Sulfur Tetrafluoride SF

Sulfur Tetrafluoride and Aromatic Carboxylic Acids. Ben2otrifluorides also are prepared from aromatic carboxyhc acids and their derivatives with sulfur tetrafluoride (SF (106,107). Hydrogen fluoride is frequently used as a catalyst. Two equivalents of sulfur tetrafluoride are required ... 

Sulfur tetrafluoride (SF or diethylaminosulfur trifluoride (EtjNSFj) are useful reagents for converting alcohols to fluorides. Diethylaminosulfur trifluoride will also react with aldehydes and ketones to form difluorides. 

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). 

Preparation. In the laboratory, sulfur tetrafluoride is made by combining SCI2 and NaF suspended in acetonitrile at ca 77°C (106). For commercial production, SF is made by direct combination of sulfur with elemental fluorine (107). Commercial appHcations of SF are limited. It is available from Air Products and Chemicals. 

Toxicity. Sulfur tetrafluoride has an inhalation toxicity comparable to phosgene. The current OSHA standard maximum allowable concentration for human exposure in air is 0.4 mg/m (TWA) (54). On exposure to moisture, eg, on the surface of skin, sulfur tetrafluoride Hberates hydrofluoric acid and care must be taken to avoid bums. One case of accidental exposure of electrical workers to decomposed SF gas containing SF has been cited (108). 

Sulfur tetrafluoride [7783-60-0] SF, replaces halogen in haloalkanes, haloalkenes, and aryl chlorides, but is only effective (even at elevated temperatures) in the presence of a Lewis acid catalyst. The reagent is most often used in the replacement of carbonyl oxygen with fluorine (15,16). Aldehydes and ketones react readily, particularly if no alpha-hydrogen atoms are present (eg, benzal fluoride [455-31-2] from benzaldehyde), but acids, esters, acid chlorides, and anhydrides are very sluggish. However, these reactions can be catalyzed by Lewis acids (HP, BF, etc). 

Sulfur tetrafluoride is available from Air Products and Chemicals, Inc. or Matheson Gas Products. Commercial SF was used without purification. 

The most intense bands, as well as overtone bands at 1744 and 1281 cm"1, are used as purity probes for sulfur tetrafluoride.9 The mass spectrum of sulfur tetrafluoride shows a weak molecular peak and strong fragmentation peaks corresponding to SF/, SF2+, SF+ and F+ ions.10... 

Primary amines react with sulfur tetrafluoride to form an N=S bond. Ammonia reacts with sulfur tetrafluoride at ambient temperature in a flow system to form an unstable gas, thiazyl fluoride (N =SF. 20 Vo).193 194 The reaction with melhylamine conducted at low temperatures affords methyliminosulfur difluoride (1) with excess methylaminc, bis(melhylimino)sulfur is formed as the main product.195,196... 

Selenium hexafluoride, SeFg, the only clearly defined hexahalide, is formed by reaction of fluorine with molten selenium, It is more reactive than the corresponding sulfur compound, SFs, undergoing slow hydrolysis. Selenium forms tetrahalides with fluorine, chlorine, and bromine, and dihalides with chlorine and bromine. However, other halides can be found in complexes, e.g,. treatment of the pyridine complex of SeF/i in ether solution with HBr yields (py)2SeBrc Selenium tetrafluoride also forms complexes with metal fluorides, giving MSeF complexes with the alkali metals. 

Sulfur tetrafluoride Fluorides from boric acid esters s. 18,611 SF, (RO)gB 3RF... 

Disulfur decafluoride does not react rapidly with water, mercury, copper, or platinum at ambient temperatures. There is evidence that it slowly decomposes on various surfaces in the presence of water when stored in the vapor state (118). It is decomposed by molten KOH to give a mixture of potassium compounds of sulfur and fluorine. The gas reacts vigorously with many other metals and siUca at red heat (114). At ca 156°C it combines with CI2 or Br2 to form SF Cl or SF Br (119,120). At ca 200°C, S2F2Q is almost completely thermally decomposed into the hexa- and tetrafluoride (121). 

Difluoromonosulfane and Difluorodisulfane Difluoride. Difluoromonosulfane [13814-25-0] (sulfur difluoride), SF2, and its dimer, disulfane tetrafluoride [27245-05-2] SF SF, are both extremely unstable compounds which have only a fleeting existence except under rigorously controlled laboratory conditions. These compounds may be prepared by passing SCl vapor over HgF2 at 150°C (131). Electronic and nmr examinations of SF2 have been reported (132,133). 

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