Synthesis and Structures of Novel Molecular Ionic Compounds Based on Encapsulation of Anions and Cations

El Aziz, Youssef; Taylor, Peter G.; Bassindale, Alan R.; Coles, Simon J. and Pitak, Mateusz B. (2016). Synthesis and Structures of Novel Molecular Ionic Compounds Based on Encapsulation of Anions and Cations. Organometallics, 35(24) pp. 4004–4013.

DOI: https://doi.org/10.1021/acs.organomet.6b00565

Abstract

The novel coordinate compounds T₈[(CH₂)_n-EWG]₈F⁻-18-crown-6-M⁺ were prepared by reaction of EWG-(CH₂)_n-Si(OEt)₃ (where n = 1−3 and the electron-withdrawing group, EWG, contains an Si−C(sp³) bond) with an 18-crown-6-M⁺F⁻ complex (where M⁺ is K⁺, Cs⁺, and Rb⁺) in the presence of a limited amount of water. The EWG facilitates the formation and encapsulation of the fluoride anion in a silsesquioxane cage. The reaction takes place by complexing an alkali metal in the crown ether, catalyzing silsesquioxane cage formation, and concomitant encapsulation of a fluoride ion within the final T₈ cage. The reaction is simple and takes place in a single step with excellent yields of 81−95%. These novel materials have been studied by ¹⁹F and ²⁹Si NMR spectroscopy and X-ray crystallography as well as by MALDI-TOF and ESI mass spectrometry. The T₈[(CH₂)_n-EWG]₈F⁻-18-crown-6-M⁺ compounds can be also synthesized by a facile reaction of 18-crown-6-M⁺F⁻ with the corresponding T₈[(CH₂)_n-EWG]₈ cage in nearly quantitative yield. Surprisingly, the single-crystal X-ray diffraction analysis has revealed the presence of 1D and 3D polymeric complexes of T₈[(CH₂)_n-EWG]₈F⁻-18-crown-6-M⁺. To the best of our knowledge, this represents the first dual-encapsulation host−octasilsesquioxane system. The results from thermostability experiments monitored by ¹⁹F NMR and ¹H NMR and DSC suggest that compound T₈[CH₂CH₂(CF₂)₃CF₃]₈F⁻-18-crown-6-K⁺ is a potential ionic liquid (IL).

Viewing alternatives

Metrics

Item Actions

Export

You can export this page using these formats Digital Object Identifier - DOI