Catenation is much more common in phosphorous compounds than in nitrogen
compounds because of the relative weakness of the N−N single bond as compared
to the P−P single bond. The self-linking tendency of nitrogen is restricted to only one atom by the formation of a triple bond whereas it extends for phosphorous due to its larger size. Since nitrogen atom is smaller, there is more repulsion of electron density around two nitrogen atoms, thereby weakening the N−N single bond.