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.