Fluorosulfates

Recently, the concept of inductive effect have been applied to replace (P04) for (804) in polyanionic cathode materials [35, 36, 93-119]. Table 8.3 summarizes the structural properties of some fluorosulfate compoxmds. The fluorosulfates LLMSO4F constitute a wide family showing a good mix of properties, especially, both electrochemical and safety issues. However, we notice that the electroactive compounds appeared only in 2010 after the synthesis of newest member of the tavorite family LiFe (S04)F [36]. For instance, a simple substitution in Nasicon Li cM3(X04)3 networks increases the redox potential by 800 mV independently of the 2 d transition-metal ion [2]. Recent review by Rousse and Tarascon [119] deals with the crystal chemistry and structural-electrochemical relationship of new fluorosulfate polyanionic LiMS04p electrode materials. The lithiated fluorosulfates present an interesting family from the view point of crystal chemistry with the three main types of structure that depend on the nature of the transition-metal ion  

The redox potential of the fluorosulfates LiMS04F (M = Co, Ni, Mn) are expected to exhibit redox potentials of 4.25, 4.95, and 5.25 V, respectively. Barpanda et al. [100] succeeded in preparing the Li(Fei M , )S04F solid solutions only 

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Hexafluoroarsenic acid [17068-85-8] can be prepared by the reaction of arsenic acid with hydrofluoric acid or calcium fluorosulfate (29) and with alkaH or alkaline-earth metal fluorides or fluorosulfonates (18). The hexafluoroarsenates can be prepared directly from arsenates and hydrofluoric acid, or by neutrali2ation of HAsF. The reaction of 48% HF with potassium dihydrogen arsenate(V), KH2ASO4, gives potassium hydroxypentafluoroarsenate(V)... 

Fluorosulfuric acid [7789-21-17, HSO F, is a colodess-to-light yellow liquid that fumes strongly in moist air and has a sharp odor. It may be regarded as a mixed anhydride of sulfuric and hydrofluoric acids. Fluorosulfuric acid was first identified and characterized in 1892 (1). It is a strong acid and is employed as a catalyst and chemical reagent in a number of chemical processes, such as alkylation (qv), acylation, polymerization, sulfonation, isomerization, and production of organic fluorosulfates (see Friedel-CRAFTSreactions). 

The extent of the initial hydrolysis depends on temperature and how the water is added. Hydrolysis is reduced at slower addition rates and lower temperatures. The hydrolysis subsequent to the initial fast reaction is slow, presumably because part of the acid is converted to fluorosulfate ions which hydrolyze slowly even at elevated temperatures. The hydrolysis in basic solution has also been studied (17). Under controlled conditions, hydrates of HSO F containing one, two, and four molecules of water have been observed (18,19). 

Precipitated (hydrated) siUca reacts vigorously with fluorosulfuric acid to give siUcon tetrafluoride [7783-61-1] (21), but glass (qv) is not attacked in the absence of moisture (20). Alkali and alkaline-earth metal chlorides are readily converted to fluorosulfates by treatment with fluorosulfuric acid (7,13,22,23). 

Fluorosulfuric acid may be used to prepare diazonium fluorosulfates, ArN SO.F (44), which decompose on heating to give aryl (Ar) fluorosulfates (36,45). Aryl fluorosulfates are also obtained from arylsulfonyl chlorides and fluorosulfuric acid (35). Alkyl and other organofluorosulfates form during electrolysis of fluorosulfuric acid in the presence of organic species (46,47). 

Preparation and Manufacture. Fluorosulfuric acid, first prepared by combining anhydrous HF and cooled, anhydrous SO in a platinum container (1), has also been prepared from ionic fluorides or fluorosulfates and sulfuric acid (20,48). The reaction of chlorosulfuric acid (qv) with ionic fluorides also gives fluorosulfuric acid (49). 

Derivatives. The nonmetaHic inorganic derivatives of fluorosulfuric acid are generally made indirectly, although complex fluorosulfates of the Group 15 (V) elements and of xenon can be made directly (85,86), as can the NO" and NO" 2 salts (26,27). 

Peroxydisulfuryl difluoride [13709-32-5] FSO2OOSO2F, prepared from fluorine and SO (87), is a ready source of fluorosulfate radicals, FSO2O , (88) which react with many substances to form stable fluorosulfates (89,90). By using the route... 

