Preparation by electrochemical

Many perfluoroaUphatic ethers and tertiary amines have been prepared by electrochemical fluorination (1 6), direct fluorination using elemental fluorine (7—9), or, in a few cases, by fluorination using cobalt trifluoride (10). Examples of lower molecular weight materials are shown in Table 1. In addition to these, there are three commercial classes of perfluoropolyethers prepared by anionic polymerization of hexafluoropropene oxide [428-59-1] (11,12), photooxidation of hexafluoropropene [116-15-4] or tetrafluoroethene [116-14-3] (13,14), or by anionic ring-opening polymeriza tion of tetrafluorooxetane [765-63-9] followed by direct fluorination (15). 

The longer perfluoroalkanesulfonic acids are hydroscopic oily Hquids. Distillation of the acid from a mixture of its salt and sulfuric acid gives a hydrated mixture with melting points above 100°C. These acids show the same general solubiUties as trifluoromethanesulfonic acid, but are insoluble in ben2ene, heptane, carbon tetrachloride, and perfluorinated Hquids. AH of the higher perfluoroalkanesulfonic acids have been prepared by electrochemical fluorination (20). 

Carbonyl sulfonyl fluorides of the formula FC0(CF2) S02F have been prepared by electrochemical fluorination of hydrocarbon sultones (41,42). More commonly in a technology pioneered by Du Pont, perfluoroalkanecarbonyl sulfonyl fluorides are prepared by addition of SO to tetrafluoroethylene followed by isomerization with a tertiary amine such as triethylamine (43). 

Petfluotoalkanesulfonic acids also show high acidity. The parent trifluoromethanesulfonic acid (triflic acid), CF SO H, is commercially prepared by electrochemical fluorination of methanesulfonic acid (214). It has an value of —14.1 (215,216). The higher homologues show slightly decreasing acidities. 

It has recently been reported that a molecule, claimed to contain a high concentration of conjugated alkyne units, can be prepared by electrochemical reduction of polytetrafluoroethylene (PTFE) [32,33]. The reduction is carried out using magnesium and stainless steel as anode and cathode respectively. The electrolyte solution contains THE (.30 cm ), LiCI (0.8 g) and FeCl2 (0.48 g). A 10 X 10 nm PTFE film, covered with solvent, is reduced to carbyne (10 V for 10 h)... 

Figure 6. Thermogravimetric curves for I l08,Li0 ]5NiOi in air. The heating and cooling rates were 5 °Cmin 1. The sample was prepared by electrochemical oxidation of LiNi02 without addition of conductive binder to 4.8V using an Li/LiNiO, cell, washed with DME and THF, and dried under vacuum at room temperature.

Torimoto T, Takabayashi S, Mori H, Kuwabata S (2002) Photoelectrochemical activities of ultrathin lead sulfide films prepared by electrochemical atomic layer epitaxy. J Electroanal Chem 522 33-39... 

The influence of Pt modihcations on the electrochemical and electrocatalytic properties of Ru(OOOl) electrodes has been investigated on structurally well-defined bimetallic PtRu surfaces. Two types of brmetalhc surfaces were considered Ru(OOOl) electrodes covered by monolayer Pt islands and monolayer PtRu/Ru(0001) surface alloys with a highly dispersed and almost random distribution of the respective surface atoms, with different Pt surface contents for both types of structures. The morphology of these surfaces differs significantly from that of brmetaUic PtRu surfaces prepared by electrochemical deposition of Pt on Ru(0001), where Pt predominantly exists in small multilayer islands. The electrochemical and electrocatal5d ic measurements, base CVs, and CO bulk oxidation under continuous electrolyte flow, led to the following conclusions ... 

Acyclic phosphoranes. - A number of difluorotris(perfluoro-alkyl)phosphoranes (7) have been prepared by electrochemical fluor-ination of trialkylphosphine oxides (6) in anhydrous HF17. The phosphoranes are conveniently converted into the perfluoroalkyl-phosphine oxides (8) by reaction with hexamethyldisiloxane and the phosphoranes are regenerated by treatment of (8) with HF. 

The iV-( -nitrophcnyl)pipcrazinc-2-carbonitrilc 251 (Y = NBOC) was reductively cyclized to the tricyclic /V-oxides 252 (Y = NBOC) either by catalytic hydrogenation, or by electrochemical reduction. Electrochemical reduction gave lower yield. Compounds 251 were prepared by electrochemical cyanation of the iV-(o-nitrophenyl)piperazine 250. The jV-oxides 252 were further hydrogenated to the 2,3,4,4 ,5,6-hexahydro-l//-pyrazino[l,2- ]quinoxaline 253 (Y = NBOC) (Scheme 46) <2001EJ0987>. 

