Trihexyl-tetradecyl phosphonium

Fig. 4 Resonant frequency changes with time due to repetitive FIA melamine injections, for the MIP-QCM chemosensor. Melamine concentration is indicated with number at each curve. Inset shows FIA calibration plots for (1) melamine and its interfering compounds, such as (2) ammeline, (3) cyanuric acid, and (4) cyromazine. Volume of the injected sample solution was 100 pL. The flow rate of the 1 mM FIC1 carrier solution was 35 pL min-1. The MIP film was prepared by electropolymerization of 0.3 mM bis(2,2 -bithienyl)-benzo-[18-crown-6]methane functional monomer and 0.3 mM 3,3 -bis[2,2 -bis(2,2 -bithiophene-5-yl)]thianaphthene cross-linking monomer, in the presence of 0.1 mM melamine, in the trihexyl(tetradecyl)phosphonium tris(pentafluor-oethy 1)-trifluorophosphate ionic liquid ACN (1 1 v/v) solution, which was 0.9 mM in trifluoroacetic acid (pH = 3.0). The melamine template was extracted from the MIP film with 0.01 M NaOH before the determinations (adapted from [134])...

Phosphonium ionic liquids can be a reactive carrier of organic acids and form effective SLM, as was found recently [183]. SLM with ionic liquid trihexyl-(tetradecyl) phosphonium bis 2,4,4-trimethylpentylphosphinate (Cyphos IL-104) had stable performance in pertraction of lactic acid for 5.3 days [44, 45], which is promising. 

The first example of a Heck reaction in a molten salt stems from as early as 1996 when tetraalkylammonium and phosphonium halides were used as reaction media for the coupling between arylhalides and n-butyl acrylate. Particularly good results were achieved in trihexyl(tetradecyl)phosphonium chloride, both in terms of reactivity and ease of product isolation. 

Trihexyl(tetradecyl)phosphonium bis(trifluoromethylsulfonyl)imide C3.H33F3NO/S3 460092-03-9 764.002 1.067 ... 

Trihexyl(tetradecyl)phosphonium tris(pentafluoroethyl)trifluoro- C38H63F13P2 928.866 <-50 1.18 ... 

N, N, N, N -trimethylbutylammonium l-ethyl-3-methyl-imidazolium l-n-hexyl-3-methyl-imidazolium l-n-butyl-3-methyl-imidazolium l-ethyl-3-methyl-imidazolium l-n-butyl-3-methyl-imidazolium l-n-hexyl-3-methyl-imidazolium trihexyl (tetradecyl) -phosphonium trihexyl (tetradecyl) -phosphonium... 

One of the earliest reports on use of a phosphonium salt as an IL in such a process was that of Kaufmann and co-workers (9). In this work, the use of tri-butyl(hexadecyl)phosphonium bromide as a recyclable medium for the palladium-mediated Heck coupling of aryl halides with acrylate esters was reported (9). While these reactions proceeded without the use of an additive ligand, elevated temperatures (100 °C) were required and the process was most efficient only with more activated aryl halides [Eq. (1)]. More recently, the use of trihexyl(tetradecyl)-phosphonium chloride (Cyphos IL 101) has been reported as a useful medium for the Suzuki cross-coupling of aryl halides with boronic acid derivatives [Eq. (2)] [10]. In this process, a soluble palladium precursor such as Pd2(dba)3-CHCl3 was dissolved in the phosphonium salt, forming a dark orange solution. This solution was stable in the absence of oxygen for an extended period of time and could be... 

Phosphonium salts are very thermally stable, as illustrated by the TGA plots for trihexyl(tetradecyl)phosphonium chloride (CYPHOS IL 101) in Figure 1. Under inert conditions, the weight loss onset occurs at approximately 310 °C whereas, even imder oxidative conditions, the onset occurs at approximately 280 °C. These results are comparable to those for imidazohum salts with the same anion, but much higher than those for the corresponding ammonium salts [61[. 

Figure TGA plots for trihexyl tetradecyl)phosphonium chloride (CYPHOS IL 101). Heating rate = 5 °C min under air and dinitrogen atmospheres [51].

Figure 2 Isothermal TGA plots for trihexyl (tetradecyl)phosphonium chloride [62].

The viscosities of phosphonium-based ILs are generally greater that those of imidazoKum salts. However, the addition of even minor levels of solutes restdts in dramatic lowering of the viscosity [63]. Additionally, the viscosity of ILs decreases exponentially with temperature. These effects are illustrated in Figure 3, which contains viscosity/temperature plots for trihexyl(tetradecyl)phosphonium chloride, initially containing 0.8% water. In the presence of a reactive substrate or reaction product and having been heated to a typical reaction temperature of 80 °C, phosphonium IL systems become water-like in viscosity. 

The viscosity is also a function of the anion. Bistriflamide and dicyanamide anions result in relatively low viscosities, as shown in Figure 4. Given the same trihexyl-(tetradecyl)phosphonium cation, the viscosity of the dicyanamide salt is an order of magnitude lower than that of the salt with a chloride anion. Solute and temperature have a similar viscosity lowering effect. 

Figures Effect of solute and temperature on trihexyl (tetradecyl) phosphonium chloride viscosity.

In general, salts with alkylphosphonium cations are less dense than water. Densities as a function of temperature for trihexyl(tetradecyl)phosphonium chloride (CYPHOS IL101), trihexyl(tetradecyl)phosphonium dicyanamide (CYPHOS IL105) and trihexyl(tetradecyl)phosphonium bis(2,4,4-trimethylpentyl)phosphinate (CYPHOS IL 104) are found in Figure 5. Phosphonium salts with aromatic anions such as triisobutyl(methyl)phosphonium tosylate (CYPHOS IL 106) have densities greater than that of water. The density of trihexyl(tetradecyl)phosphonium hexa-fluorophosphate (CYPHOS IL 110) is unique in that, depending on the temperature, it may be greater or less than that of water. 

Figures Cyclic voltammogram for trihexyl(tetradecyl)phosphonium bistriflamide.

Finally, taking into account the growing general interest in ILs, these compounds have also become the subject of computational studies, e.g., molecular dynamics simulations were performed for one of the phos-phonium-based ILs, namely trihexyl(tetradecyl)phosphonium bis(trifluoro-methylsulphonyl)imide. 

Kogelnig, D., Regelsberger, A., Stojanovic, A., Jirsa, F., Krachler, R., and Keppler, B. K. 2011. A polymer inclusion membrane based on the ionic liquid trihexyl(tetradecyl)phosphonium chloride and PVC for solid-liquid extraction of Zn(II) from hydrochloric acid solution. Monatsheftefur Chemie 142 769-772. 

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