Sulfur difluoride

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). 

Bis(dialkylamino)sulfur difluorides, RjNSFaNRj, albeit less reactive than DAST, also substitute hydroxyl groups with fluorine [95, 97 /52]... 

Bis(dialkylamino)sulfur difluorides are often formed in reactions of SF4 with secondary amines. One example is given in Scheme 7.16. 

In the preparation of bis(trifluoromethyl)sulfur difluoride, explosions have occurred when chlorine mono- or tri-fluorides were treated with 2-3 mmol of the sulfide in absence of solvent. Because chlorine trifluoride is known to deprotonate solvents with formation of explosive carbene species, only fully halogenated solvents are suitable as diluents. 

Nitrile sulfides (37) have some, admittedly slight, structural affinity with the other nitrogen-sulfur reagents discussed in Section IV. They are unstable reactive intermediates that can be generated by the thermolysis of 1,3,4-oxathiazol-2-ones (38) or of 1,3,4-oxathiazoles (39).41 42 An alternative preparation is by the elimination of 2 moles of hydrogen fluoride from imini-sulfur difluorides (Scheme 5).43 Nitrile sulfides (37) are capable of undergoing... 

Bis(trifluoromethyl)-5-nitrobenzene, 2885 Bis(trifluoromethyl)sulfur difluoride, 0648 4-Bromocyclopentene, 1884 Bromoethane, 0846... 

The results (electrostatic-fit charges based on Hartree-Fock 6-3IG wavefunctions) are ambiguous. Relative to dimethylsulfide as a normal-valent standard , the sulfur in oxygen loses about half an electron, and the sulfur in dimethylsulfone loses 1.7 electrons. This would seem to suggest that dimethylsulfoxide is halfway to being a zwitterion, but that dimethylsulfone is most of the way. Charges on sulfur in sulfur tetrafluoride and sulfur hexafluoride (relative to sulfur difluoride) show more modest effects, in particular for the latter. Overall, it appears that hypervalent molecules possess significant ionic character. 

When treated with chlorine trifluoridc in CFC-12 at — 78 C, trifluoromethanesulfenyl chloride and bis(lrifluoromethyl) disulfide are transformed into trifluoromethylsulfur trifluoride (95%) and bis(trifluoromethyl)sulfur difluoride (90%). respectively.121... 

Sulfur tetrafluoride undergoes addition to perfluoroalkenes, e.g. 1 and 4, in the presence of cesium fluoride to give bis(perfluoroalkyl)sulfur difluorides and perfluoroalkylsulfur trifluorides.188,198 The ratio of the products is controlled by the reactant ratios. The role of cesium fluoride is ascribed to the formation of perfluorocarbanions which then subsequently attack sulfur tetrafluoride.188 Perfluoroalkyl disulfides, which are formed as side products, arise from the pyrolysis and disproportionation of bis(perfluoroalkyl)sulfur difluoridcs.189... 

Diphenylamine reacts with sulfur tetrafluoride in the presence of excess trimethylamine to give A,Ar -sulfinylbis(diphenylamine) (13) in low yield it is likely that bis(diphenylamine)sulfur difluoride is an intermediate.170... 

Many organic and inorganic cyanides, cyanates, isocyanates and thiocyanates react with sulfur tetrafluoride at elevated temperatures with the formation of iminosulfur difluorides. Thus, cyanogen bromide, sodium cyanide, and sodium thiocyanate give (trifluoromethyl)imino-sulfur difluoride (1) in 37 -70% yield.202... 

A solution of BnOH (1.1 g, 10 mmol) in anhyd CH2C12 (2 mL) was added slowly to a stirred solution of bis(dimethylamino)sulfur difluoride (1.0 g, 6.6 mmol) in CH2C12 (6 mL) at — 78 C. The mixture was allowed to warm to rt and was mixed with H20. The organic layer was separated, washed with H20 and aq NaHCOj (5%), and dried (MgS04). The solvent was removed by distillation to give the title compound yield 0.99 g (91%). 

Bis(trifluoromethyl) sulfoxide has been prepared1 previously by the direct fluorination of bis(trifluoromethyl) sulfide at —78°C. in hexafluoroethane followed by hydrolysis of the bis(trifluoro-methyl)sulfur difluoride (difluorobis(trifluoromethyl)sulfur). This method suffers because elemental fluorine must be used, and the yields are low. 

Oxidation of bis(trifluoromethyl) sulfide with commercially obtainable chlorine monofluoride in the absence of solvent yields bis(trifluoromethyl)sulfur difluoride in >90% yield.2,3 Pure bis-(trifluoromethyl)sulfur difluoride is resistant to hydrolysis and is stable in Pyrex glass at 25°C. for extended periods of time. Reaction of bis(trifluoromethyl)sulfur difluoride with anhydrous... 

At 25°C. bis(trifluoromethyl)sulfur difluoride is a colorless gas which condenses, on cooling, to a colorless liquid. A boiling point of... 

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