Nickel hexacyanoferrate (NiHCF) films can be prepared by electrochemical oxidation of nickel electrodes in the presence of hexacyanoferrate(III) ions,141 or by voltammetric cycling of inert substrate electrodes in solutions containing nickel(II) and hexacyanoferrate(III) ions.142 NiHCF films do not possess low-energy intervalent CT bands, however, when deposited on ITO they are observed to reversibly switch from yellow to colorless on electroreduction.143... 

The structure of a polycrystalline electrode depends on its preparation. Usually toe rough electrodes are prepared by electrochemical deposition of a given metal onto a suitable substrate. Microcrystals present in polycrystaUine samples are randomly oriented on the surface. Most likely, not only basal but also higher MiUer-index planes should be considered in anticipating toe final structure of the electrode surface. It was shown that the stmcture of the platinized platinum surface depends strongly on toe platinization conditions, e.g., on toe concentration of the platinization... 

It is quite often possible to prepare hydroxypyridinone complexes directly by one-pot synthesis from the appropriate hydroxypyranone, amine, and metal salt 90-92). They can also be prepared by reacting complexes such as P-diketonates with hydroxypyridinones (see e.g., Ce, Mo later). Several maltolate complexes, of stoichiometry ML2, ML3, ML4, or MOL2, have been prepared by electrochemical oxidation of the appropriate metal anode, M — a first-row d-block metal (Ti, V, Cr, Mn, Fe, Co, Ni), In, Zr, or Hf, in a solution of maltol in organic solvent mixtures 92). Preparations of, e.g., manganese(III), vanadium(III), or vanadium(V) complexes generally involve oxidation... 

ETEROAROMATics FURAN AND THIOPHENE. The chemical transformation of thiophene at high pressure has not been studied in detail. However, an infrared [441,445] study has placed the onset of the reaction at 16 GPa when the sample becomes yellow-orange and the C—H stretching modes involving sp carbon atoms are observed. This reaction threshold is lower than in benzene, as expected for the lower stability of thiophene. The infrared spectrum of the recovered sample differs from that of polythiophene, and the spectral characteristics indicate that it is probably amorphous. Also, the thiophene reaction is extremely sensitive to photochemical effects as reported by Shimizu and Matsunami [446]. Thiophene was observed to transform into a dark red material above 8 GPa when irradiated with 50 mW of the 514.5-nm Ar+ laser line. The reaction was not observed without irradiation. This material was hypothesized to be polythiophene because the same coloration is reported for polymeric films prepared by electrochemical methods, but no further characterization was carried out. 

Mercury film electrode (MFE) A thin layer of elemental mercury, usually on graphite, prepared by electrochemical deposition from an aqueous solution of mercury(ii). 

This oxidation state which resembles Cu(II) may be prepared by electrochemical, photochemicalor pulse radiolytic reduction of nickel(II). Nickel(I) macrocycles are powerful reductants and their spectra and redox potentials have been measured. The reactions of the Ni(I) complexes Ni(tmc) 10 and 11 with RX are similar. 

The polymer CgoPt has also been made by using Pt(l,5-cyclooctadiene)2 [88], Various CjoM polymer films have been prepared by electrochemical reduction of transition metal complexes of the central metal Pd(II), Pt(II), Ir(I), Rh(l), Rh(ll), Rh(lll) and Au(l) [89, 90]. The metal complex in solution is first electrochemicaUy reduced to the zerovalent metal, which then forms polymer films containing M Coo on the electrode. 

A tungsten tip, prepared by electrochemical etching, with a perfectly smooth end of very small radius observed by SEM or TEM, would not provide atomic resolution immediately. 

Polyfluorinated furans have also been prepared by electrochemical methods in which the substrates are treated with CoF3 (or the less reactive KCoF4), followed by base-induced elimination of HF [70JCS(C)2146 73MI1]. 

A series of adducts of organocadmium halides with neutral bidentate ligands RCdX L (L = dioxane, bipy or phen) have been prepared by electrochemical oxidation of the metal in the presence of L and the alkyl halide. In the additional presence of [N(n-propyl)4]X, salts of the [RCdX2] anion may be isolated.1064... 

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