Synthesis and thermal properties of salts comprising cationic bis(oxazoline)-AuIII complexes and fluorinated anions

Abstract

Salts comprising cationic bis(oxazoline) (box)-AuIII complexes and fluorinated anions were synthesized and their thermal properties were investigated. Cations that contain box ligands with butyl substituents (butyl-box) were used with either achiral-(R,S) ([1]+) or chiral-(S,S) ([2]+) configurations. [1][Tf2N] (Tf2N−=bis(trifluoromethanesulfonyl)amide) is a solid that can also be classified as an ionic liquid (Tm=62°C, Tg=−11°C). [1]X and [2]X (X=SbF6− and BF4−) exhibit melting points higher than 100°C, where [1]X exhibits a higher melting point than [2]X. A salt with an ethyl-box ligand ([3][SbF6]) exhibits no melting up to its decomposition temperature of 267°C. Crystal structure determination revealed that the achiral cation in [1][BF4] has a bent structure. The potential utility of [1][Tf2N] for catalysis was demonstrated by the catalytic formation of an acetal from an alkyne.