Reversible Stereoisomerization of 1,3-Diphosphetane Frameworks Revealed by a Single-Electron Redox Approach

The discovery of pyramidal inversion has continued to impact modern organic and organometallic chemistry. Sequential alkylation reactions of an N-heterocyclic carbene (NHC) ligated dicarbondiphosphide with RI (R = Me, Et, or iBu) and ZnMe give rise to the highly stereoselective synthesis of -1,3-diphosphetanes . - is conformationally favorable at room temperature, whereas inversion to - is observed at 110 °C. One-electron oxidation of - with Fc(BAr) (Fc = [Fe(CH)]; BAr = [B(3,5-(CF)CH))]) leads to the stereoselective formation of -1,3-diphosphetane radical cation salts (BAr), which can be reversibly transformed to - upon one-electron reduction. Salts (BAr) represent the first examples of 1,3-diphosphetane radical cations. These results provide a potential application of planar four-membered heterocycle-based building blocks for electrically fueled molecular switches.