Alkylcyanoborate Anions: Building Blocks for Fluorine‐Free Low‐Viscosity, Electrochemically and Thermally Stable Ionic Liquids

Abstract

A set of mixed‐substituted potassium alkylcyano‐ and alkylcyanofluoroborates has been synthesized using easily accessible starting compounds and characterized by elemental analysis, NMR and vibrational spectroscopy, and mass spectrometry. In addition, single‐crystal structures of salts of the cyanoborate anions have been derived from X‐ray diffraction experiments. The 1‐ethyl‐3‐methylimidazolium room temperature ionic liquids ([EMIm]+‐RTILs) with the new borate anions have been synthesized and their physicochemical properties, that is, high thermal and electrochemical stability, low viscosity, and high conductivity, have been compared to the properties of related [EMIm]+‐RTILs. The influence of the different alkyl substituents at boron has been assessed. The exemplary study on the properties with the [EMIm]+‐ILs with the mixed water stable alkylcyanoborate anions points towards the potential of these fluorine‐free borate anions, in general.

Nickel(II) Cyanoborates and Cyanoborate-Ligated Nickel(II) Complexes

“…A major focus of cyanoborate chemistry has been devoted to the development of room temperature ionic liquids (RTILs) that often exhibit low viscosities and high specific conductivities. − In combination with the typical high stability of cyanoborates ( vide supra ), these RTILs comprise versatile compounds for different materials applications, especially for electrochemical devices such as dye-sensitized solar cells (DSSCs, Grätzel cells), ,− batteries, − and supercapacitors. − …”

NHC-ligated nickel(ii) cyanoborate complexes and salts

“…6 In the last years significant advances have been made on the functionalization of such building blocks giving access to a broad variety of cyanoborate anions, bearing for example hydrido, fluorido, perfluoralkyl, alkoxy, alkyl, vinyl, alkynyl or other substituents. 1,7 Just recently, we reported the synthesis of N -tricyanoborane substituted anionic N -heterocyclic carbenes (NHCs) and anionic cyclic (alkyl)(amino)carbenes (cAACs). 8 For example, the 1-methyl-3-(tricyanoborane)imidazolin-2-ylidenate anion ( A ), i.e.…”