Syntheses and Properties of Fluorous Quaternary Phosphonium Salts that Bear Four Ponytails; New Candidates for Phase Transfer Catalysts and Ionic Liquids
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The fluorous tertiary phosphine [Rf6-(CH2) 2]3P [Rfn = CF3(CF2) n-1] and excess PhCH2Br, CH3(CH 2)3OSO2CF3, or R f6(·CH2)2OSO2CF3 react (CF3C6H5, 45-110°C) to give the phosphonium salts (PhCH2)[Rf6(CH2) 2]3P+ Br- (2, 71%), [CH 3(CH2)3] [Rf6(CH2) 2]3P+ CF3SO3- (3, 65%), or [Rf6-(CH2)2]4P + CF3SO3- (4, 83%). The phosphines [Rf6-(CH2)2]2[Rf8(CH 2)2]P and [Rf8(CH2) 2]3P are similarly elaborated with Rf6(CH 2)2I, Rf8(CH2)2I, or Rf8-(CH2)2Br (DMF, 115°C) to [R f8(CH2)2]4-x[Rf6-(CH 2)2]xP+ I- (x = 3, 7; 2, 8; 1, 9; O, 10) or [Rf8-(CH2)2] 4P+ Br- (80-60%). The salts exhibit melting points between UO°C and 43°C, with lower values favored by less symmetrical cations, Rf6 segments, and triflate and bromide anions. Solubilities decrease in the solvent sequence CF3C6F 5 (all salts at least moderately soluble, room temperature) > acetone > THF > CF3C6H5 > CF 3C6F11 > CH3C6H 5, Et2O, CH2Cl2, hexane (all salts insoluble at elevated temperatures); some appreciably increase upon heating. Partition coefficients are very biased towards fluorous phases (> 93: < 7). The salts can be quite efficient at extracting picrate from water into CF3C6F5 (97-86% for 2, 4, 9, 10) or CF 3C6H5 (85-66% for 2-4), demonstrating their potential for phase transfer catalysis. A CF3C6F 5 solution of Rf8(CH2)3I and aqueous NaCl react at 100°C in the presence (but not the absence) of 9 to give Rf8(CH2)3Cl. © 2006 Wiley-VCH Verlag GmbH & Co. KGaA.
author list (cited authors)
Emnet, C., Weber, K. M., Vidal, J. A., Consorti, C. S., Stuart, A. M., & Gladysz, J. A.