Ionic Liquids: Synthesis and characterization of triphenylphosphonium tosylates

Ionic liquids are currently attracting considerable interest from chemists, partly due to their potential as "green" alternatives to volatile molecular organic solvents. Phosphonium ionic liquids have received much less attention than ammonium salts in the past, but the situation is changing. The salts are applied in the liquid state but in this work, salts with higher melting points than is generally the case are investigated. They are solid at room temperature, thus enabling facile separation of liquid reaction products. Nine triphenyl-phosphonium tosylates have been prepared and characterised; their crystal structures have been determined and their melting points have been scrutinized, showing some sensitivity to the duration of drying. The structural information is expected to be invaluable in the understanding of the properties of the molten state. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006).