Phosphazenyl Phosphines: The Most Electron‐Rich Uncharged Phosphorus Brønsted and Lewis Bases

It was discovered that phosphazenyl phosphines (PAPs) can be stronger P‐superbases than the corresponding Schwesinger type phosphazene N‐superbases. A simple synthetic access to this class of PR₃ derivatives including their homologization is described. XRD structures, proton affinities (PA), and gas‐phase basicities (GB) as well as calculated and experimental pK values in THF are presented. In contrast to their N‐basic counterparts, PAPs are also privileged ligands in transition metal chemistry. In fact, they are currently the strongest uncharged P‐donors known, exceeding classical and more recently discovered ligands such as PtBu₃ and imidazolin‐2‐ylidenaminophosphines (IAPs) with respect to their low Tolman electronic parameters (TEPs) and large cone angles.