Generation of a π‐Bonded Isomer of [P4]4− by Aluminyl Reduction of White Phosphorus and its Ammonolysis to PH3

By employing the highly reducing aluminyl complex [K{(NON)Al}]2 (NON=4,5‐bis(2,6‐diisopropylanilido)‐2,7‐di‐tert‐butyl‐9,9‐dimethylxanthene), we demonstrate the controlled formation of P42− and P44− complexes from white phosphorus, and chemically reversible inter‐conversion between them. The tetra‐anion features a unique planar π‐bonded structure, with the incorporation of the K+ cations implicit in the use of the anionic nucleophile offering additional stabilization of the unsaturated isomer of the P44−fragment. This complex is extremely reactive, acting as a source of P3−: exposure to ammonia leads to the release of phosphine (PH3) under mild conditions (room temperature and pressure), which contrast with those necessitated for the direct combination of P4 and NH3 (>5 kbar and >250 °C). The reduction of white phosphorus by an aluminum(I) anion is explored. The four‐electron reduction product serves as a means of phosphine gas production on exposure to ammonia.