Ammonium fluorosulfate is produced from ammonium fluoride by reaction with sulfur trioxide, oleum, or potassium pyrosulfate, 1 2820 (48). Solutions of ammonium fluorosulfate show Htfle evidence of hydrolysis and the salt may be recrystallized from hot water. Ammonium fluorosulfate absorbs anhydrous ammonia to form a series of Hquid amines that contain 2.5—6 moles of ammonia per mole of salt (77). 

Sodium fluorosulfate may be prepared by the action of fluorosulfuric acid on powdered, ignited sodium chloride (13) or of sulfur trioxide on sodium fluoride (48). In general, the alkah metal fluorosulfates may be prepared from the ammonium salt by evaporating a solution containing that salt and an alkah metal hydroxide (77). The solubiUties of some Group 1 and 2 fluorosulfates in fluorosulfuric acid have been deterrnined (93). 

The monofluoromethylene group and difluoromethyl group m 1H perfluoro-alkanes and -cycloalkanes are oxidized at the C-H bond to perfluoroalkyl and perfluorocycloalkyl fluorosulfates by anodic oxidation m fluorosulfonic acid [J, 4] Two modifications of the method are used ox idation by fluorosulfonyl peroxide generated pnor to the reaction [J] (equation 2A) and direct electrolysis m the acid [i, 4] (equabons 2B and 3)... 

Hexafluoropropene is converted to its 1,2-epoxide in 55% yield by bubbling through a solution of chromium tnoxide in fluorosulfonic acid [8], the analogous reaction with a mixture of chromium trioxide and dichromium tnoxide gives pentafluoroacetonyl fluorosulfate [.5] (equation 6)... 

Nitronium fluorosulfate in fluorosulfonic acid adds electrophilically across the double bond offluoroolefins in a nonspecific manner. Tnfluorochloroethylene reacts accordingly with nitronium fluorosulfate to give a 2.1 mixture of regio-isomers [7] (equation 7). Under these reaction conditions perfluoropropylene is unreactive even after extended heating at 80 C 2-Nitroperfluoropropyl fluorosulfate is obtained on treatment of the perfluoropropylene with nitronium fluorosulfate in antimony pentafluoride [5] (equation 8). 

Perfluoroallyl fluorosulfate is prepared by the treatment oiperfluoropropene with sulfur tnoxide m the presence of boron catalysts [2, 3, 4, 5, 6, 7] (equation 2) Perfluoroisopropyl allyl ether reacts similarly to give 58% polyfluoroallyl fluorosulfate in a cis/trans ratio of 6 4 [S] Sultones are the exclusive products without catalyst. Polyfluoroolefins such as 2-hydropentafluoropropylene [9], (2,3-dichloropropyl)tri-fluoroethylene [70], perfluoropropene [2, i], perfluoroisopropyl alkenyl ethers [S], and acyclic polyfluoroallyl ethers [77] undergo sulfur trioxidation to regioselectively produce the corresponding P-sultones in high yield... 

Insertion of sulfur trioxide mioperfluorotoluenes occurs on extended heating with sulfur trioxide to provide perfluorobenzyl fluorosulfates [18,19] (equation 8)... 

A peculiar reaction of perfluoroalkyl halides with chlorine fluorosulfate yields perfluoroalkyl fluorosulfales [iS (equation 17)... 

Polyfluoroalkyl fluorosulfates react with substituted hydrazines to give the corresponding polyfluorocarboxylic hydrazides [90] (equation 78)... 

Unlike its analogue FCIO3 it forms adducts with BF3 and AsFs, possibly by F" donation to give [I03]+[BF4 ] and [I03]+[AsF6]", though the structures have not yet been determined. Alternatively, the coordination number of the central I atom might be increased. SO3 reduces FIO3 to iodyl fluorosulfate ... 

Table 17.27 Some physical properties of halogen fluorosulfates ...

Marteau and G.H. Cady, The Reaction of Peroxydisulfuryl Difluoride with Anhydrides of Certain Perhalocarboxylic Acids to Form Per-haloacyl Fluorosulfates , Univ Wash, Seattle,... 

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