Phosphorus(I) iodide: A versatile metathesis reagent for the synthesis of low oxidation state phosphorus compounds

An improved method for the synthesis of cyclic low oxidation state P cations is presented. The only byproducts of the reaction of phosphorus triiodide with chelating phosphines are readily removed, resulting in an easily accessible P-I reagent with an anion that can be readily replaced through salt metathesis chemistry. These P-I salts are surprisingly stable, even in O-2 and moisture, and the origin of this unusual stability is elucidated using density functional theory calculations.