Chlorocyanoborates: Synthesis, Spectroscopic and Structural Characterization, and Properties of Ionic Liquids

A set of first mixed chlorocyanoborates was synthesized and fully characterized by elemental analysis, NMR and vibrational spectroscopy. Two different synthetic approaches were developed: Exchange of chlorine against CN in case of [BCl3(CN)]– and reaction of [BHx(CN)4–x]– with Cl2 or tBuOCl for the generation of [BClx(CN)4–x]– (x = 1, 2). The single‐crystal structures of [Ph4P][BCl2(CN)2] and [Ph4P][BCl3(CN)] were derived from X‐ray diffraction experiments. [EMIm][BClx(CN)4–x] (x = 1–3) and [BMPL][BClx(CN)4–x] (x = 1, 2) were found to be low‐viscosity room temperature ionic liquids. [EMIm][BCl(CN)3] (18.6 mPa·s) and [EMIm][BCl2(CN)2] (19.6 mPa·s) are even less viscous than the well‐known [EMIm][B(CN)4] (EMIm‐TCB, 22.6 mPa·s). Mono‐ and dichlorocyanoborates were studied by CV and found to provide large electrochemical windows. Especially [EMIm][BCl(CN)3] reveals a high specific conductivity (14.1 mS cm–1).