Sulfur fluoride

The known binary compounds of sulfur and fluorine range in character from ephemeral to rock-like and provide excellent examples of the influence of electronic and stmctural factors on chemical reactivity. These marked differences are also reflected in the diversified technological utiUty. 

Sulfur hexafluoride [2551-62-4] 6 molecular weight 146.07, is a colorless, odorless, tasteless gas. It is not flammable and not particularly reactive. Its high chemical stabiUty and excellent electrical characteristics have led to widespread use in various kinds of electrical and electronic equipment such as circuit breakers, capacitors, transformers, microwave components, etc (see Electronic materials). Other properties of the gas have led to limited usage in a variety of unique appHcations ranging from medical appHcations to space research. 

Sulfur hexafluoride was first prepared in 1902 (1). The discovery in 1937 that its dielectric strength is much higher than that of air (2) led to its use as an insulating material for cables, capacitors (3), and transformers (4) (see Insulation,electric). Sulfur hexafluoride has been commercially available as AccuDri, SF (AUiedSignal Inc.) since 1948. It is also produced by Air Products and Chemicals in the United States and by others in Germany, Italy, Japan, and Russia. 

Properties. Sulfur hexafluoride is a good dielectric because a high gas density can be maintained at low temperatures. Properties are given in 

Kirk-Othmer Encyclopedia of Chemical Technology (4th Edition) 

The seven known sulfur fluorides are quite different from the other halides of sulfur in their stability, reactivity and to some extent even in their stoichiometries it is therefore convenient to 

The regular octahedral structure of SFg and the related structure of S2F]q (Fig. 15.20) call for little comment except to note the staggered (D4d) arrangement of the two sets of Feq in S2F10 and the unusually long S-S distance, both features presumably reflecting interatomic repulsion between the F atoms. SFg is also of 

Some physical properties of the more stable sulfur fluorides are in Table 15.13. All are colourless gases or volatile liquids at room temperature. SFg sublimes at -63.8° (1 atm) and can only be melted under pressure (—50.8°). It is notable both for its extreme thermal and chemical stability (see below), and also for having a higher gas density than any other substance that boils below room temperature (5.107 times as dense as air). 

SSF2 can be heated to 250° but is, in fact, thermodynamically unstable with respect to disproportionation, being immediately transformed to SF4 in the presence of acid catalysts such as BF3 or HF  

Both S2F2 and SSF2 are rapidly hydrolysed by pure water to give Sg, HF and a mixture of polythionic acids H2S Oe (n 4-6), e.g.  

Minkwitz, R. Krause, H. HArtner and W. Sawodny, Z. anorg. allg. Chem. 593, 137-46 (1991). 

S-F bond. The structure of the resulting molecule F3SSF is, in a sense, intermediate between those of S2F2 and SF4, being based on a trigonal bipyramid with the equatorial F atom replaced by an SF group. The fact that the F nmr spectrum at —100° shows four distinct F resonances indicates that the 2 axial F atoms are non-equivalent, implying restricted rotation about the S-S bond. 

All of the different types of sulfur fluorides are discussed in this section. The SF5 substituent is discussed in detail in the following section. 

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FLUORINECOMPOUNDS,INORGANIC - SULFUR - SULFUR FLUORIDES] (Vol 11) PA. See Polyamide, amorphous. 

Nonmeta.ls, Sulfur reacts with fluorine to yield the remarkably stable sulfur hexafluoride, SF. Operating conditions must be controlled because a mixture of the lower fluorides such as disulfur difluoride [13709-35-8] 2 2 disulfur decafluoride [5714-22-7] 2 10 sulfur tetrafluoride [7783-60-0] SF4, may also be formed. When this reaction is carried out between 310 and 340°C, SF is primarily obtained and essentially no SF and only trace amounts of lower fluorides. Below 300°C, and preferably at ca 275°C, SF is the primary product. At 450—500°C, a mixture comprising ca 50% SF and the lower sulfur fluorides is formed (see Fluorine compounds, inorganic-sulfur). 

Other Sulfur Fluorides Although eight other binary sulfur fluorides have been synthesized and characterized, proof of the existence of several members of this group was dependent on modem instmmental methods of analysis because of extreme instabiUty. SF and S2F2Q are stable, however, the latter is noted for its extreme toxicity. AH sulfur fluorides other than SF must be considered extremely toxic. 

Table 15.13 Physical properties of some sulfur fluorides...

Fluor-jod, n. iodine fluoride, -kalium, n. potassium fluoride, -kalzium, n. calcium fluoride, -kiesel, m. silicon fluoride, -kie-selsaure,/. fluosilicic acid, -kohlenstoff, m. carbon fluoride, -lithium, n. lithium fluoride. -metall, n. metallic fluoride, -natrium, n. sodium fluoride, -phosphat, n. fluophosphate. -phosphor, m. phosphorus fluoride, -salz, n. fluoride, -schwefel, m. sulfur fluoride, -selen, n. selenium fluoride, -silber, n. silver fluoride, -silikat, n. fluo-silicate. -silizium, n. silicon fluoride, -sili-ziumverbindung, /. fluosilicate. -tantal-sMure, /. fluotantalic acid, -tellur, n. tellurium fluoride, -titan, n. titanium fluoride, -toluol, n. fluorotoluene, fluotoluene. 

There are a number of other methods to prepare crude sulfane oils, e.g., from hquid H2S and elemental chlorine or bromine [10] or by reaction of H2S with sulfur fluorides [10] or sulfur chlorides [20] but these processes are of httle practical importance. 

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