HexaChloroantimonic acid

Hexachloroantimonic acid may alternatively be prepared by adding chlorine to SbjOs suspended in concentrated hydrochloric acid." For the precipitation of the ammonium hex-achloroantimonate solution prepared in either way may be used directly without isolating the hexachloroantimonic acid hydrate. 

The SbaOs reqviired for the preparation of chemically pure Sb is made by hydrolysis of hexachloroantimonic acid. The latter is dissolved in some double-distilled water, and the cold solution is diluted with more water. Then C. P. ammonia is added and the solution is heated on a water bath until the SbgOg precipitate settles. Decantation follows, then repeated washir witti chemically pure water and another decantation. Finally, the precipitate is suction filtered through a paper filter. The substance is dried in a dish by heatup on a water bath. 

When using a cation source in conjunction with a Friedel-Crafts acid the concentration of growing centers is most often difficult to measure and remains unknown. By the use of stable carbocation salts (for instance trityl and tropyhum hexachloroantimonate) the uncertainty of the concentration of initiating cations is eliminated. Due to the highly reproducible rates, stable carbocation salts have been used in kinetic studies. Their use, however, is limited to cationicaHy fairly reactive monomers (eg, A/-vinylcarbazole, -methoxystyrene, alkyl vinyl ethers) since they are too stable and therefore ineffective initiators of less reactive monomers, such as isobutylene, styrene, and dienes. 

The ready separation of the hexachloroantimonate salts of various cation radicals is possible owing to their insolubility in diethyl ether (or hexane) under conditions in which the reduced antimony(III) chloride is highly soluble. In the case of EA+ SbClg", the isolated product is quite pure as determined by iodometric titration. However in many other cases, the Lewis acid SbCl5 effects... 

Scheme 5.1 Mechanism of thioglycoside activation (a) by thiophiles X1 such as /V-bromosuccinimicle (NBS), 11,12 methyl triflate,13 dimethyl(methylthio)sulfonium triflate (DMTST),14 phenylselenyl triflate (PhSeOTf),17,18 iV-iodosuccinimide/triflic acid (MS/TfOH),19 20 and iodonium di-sym-collidine perchlorate (IDCP)21 (b) by tris(4-bromophenyl)ammoniumyl hexachloroantimonate (TBPA,+)25 and (c) via anomeric sulfoxides.26 The stereochemical outcome of these glycosylations follows the same general trends as with many other glycosyl donor/promoter combinations (m-CPBA = mcta-chloroperbenzoic acid).

The electron-transfer reactions between the /3-cyclodextrin (/3-CD) N-substituted phenothiazine derivatives and /3-CD.ATPO (4-acetoxy-2,2,6,6-tetramethyl-1-oxopiperidinium hexachloroantimonate) were found to be influenced by the conformations of the phenothiazine derivatives restricted by the /3-CD cavity. N-Phenylphenothiazine (PPT) and A-phenylethylphenothiazine (PEPT), included by /3-CD, can transfer an electron to the /S-CD.ATP complex. No electron transfer was observed between the /3-CD.A-benzylphenothiazine (/3-CD.BPT) complex under the same conditions. The conformation of the /3-CD.BPT complex is such that the oxidation centre was shielded by the /3-CD wall and the substituent. However, electron-transfer reactions between y-CD.BPT and /3-CD.ATP and nitric acid occurred. ... 

Table 5-1 shows the various kinetic parameters, including k+ and kp, in the polymerization of styrene initiated by triflic acid in 1,2-dichloroethane at 20°C. Data for the polymerization of isobutyl vinyl ether initiated by trityl hexachloroantimonate in methylene chloride at 0°C are shown in Table 5-2. Table 5-3 shows values for several polymerizations initiated... 

At low temperatures in inert solvents (such as methylene dichloride) a controlled polymerization can be effected using various acids and alkylating agents. These initiators include boron trifluoride etherate, triethylaluminum, trityl hexachloroantimonate, triethylam-monium hexachloroantimonate, diethyloxonium hexafluoroantimonate, p-toluenesulfonic acid and diethylzinc or cadmium-1,2-dioI complexes. Crystalline, high molecular weight... 

