The simplest iminophosphane HPNH and its photoisomerization to aminophosphinidene H2NP.

As a heavy analogue of dinitrogen, the diatomic phosphorus mononitride (PN) was the first detected phosphorus-containing compound in the interstellar medium. Hence, small molecules derived from PN including the simplest iminophosphane HPNH and isomeric aminophosphinidene H2NP with prototype phosphorus-nitrogen multiple bonds were proposed as candidate interstellar species possibly involving in the astrochemical network of PN. However, the existence and reactivity of HPNH and H2NP remain elusive. Here, we report the synthesis of the cis and trans conformers HPNH through high-vacuum flash pyrolysis of di-tert-butylphosphanamine in the gas phase. In addition to the photo-induced conformational interconversion in HPNH, its photoisomerization to H2NP in the singlet ground state has also been observed under the matrix-isolation conditions at 10 K. As a singlet phosphinidene, H2NP is very reactive as demonstrated by its photoreactions with CO and O2. The synthesis and characterization of the long sought-after [H2, N, P] isomers contribute to the fundamental knowledge about PN in main-group and interstellar chemistry.