Terrestrial Trapping of the Interstellar Gas, Phosphorus Nitride

The N2 analogue phosphorus nitride (PN) was the first phosphorus containing compound to be detected in the interstellar medium, however this thermodynamically unstable compound has a fleeting existence on Earth. Here, we show that reductive coupling of iron(IV) nitride and molybdenum(VI) phosphide complexes assembles PN as a bridging ligand in a structurally-characterized bimetallic complex. Reaction with C≡N^tBu releases the mononuclear complex [(N₃N)Mo-PN]⁻, N₃N = [(Me₃SiNCH₂CH₂)₃N]³⁻), which undergoes light-induced linkage isomerization to provide [(N₃N)Mo-NP]⁻, as revealed by photocrystallography. While structural and spectroscopic characterization, supported by electronic structure calculations reveal PN multiple bond character, coordination to molybdenum creates nucleophilic character at the terminal atom of the PN/NP ligands. Indeed, the linkage isomers can be trapped in solution by reaction with a Rh(I) electrophile.