[en] Laser heating of rhenium in a diamond anvil cell to 3000±300 K at about 200 GPa results in formation of two previously unknown rhenium carbides, hexagonal WC-type structured ReC and orthorhombic $TiS{i}_2$-type structured $Re{C}_2$. The shortest C-C distances [1.758(3) Å at 219(5) GPa and 1.850(4) Å at 180(7) GPa] found in honeycomb-like carbon nets in the structure of $Re{C}_2$ are quite unusual. The Re-C solid solution formed at multimegabar pressure has the carbon content of ≈ 20 at%. (© 2020 The Authors. Published by Wiley‐VCH Verlag GmbH and Co. KGaA.)

[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)

[en] A series of isostructural Ln${}_3$O${}_2$(CN${}_3$) (Ln=La, Eu, Gd, Tb, Ho, Yb) oxoguanidinates was synthesized under high-pressure (25-54 GPa) high-temperature (2000-3000 K) conditions in laser-heated diamond anvil cells. The crystal structure of this novel class of compounds was determined via synchrotron single-crystal X-ray diffraction (SCXRD) as well as corroborated by X-ray absorption near edge structure (XANES) measurements and density functional theory (DFT) calculations. The Ln${}_3$O${}_2$(CN${}_3$) solids are composed of the hitherto unknown CN${}_3$${}^{5-<!--\; ???\; -->}$ guanidinate anion---deprotonated guanidine. Changes in unit cell volumes and compressibility of Ln${}_3$O${}_2$(CN${}_3$) (Ln=La, Eu, Gd, Tb, Ho, Yb) compounds are found to be dictated by the lanthanide contraction phenomenon. Decompression experiments show that Ln${}_3$O${}_2$(CN${}_3$) compounds are recoverable to ambient conditions. The stabilization of the CN${}_3$${}^{5-<!--\; ???\; -->}$ guanidinate anion at ambient conditions provides new opportunities in inorganic and organic synthetic chemistry. (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH)

[en] Polynitrides are intrinsically thermodynamically unstable at ambient conditions and require peculiar synthetic approaches. Now, a one‐step synthesis of metal–inorganic frameworks Hf${}_4$N${}_{20}$⋅N${}_2$, WN${}_8$⋅N${}_2$, and Os${}_5$N${}_{28}$⋅3 N${}_2$ via direct reactions between elements in a diamond anvil cell at pressures exceeding 100 GPa is reported. The porous frameworks (Hf${}_4$N${}_{20}$, WN${}_8$, and Os${}_5$N${}_{28}$) are built from transition‐metal atoms linked either by polymeric polydiazenediyl (polyacetylene‐like) nitrogen chains or through dinitrogen units. Triply bound dinitrogen molecules occupy channels of these frameworks. Owing to conjugated polydiazenediyl chains, these compounds exhibit metallic properties. The high‐pressure reaction between Hf and N${}_2$ also leads to a non‐centrosymmetric polynitride Hf2N11 that features double‐helix catena‐poly[tetraz‐1‐ene‐1,4‐diyl] nitrogen chains [−N−N−N=N−]${}_{\mathrm{\infty <!--\; ???\; -->}}$. (© 2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)