Unleashing phosphorus mononitride

The interstellar diatomic molecule, phosphorus mononitride (P≡N), is highly unstable under conditions typical on Earth, and its utility for constructing elusive P–N π-bonded motifs has remained uncertain. Here, we show how Na(OCP) transfers a P atom to an electrophilic osmium nitride complex to form a metal-bound P≡N ligand. Quantum chemical calculations and X-ray absorption spectroscopy unveil a cumulenic [Os^IV=N=P] electronic structure comprising orthogonal Os=N and N=P π-bonding. On reaction with elemental sulfur, the highly reduced P≡N ligand, formally [PN]^2–, forms a trigonal planar [NPS₂]^2– motif. Chlorination instead transforms the P≡N ligand to a bent [NPCl]^– group coordinated to Os^III (S = ½). [3 + 2] cycloaddition of this radical with azide forms an aromatic interpnictide, [PN₄]^–, that is inaccessible from the parent P≡N system. These findings provide a rare glimpse of the divergent reactivity of the alien P≡N molecule, paving the way to long-sought P–N multiple-bonded archetypes.