Higher-valent sulfur fluorides

Sulfur tetrafluoride (SF4), a corrosive, moisture-sensitive gas, is commercially available. Industrially, it is most conveniently prepared via the following reaction  

Typical reaction conditions are shown below for an alcohol  

The mechanism of fluorination effected by SF4 or any of the dialkylaminosulfur trifluorides is illustrated below for a primary alcohol and DAST. The first step involves coordination of the alcohol to the tetravalent sulfur, followed by the departure of a fluoride leaving group  

The outgoing fluoride then comes back as a nucleophile, forming the alkyl fluoride product and kicking out an oxygen leaving group, as shown below  

Observe that the sulfur remains tetravalent at the end of the reaction thus, no redox has taken place. 

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