Oxidative Fluorination of Selenium and Tellurium Compounds using a Thermally Stable Phosphonium SF(5) (−) Salt Accessible from SF(6)

Fluorinated group 16 moieties are attractive building blocks in synthetic chemistry but only few synthetic methods are available to prepare them. Herein, we report a new oxidative fluorination reagent capable of stabilizing reactive fluorinated anions. It consists of an SF(5) (−) anion and a chemically inert phosphonium cation and is exceptionally thermally stable. Accordingly, it was used to generate the SeF(5) (−) and TeF(5) (−) anions from the elemental chalcogens and to prepare the unknown tetrafluoro(phenyl)‐λ(5)‐selenate PhSeF(4) (−) and ‐tellurate PhTeF(4) (−) from the corresponding diphenyl dichalcogenides. In addition, we show that further derivatization of [PhTeF(4)](−) by oxidation to trans‐PhTeF(4)O(−) and subsequent alkylation gives access to a new class of trans‐(alkoxy)(phenyl)tetrafluoro‐λ(6)‐tellanes (trans‐PhTeF(4)OR), thus providing an approach to introduce the functional group into organic molecules.