Stabilization of the Dinitrogen Analogue, 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 ^t Bu 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, reveals the PN multiple bond character, coordination to molybdenum induces a 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.