Activating white phosphorus (P₄) to obtain other phosphorus species, such as phosphines, can be challenging and usually requires the use of hazardous chlorine. Some transition metals can activate P₄ in chlorine-free reactions to give phosphorus-containing metal complexes. Several main-group compounds can also react with P₄, however, the activation of white phosphorus with aluminium(I) species is not well explored.

Kota Koshino and Rei Kinjo, Nanyang Technological University, Singapore, have reacted a cyclic (alkyl)(amino)alumanyl anion (CAAAl, simplified structure pictured top left) with P₄. The CAAAl was prepared from an α,β-unsaturated imine and AlBr₃ in three steps. Adding P₄ to the CAAAl species in diethyl ether at room temperature gave a bis(alumanyl)phosphide (pictured above) in a yield of 36 % based on NMR data after 30 min.

To obtain crystals of the product that are suitable for X-ray crystallography, the team started from the dialane dimer that corresponds to the CAAAl, which was reduced using potassium graphite (KC₈) and then treated with P₄ and 12-crown-4 ether to give the desired bis(alumanyl)phosphide in 27 % isolated yield. The product has a bent structure with an Al–P–Al bond angle of ca. 107° and relatively short Al–P bonds. The work shows that white phosphorus can be fragmented into a P1 unit via activation by a CAAl species, achieving the direct conversion of an anionic Al species to an anionic P species.

• Fragmentation of White Phosphorus by a Cyclic (Alkyl)(Amino)Alumanyl Anion,
  Kota Koshino, Rei Kinjo,
  Organometallics 2020.
  https://doi.org/10.1021/acs.organomet.0c00444