Acetonitrile-tetrabutylammonium hexafluorophosphate

Electrochemical fluorination 168,169> is a commercial process for perfluorina-tion of aliphatic compounds. The reaction is performed in liquid hydrogen fluoride -potassium fluoride at a nickel anode. The mechanism is not known free fluorine cannot be detected during electrolysis, so it seems probable that fluorination is a direct electrochemical reaction. Theoretically, hydrogen fluoride-potassium fluoride should be a very oxidation-resistant SSE, and it might well be that the mechanism is analogous to that proposed for anodic acetamidation of aliphatic compounds in acetonitrile-tetrabutylammonium hexafluorophosphate 44 K... 

In 1985, Sullivan et al. reported a voltammetric study on (Bipy)Re[CO]3Cl in acetonitrile with tetrabutylammonium hexafluorophosphate (TBAHFP) as the supporting electrolyte. 

Figure 12.4 Cyclic voltammograms of 1 mM diphenylanthracene in acetonitrile containing 0.01 M tetrabutylammonium hexafluorophosphate. Scan rate 115 V/s. Solid line voltammogram recorded at a disk electrode with a 14 /xm radius. Dashed line voltammogram recorded at a disk electrode with a 0.91 mm radius.

Figure 12.5 Cyclic voltammograms for the reduction of 1 mM cobaltocenium (Cp2Co+) hexafluorophosphate and oxidation of 1 mM ferrocene (Cp2Fe) in acetonitrile recorded at a band electrode (width = 4.6 / m) at a scan rate of 10 mV s 1. The supporting electrolyte is tetrabutylammonium hexafluorophosphate at (A) 0.02 M, (B) 0.2 mM, (C) 2.0 mM, and (D) 20 mM. [From Ref. 68, reprinted with permission of the copyright holder.]...

MeNP, 2-methyl-2-nitropropane NPent, 1-nitropentane NPh, 3-nitrophenol COT, cycloocta-tetraene TPE, tetraphenylethylene TBAP, tetrabutylammonium perchlorate TEABr, tetraethyl-ammonium bromide TBAPIy, Tetrabutylammonium hexafluorophosphate MeCN, acetonitrile DMSO, dimethylsulfoxide DCM, dichloromethane [42]... 

Fig. 25 Cyclic voltammogram of complex 45 measured in acetonitrile in the presence of 0.1 M tetrabutylammonium hexafluorophosphate as supporting electrolyte with 100 mV s 1 scan rate. The black line shows the scan between - 2.4 to 1 V, and the gray line between - 2.8 to 1 V. The observed irreversible new wave at around - 1.35 V is due to unknown product that is formed when scanning to more negative potential...

Diphenyl ditellurium was electrochemically reduced to benzenetellurolate in acetonitrile with sonication in anH-type cell. Tetrabutylammonium hexafluorophosphate served as the electrolyte. The cathode was a cylindrical graphite cloth and the anode a platinum grid. The cathodic solution was purged with argon. The potential had to be changed from — 1.20 to — 2.35 V during the reduction1-3. 

The electropolymerization of ferrocene/thiophene conjugates [65] was conducted by oxidation on a Pt electrode and led to the deposition of a monolayer of poly (thiophene). The electropolymerization was performed from several solution systems, such as tetrabutylammonium hexafluorophosphate/acetonitrile and lithium perchlorate/acetonitrile, at a concentration of 0.1 M. Constant potential experiments (+ 2.0 V) for a definite time were used to effect polymerization. Polymerization was also attempted using cyclic voltammetry (repeatedly sweeping from 0.0 to + 2.5 V) and pulse potential (potential stepped from 0.0 to 2.0 V and back to 0.0 V). 

Figure 1. Cyclic voltammetry resulls for a 0.001 M solution of Co(terpy)(bipy)]+ complex in acetonitrile with 0.10 M tetrabutylammonium hexafluorophosphate as supporting electrolyte. Scan rate was 0.10 Volts/sec in all experiments. Potentials are referenced vs. silver/0.010 M silver nitrate in acetonitrile, (a) Impure complex under nitrogen, (b) impure complex under oxygen, (c) purified complex under nitrogen, and (d) purified complex under oxygen.

