[en] A nitrogen-rich compound, ReN₈.xN₂, was synthesized by a direct reaction between rhenium and nitrogen at high pressure and high temperature in a laser-heated diamond anvil cell. Single-crystal X-ray diffraction revealed that the crystal structure, which is based on the ReN₈ framework, has rectangular-shaped channels that accommodate nitrogen molecules. Thus, despite a very high synthesis pressure, exceeding 100 GPa, ReN₈.xN₂ is an inclusion compound. The amount of trapped nitrogen (x) depends on the synthesis conditions. The polydiazenediyl chains [-N=N-]_∞ that constitute the framework have not been previously observed in any compound. Ab initio calculations on ReN₈.xN₂ provide strong support for the experimental results and conclusions. (copyright 2018 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

[en] Two novel yttrium nitrides, YN${}_6$ and Y${}_2$N${}_{11}$, were synthesized by direct reaction between yttrium and nitrogen at 100 GPa and 3000 K in a laser-heated diamond anvil cell. High-pressure synchrotron single-crystal X-ray diffraction revealed that the crystal structures of YN${}_6$ and Y${}_2$N${}_{11}$ feature a unique organization of nitrogen atoms---a previously unknown anionic N${}_{18}$ macrocycle and a polynitrogen double helix, respectively. Density functional theory calculations, confirming the dynamical stability of the YN${}_6$ and Y${}_2$N${}_{11}$ compounds, show an anion-driven metallicity, explaining the unusual bond orders in the polynitrogen units. As the charge state of the polynitrogen double helix in Y${}_2$N${}_{11}$ is different from that previously found in Hf${}_2$N${}_{11}$ and because N${}_{18}$ macrocycles have never been predicted or observed, their discovery significantly extends the chemistry of polynitrides. (© 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH)