidence of anion–π interactions. Attempts to study anion–π interactions in solution were not successful, but their presence in solution could not be ruled out.

Anion‐Binding Catalysis by Electron‐Deficient Pyridinium Cations

“…The results summarized in Table 1 allow the following conclusions: 1) Most importantly, the triply substituted pyridinium tetrafluoroborates 6 d-g·BPh 4 indeed act as efficient catalysts for the alkylation of 1-chloroisochroman (1 a) and also of the acyclic chlorobenzyl ether 1 b, with all four of the silyl ketene acetals (2 a-d) tested (Table 1, entries 2-6, [8][9][10][11][13][14][15]. For the more reactive electrophile 1 a in combination with the silyl ketene acetal 2 a, catalyst loading as low as 2 mol % is sufficient to achieve full conversion within a few hours at À78 8C (entry 3).…”

Anion−π Interactions with Fluoroarenes

“…Investigated anion-exchange equilibrium for tert-butylpentafluorobenzylpyridinium salts 34a−e and pyridinium salts studied in the crystal 128. bromide) in between two electron-deficient arene moieties 146.…”

Construction of Supramolecular Assemblies Based on Anion–π Interactions

“…The same group has also used N-(pentafluorobenzyl)pyri dinium salts to investigate the anion size dependence in solid-state structures exhibiting anion-π interactions [114]. In this example, both C 6 F 5 and pyridinium moieties are involved in the anion-π contacts (Fig.…”

“…They have established new elements of stabilization utilizing the phosphonium group, enabling the isolation of the first NDI-based radical FIgURE 11.16 X-ray crystal structures of XIVJIX, XIVJET, and XIVJOD[114]. The CSD reference codes are indicated.…”