The electrolyte, added to enhance conductivity and to minimize double-layer and migration current effects, is chosen on the basis of solubility in a given solvent as well as inertness toward the electroactive substance and its electrolysis products. There are of course many choices of electrolyte for use in aqueous solution. The tetraalkylammonium salts are the most commonly used non-aqueous electrolytes. Tetrabutylammonium tetrafluoroborate (TBATFB) and tetrabutylammonium hexafluorophosphate (TBAHFP) are recommended by Fry and Britton, who note that TBAHFP in acetonitrile has a particularly large useful potential range of +3.4 to —2.9 V (vs. SCE). 

The observed potential changes did not exceed few mV if measurements have been performed in acetonitrile solution and cmicentratimi of tetrabutylammonium hexafluorophosphate changed in the range 0.001—1 M. Such anhydrous bUayers could be promising candidates for the reference electrodes to be applied in organic solvents. 

Electrochemical measurements were carried out at room temperature ( 25 °C) by using a Metrohm E/506 Polarecord, a Metrohm E/612 VA scanner, and a Hewlett-Packard 7044 x-y recorder. Cyclic voltammograms were obtained in acetonitrile solution by using a microcell equipped with a stationary platinum disk electrode, a platinum disk counter electrode, and a SCE reference electrode with tetrabutylammonium hexafluorophosphate as supporting electrolyte. In all cases [Ru(bpy)3](PFg)2 was used as a standard, taking its oxidation potential equal to +1260 mV vs SCE [22, 23] The electrochemical window examined was between +2.0 and -2.0 V. Scanning speed was 200 mV s. All the reported values are vs SCE. Half-wave potentials were calculated as an average of the cathodic and anodic peaks. 

Dibenzyl ditellurium was obtained in 70% yield by alkylation of the electrochemically generated ditelluride dianion with benzyl chloride in acetonitrile3. The ultrasonically promoted electrochemical reduction of tellurium powder was performed in H-type cells with the compartments separated by glass frits. Acetonitrile served as solvent and tetrabutylammonium tetrafluoroborate or hexafluorophosphate as the supporting electrolyte. At potentials beyond -1.1 V the dark-red ditelluride dianion is formed in the cathode and in the central compartment3. 

Stoddart et al. have recently used iodide-catalyzed reversible nucleophUic substitution in the thermodynamically controlled assembly of a donor-acceptor [3]catenane 20 (Figure 1.31) [37]. Exposure of cyclobis-(paraquat-4,4 -biphenylene) tetrakis-hexafluorophosphate (18) to 2 equiv. of bis-para-phenylene [34]crown-10 (19) in the presence of tetrabutylammonium iodide in acetonitrile at 80 °C led to the formation of [3]catenane 20 in 80% yield (Scheme 1.9). The Sn2 reaction... 

Polyselenophene (Fig. 16c) has been prepared. However, due to the difficulty in obtaining the monomer, the polymer has not been extensively investigated. Polymers of selenophene prepared electrochemically under appropriate conditions yield films with maximum conductivities of 10"- S cm [330,331]. Samples of p-doped selenophene produced chemically have conductivities on the same order of magnitude [332]. Applying 3-10 V between two electrodes in an electrolyte of 0.1 to 1 M lithium tetrafluoroborate or lithium perchlorate dissolved in benzonitrile or propylene carbonate gives polyselenophene films, as does the combination of tetrabutylammonium tetrafluoroborate in benzonitrile. However, other salts such as lithium hexafluoroarsenate, lithium hexafluorophosphate, tetrabutylammonium perchlorate, or silver perchlorate in combination with solvents such as acetonitrile or nitrobenzene were reported to produce either powders or no products at all [330,331,333]. 

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