Reversible, photoinduced activation of P₄ by low-coordinate main group compounds.

Two unique systems based on low-coordinate main group elements that activate P-4 are shown to quantitatively release the phosphorus cage upon short exposure to UV light. This reactivity marks the first reversible reactivity of P-4, and the germanium system can be cycled 5times without appreciable loss in activity. Theoretical calculations reveal that the LUMO is antibonding with respect to the main group element-phosphorus bonds and bonding with respect to reforming the P-4 tetrahedron, providing a rationale for this unprecedented activity, and suggesting that the process is tunable based on the substituents.