|Jmol-3D images||Image 1|
|Molar mass||61.95 g mol−1|
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Diphosphorus, P2, is the diatomic form of phosphorus. Unlike its nitrogen group neighbor nitrogen, which forms a stable N2 molecule with a nitrogen to nitrogen triple bond, phosphorus prefers a tetrahedral form P4 because P-P pi-bonds are high in energy. Diphosphorus is, therefore, very reactive with a bond-dissociation energy (117 kcal/mol or 490 kJ/mol) half that of dinitrogen. The bond distance has been measured at 1.8934 Å.
Diphosphorus has been generated by heating white phosphorus at 1100 kelvins. Nevertheless, some advancements have been obtained in generating the diatomic molecule in homogeneous solution, under normal conditions with the use by some transition metal complexes (based on, for example, tungsten and niobium).
The molecule attracted attention in 2006, when a new method for its synthesis at milder temperatures emerged.
This method is a variation on nitrogen expulsion in azides with formation of a nitrene. The synthesis of the diphosphorus precursor consists of reacting a terminal niobium phosphide with a chloroiminophosphane:
Heating this compound at 50 °C in 1,3-cyclohexadiene serving as a solvent and as a trapping reagent expulses diphosphorus, which is reactive, as it is forms a double Diels-Alder adduct and the niobium imido compound:
P2 has been suggested to form as an intermediate in the photolysis of P4  and in the presence of 2,3-dimethylbutadiene the diphosphane is again formed  To date, no direct evidence of P2 formation via P4 photolysis exists.
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