What is "diphosphorus"

n. (context chemistry in combination English) two atoms of phosphorus in a compound

Diphosphorus is an inorganic chemical with the chemical formula . Unlike its nitrogen group neighbor nitrogen, which forms a stable N molecule with a nitrogen to nitrogen triple bond, phosphorus prefers a tetrahedral form P 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 of 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:

The same imido compound also forms when the thermolysis is performed in toluene but then the fate of diphosphorus is unknown.

P has been suggested to form as an intermediate in the photolysis of P and in the presence of 2,3-dimethyl-1,3-butadiene the diphosphane is again formed. To date, no direct evidence of P formation via P photolysis exists.

The generation of diphosphorus from a diphosphorus bisanthracene adduct has been reported. The synthesis of a stabilized HP cation has been reported