A radical-cation initiated intramolecular cycloaddition of 3 to 4 has been reported to occur using tris(4-bromophenyl)amminium hexachloroantimonate (TBAH).22 A number of Bronsted acids including trifluoroacetic acid can also effect this reaction. 

Studies of the reactivity of transition metal cyclopropenylium complexes are negligible. A single example on the acid hydrolysis of the hexachloroantimonate palladium dimer complex [(i-Pr2N)2C3(PdCl)]2-2SbCl6, and its demetallation using SbCl5, is outlined in equation 293. 

Other Substituted Diazonium Ions. A series of aminodiazonium ions have been prepared under superacidic conditions [Eq. (4.141)]. Schmidt495 described the preparation and IR spectra of protonated hydrazoic acid 212 and methylazide as their hexachloroantimonate salts. Olah and co-workers496 have carried out a comprehensive study on aminodiazonium ions (protonated azides) by H, 13C, and 15N NMR spectroscopy. Even the electrophilic aminating ability of aromatics of 212 has been explored.496 The tetrachloroaluminate salt of 212 has also been prepared496... 

Methylaluminum dichloride, 7 a-Methylamino acids, 192 Methyl a-arylacetates, 268 Methyl a-arylalkanoates, 471 a-Methylbenzylamine, 411 Methyl bis(methylthio)sulfonium hexachloroantimonate, 335-336 N-Methyl-N-(t-butyldimethylsilyl)acetamide, 336... 

Methylbis(methylthio)sulfonium hexachloroantimonate ([CH3S(SCH3)2][SbCl6]) was isolated from the reaction mixture at -40°C by the oxidation of nonpoly -merizable dimethyl disulfide [86], This result suggests that the phenylbis(phenyl-thio)sulfonium cation is produced by the oxidation of diphenyl disulfide in the acidic reaction mixture [87-89], This cation acts as the active species for the polymerization and electrophilically reacts with the / -position of the benzene ring to yield PPS [90],... 

In the past decade, there has appeared only one report, which can be classified under this heading, on the monodeoxygenation of spiro-adamantane-l,2-dioxetanes induced by catalytic amounts of tris-(2,4-dibromophenyl)-aminium hexachloroantimonate <1998T6939>. An electron-transfer mechanism from the aminium salt has been proposed for the observed formation of various ketones. Reports citing the electrophilic ring opening of dioxetanes by boron trifluoride, trifluoroacetic acid, and various other Lewis acids have been summarized in CHEC-II(1996) <1996CHEC-II(1B)1041>. 

The cyclization reactions of chloro-substituted 2-azonioallene hexachloroantimonate salts with dimethylbarbituric acid (204) give highly substituted pyrimido[5,4-e][l,3]oxazinium hexachloroantimonate salts (205) and (207). Some of them could be converted into pyrimido[4,5-c/]pyrimidines (206) (Scheme 35) <92S59i>. 

Pentathiazyl tetrachloroaluminate(l —) and, to a lesser extent, penta-thiazyl tetrachloroferrate(l —) are moisture-sensitive both are soluble in thionyl chloride, anhydrous formic acid, and concentrated sulfuric and nitric acids. On dissolution in acid, hydrogen chloride is evolved because of decomposition of the anion. The solution in anhydrous formic acid can be used to prepare other salts by metathesis.7 The hexachloroantimonate(l —) undergoes almost no reaction when exposed to water or moist air for 24 hr. 

Trityl hexachloroantimonate polymerizes styrene only at relatively high concentrations (>10-2 M) [145]. This is apparently due to rapid formation of the covalent chloro adducts, which are relatively inactive in the presence of only a small amount of Lewis acid. Moreover, the SbCls generated in this reaction can add to styrene to form a 1,2-dichloroadduct and inactive SbCI3. In contrast, polymerization is fast with trityl hexaflu-oroantimonate [145], demonstrating the SbF6 counterion does not decompose to SbFs and F-terminated chains. 

Another method for enhancing the efficiency of initiation is to deactivate for growing species to a larger degree than the initiator. The use of sulfides as deactivators in the polymerization of vinyl ethers initiated by triflic acid and by trityl hexachloroantimonate are examples [37,38,135]. 

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