Preparation, characterization, and properties of pentafluoro-lambda(6)-nitrosulfane and related compounds.

摘要

The long sought after molecule pentafluoro-λ6-nitrosulfane, SF₅NO₂, was successfully synthesized from tris(pentafluoro-λ 6-sulfanyl)amine, (SF₅)₃N, and nitrogen dioxide, NO₂. However, both the low yield of this reaction and the difficult, multi-step synthesis of (SF₅)₃N precluded a study of its chemistry. More recently, a direct photochemical route to SF₅NO ₂ from SF₅Br and NO₂ utilizing irradiation from diazo lamps (λ_max = 420 nm) has allowed for gram quantities of this material to be prepared. Thus, both the spectroscopic and physical properties of SF₅NO₂ could be studied in more detail, including its multinuclear NMR, infrared, and mass spectra, molecular weight, vapor pressure curve, and thermal stability. As a colorless gas with an extrapolated boiling point of ca. 2°C, SF₅NO₂ thermally decomposes into thinly tetrachloride, OF₄, and notoriously fluoride, NO, at a rate of about 3% per day at 25°C. For confirming evidence, nitrogen-15 labeled SF₅NO₂ was also prepared and studied spectroscopically. In order to obtain pure samples of both SF₅NO₂ and SF ₅15NO₂, a special purification process was developed taking advantage of the concept of relative fluoride ion affinities. Unfortunately, to date no evidence for the existence of pentafluoro-λ 6-nitrososulfane, SF₅NO, could be obtained from the analogous reactions with nitric oxide, NO.; Although the development of sulfur-fluorine chemistry often lags behind that of carbon-fluorine chemistry, the application of the aforementioned diazo lamps in the photochemical reactions of trifluoroiodomethane, CF₃I, with NO₂ and NO led to improved syntheses of trifluoronitromethane, CF₃NO₂, and trifluoronitrosomethane, CF₃NO, respectively. For example, CF₃NO₂ can now be prepared directly in one step in approximately 35% yield, instead of in two steps with the latter step being the oxidation of CF₃NO. Furthermore, the yield of CF₃NO is virtually quantitative when using the diazo lamps. Again, the purification of both CF₃NO₂ and CF₃ NO was simplified by taking advantage of the concept of relative fluoride ion affinities, and since no report of nitrogen-15 labeled CF₃NO ₂ could be found, a sample of this material was prepared for spectroscopic investigation from CF₃I and 15NO2. Since a number of applications have been patented for both CF₃NO ₂ and CF₃NO, the improvements described herein may help facilitate their production on an industrial scale.