An Ionic Liquid Designed for Coordination Chemistry Revisited: Synthetic Routes and Safety Tests for 1-Ethyl-3-methylimidazolium Perchlorate ([emim][ClO4])

The colourless room-temperature ionic liquid 1-ethyl-3-methylimidazolium perchlorate, [emim][ClO4], was revisited for reasons of its hydrophilic character and its weak coordinating ability. In this study, [emim][ClO4] was synthesized from the cheaper ionic liquid 1-ethyl-3-methylimidazolium ethyl sulfate, [emim][EtSO4], by way of direct and indirect membrane-assisted anion metathesis. Both synthetic methods, as alternatives to the metathesis of silver perchlorate and [emim] halides, are compared and discussed in detail. In addition, some physicochemical parameters were determined to characterize the ionic liquid. With respect to the hazardous nature of organic perchlorates, the thermal stability as well as the impact and friction sensitivity of [emim][ClO4] were tested according to the UN Test Series 3a-3d.