Synthesis and characterization of fluorinated phosphonium ionic liquids

A wide variety of phosphonium ionic liquids containing fluorous ponytails R f n (R f n = –(CF 2 ) n –1 CF 3 ; n = 4, 6, 10) are synthesized by the reaction of R f n -(CH 2 ) 2 -I with trialkylphosphines (R 3 P; R = Me, n Bu, n Oct). The efficacy of multiple metathetical routes to anion exchange have been investigated, thus the corresponding BF 4 – , PF 6 – , tosylate (OTs – ) and triflate (OTf – ) derivatives have also been prepared. All compounds have been comprehensively characterized by multinuclear NMR spectroscopy, ESI-MS, DSC, and TGA/SDTA, and in the case of [Me 3 PCH 2 CH 2 R f4 ][I] by single crystal X-ray diffraction. These materials range from high melting solids (e.g., [Me 3 P(CH 2 ) 2 R f4 ][I] T m = 195 °C) to very low melting liquids (e.g., [ n Oct 3 P(CH 2 ) 2 R f4 ][OTf] T g = –64 °C), and they all have high thermal decomposition points (295 to 394 °C). Incorporation of the more weakly coordinating BF 4 – and PF 6 – yielded a significant increase in the melting point of the materials, in contrast to OTf – and OTs – derivatives, which all exhibited significantly depressed melting points.