The diphosphorus allotrope (P2) can be obtained normally only under extreme conditions (for example, from P4 at 1100 kelvin). Nevertheless, some advancements were obtained in generating the diatomic molecule in homogenous solution, under normal conditions with the use by some transition metal complexes (based on for example tungsten and niobium).
Diphosphorus is the gaseous form of phosphorus, and the thermodynamically stable form above 1200 °C and until 2000 °C. The dissociation of tetraphosphorus (P4) begins at lower temperature: the percentage of P2 at 800 °C is ≈ 1%. At temperatures above about 2000 °C, the diphosphorus molecule begins to dissociate into atomic phosphorus.
Read more about this topic: Allotropes Of Phosphorus