Redox‐Triggered Reversible Interconversion of a Monocyclic and a Bicyclic Phosphorus Heterocycle

Abstract

AbstractMolecules which change their structures significantly and reversibly upon an oxidation or reduction process have potential as future components of smart materials. A prerequisite for such an application is that the molecules should undergo the redox‐coupled transformation within a reasonable electrochemical window and lock into stable redox states. Sodium phosphaethynolate reacts with two equivalents of dicyclohexylcarbodiimide (DCC) to yield an anionic, imino‐functionalized 1,3,5‐diazaphosphinane [3 a]−. The oxidation of this anion with elemental iodine causes an intramolecular rearrangement reaction to give a bicyclic 1,3,2‐diazaphospholenium cation [6]+. This umpolung of electronic properties from non‐aromatic to highly aromatic is reversible, and the cation [6]+ is reduced with elemental magnesium to reform the 1,3,5‐diazaphosphinanide anion [3 a]−. Theoretical calculations suggest that phosphinidene species are involved in the rearrangement processes.