Syntheses, characterisation and solid-state study of alkali and ammonium BArF salts

Abstract

A new synthetic protocol for synthesising a number of BArF derivatives has been developed. Single crystal X-ray analysis of an array of alkali metal and ammonium salts has allowed the determination of the coordination sphere and/or the map of short contacts of the positively charged atoms. The increasing number of coordination bonds and/or short contacts between the alkali metal cation and the surrounding atoms has been rationalised in terms of the size of the alkali metal centre. It has also been demonstrated that an increase in the number of coordination bonds and/or short contacts translates into longer M–F distances. In the case of the ammonium BArF salts, the N–B distances are shorter than the M–B distances in the alkali metal BArF salts, indicating stronger interactions between the cationic nitrogen and the anionic boron than those between the boron and the alkali metal centres. Finally, a study of the structures of alkali metal hydrated and THF-solvated BArF salts showed that the interactions between the metal centre and the surrounding atoms depend not only on the size of the alkali metal centre but also on the occupancy of the first coordination sphere.