Diphosphorus

Diphosphorus, P2, is the diatomic form of phosphorus. Unlike its nitrogen group neighbour 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.

Traditionally diphosphorus can be generated by heating white phosphorus at 1100 kelvins. The compound 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:


 * [[Image:Diphosphorus precursor.png|400px|Diphosphorus precursor]]

Heating this compound at 50 °C in 1,3-cyclohexadiene serving as a solvent and as a trapping reagent, expulses diphosphorus which reactive as it is forms a double Diels-Alder adduct and the niobium imido compound:


 * [[Image:DiphosphorusReaction.png|400px|Diphosphorus reaction]]

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