Diazophosphane HPN 2 .

Diazophosphane HPN 2 , a heavy analogue of hydrazoic acid (HN 3 ), has been synthesized at low temperature (10 K) through photolytic reactions of molecular nitrogen (N 2 ) with phosphine (PH 3 ) and phosphaketene (HPCO) under irradiations at 193 and 365 nm, respectively. The characterization of HPN 2 and its isotopologues DPN 2 and HP 15 N 2 by matrix-isolation IR and UV-vis spectroscopy is supported by quantum chemical calculations at the CCSD(T)-F12a/cc-pVTZ-F12 level of theory. Upon irradiation at 266 nm, the P-N bond in HPN 2 breaks, whereas its photolysis at 193 nm generates the elusive phosphinyl radical • PN 2 .