Imidodisulfuryl Fluoride

This purification process is particularly important if the imidodisulfuryl fluoride is to be used in the preparation of fluoroimidodisulfuryl fluoride since the fluorination of imido-disulfuryl fluoride which contains small amounts of fluorosulfuric acid does not occur under the conditions to be described. However, if imidodisulfuryl fluoride is to be converted to one of the alkali metal salts, this purification step is not necessary. 

Imidodisulfuryl fluoride is a colorless liquid, b.p. 170°, m.p. 17°. It behaves as a weak acid in water, in w-hich it is stable, and undergoes slow hydrolysis in alkaline solution. The infrared spectrum of imidodisulfuryl fluoride obtained using silver chloride plates (it reacts with sodium chloride) contains bands at 3311(m), 1471(vs), 1337(w), 1248(w), 1217(vs), 923(s), 893(m), and 832(s) cm. . The n.m.r. spectrum of imidodisulfuryl fluoride consists of a single band at —58.5 p.p.m. (from CC1 F), and the proton spectrum consists of a single band at —8.60 p.p.m. (from TMS). 

sample of imidodisulfurji fluoride is placed in a 300 ml. round-bottomed flask and cooled to —78°. Then 50 ml. of ice water is slowiy added, and the mixture is allow ed to warm to ambient temperature. The solution is just neutralized with cesium carbonate (approximately 7.5 g.). The neutralization can be followed with pH paper. The mixture is evaporated to 

Cesium imidodisulfuryl fluoride is a white crystalline solid with a remarkably low melting point for an alkali metal salt, m.p. 115-117°. Differential thermal anal3rsis shows that it is stable up to 300°. Cesium imidodisulfuryl fluoride behaves as a 1 1 electrolyte in nitromethane. The infrared spectrum of cesium imidodisulfuryl fluoride contains bands at 1940(vw), 1836(vw), 1379(vs), 1222(w), 1179(vs), llOl(s), 843(s), 820(sh), 763(vs), and 729(vs) cm.  

---

IMIDODISULFXJRYL FLUORIDE, CESIUM IMIDODISULFURYL FLUORIDE, AND FLUOROIMIDODISULFURYL FLUORIDE... 

Imidodisulfuryl fluoride is a useful intermediate for the preparation of a number of compounds containing the N(S02F)2 group. It was first prepared by the reaction of fluorosulfjiric acid with urea. This method gives inconsistent yields and is sometimes difficult to control. A more convenient procedure involves a halide exchange reaction between ar8enic(III) fluoride and imidodisulfuryl chloride. 

Neutralization of imidodisulfuryl fluoride with the alkali-metal carbonates results in the formation of the corresponding alkali metal imidodisulfuryl fluoride salts. Fluorination of imidodisulftu yl fluoride at ambient temperature produces fluoro-imidodisulfuryl fluoride in high yield. ... 

Available from Alfa Inorganics, 8 Congress St., Beverly, Maas. tThe yield of imidodisulfuryl fluoride will decrease with additional time, because NaCl slowly reacts with. it. Therefore care should be taken to minimize the formation of FSOiH. 

Imidodisulfuryl fluoride,f 18.5 g. (0.102 mole), is loaded into a Pyrex U-tube containing a small magnetic stirring bar. The U-tube is attached to the fractionation train on the vacuum line, and the train is flushed with helium. The two adjacent U-tubes are cooled to —78°, and the last U-tube is cooled to —196°. The two —78° traps should be packed with Pyrex helices to ensure efficient trapping. The fluorine tank is opened, and the concentration of fluorine is adjusted to approximately 30%. The helium-diluted fluorine is passed over the surface of the imidodisulfuryl fluoride at ambient temperature and at a flow rate of 150-175 ml./minute for appro.ximately 2 hours or until most of the imidodisulfuryl fluoride has disappeared from the U-tube. After the fluorination is finished, the system is flushed for 15 minutes with helium and then evacuated. The contents of the two —78° traps [crude FN(SOiF)2] are combined. Final purification is achieved by slow fractionation through U-tubes maintained at —33° (bromobenzene slush) and —78°. The former trap retains approximately 1 g. of imidodisulfuryl fluoride the —78° trap collects 15.3 g. (75% yield) of fluoroimido-disulfuryl fluoride. Anal. Calcd. for FN(SO F)2 N, 7.03 S, 32.3 F, 28.6. Found N, 7.11 S, 32.7 F, 28.8. 

Minnesota Mining and Manufacturing Company, Minneapolis, Minn, t Imidodisulfuryl fluoride should be freed from FSOjH and handled in a moisture-free atmosphere. The yield is diminished by the presence of FSO>H. 

---