Stabilization of the [C <sub>2</sub> N <sub>5</sub> ] <sup>7–</sup> Anion in Recoverable High-Pressure Eu <sub>4</sub> Fe <sub>0.864(6)</sub> (C <sub>2</sub> N <sub>5</sub> ) <sub>2</sub> Pyronitridocarbonate
Synthesis at extreme conditions enables access to nitrogen-rich carbon-nitrogen anions that cannot be obtained at ambient conditions. Here, through a direct reaction between Eu(N<sub>3</sub>)<sub>2</sub> and EuC<sub>2</sub> with Fe in a laser-heated diamond anvil cell (DAC) at 50(3) GPa, we synthesized the first inorganic hydrogen-free pyronitridocarbonate, Eu<sub>4</sub>Fe<sub><i>x</i></sub>(C<sub>2</sub>N<sub>5</sub>)<sub>2</sub>, <i>x</i> = 0.864(6), featuring novel highly charged [C<sub>2</sub>N<sub>5</sub>]<sup>7-</sup> anions, along with the first stoichiometric oxygen-free rare-earth metal guanidinate Eu<sub>5</sub>(CN<sub>3</sub>)<sub>3</sub>. The crystal structures of both compounds were determined via synchrotron single-crystal X-ray diffraction (SCXRD) and fully corroborated by density functional theory (DFT) calculations. Eu<sub>4</sub>Fe<sub><i>x</i></sub>(C<sub>2</sub>N<sub>5</sub>)<sub>2</sub> was found to be recoverable at pressures close to ambient. Keeping the sample at ambient conditions for 1 day leads to splitting of half of the [C<sub>2</sub>N<sub>5</sub>]<sup>7-</sup> units in Eu<sub>4</sub>Fe<sub><i>x</i></sub>(C<sub>2</sub>N<sub>5</sub>)<sub>2</sub> into the guanidinate [CN<sub>3</sub>]<sup>5-</sup> and carbodiimide [CN<sub>2</sub>]<sup>2-</sup> anions. The statistical analysis of the multigrain SCXRD data and DFT-based electronic structure analysis well defined the chemical nature of the bonding in [C<sub>2</sub>N<sub>5</sub>]<sup>7-</sup> and [CN<sub>3</sub>]<sup>5-</sup> anions. This study provides a clear synthetic pathway to a new class of inorganic nitridocarbonates.
Authors
- Fariia Iasmin Akbar (ORCID: https://orcid.org/0000-0002-6016-5849)
- Valentin Kovalev (ORCID: https://orcid.org/0009-0000-0802-4179)
- Christian Tobeck
- Nico Giordano (ORCID: https://orcid.org/0000-0001-9518-1251)
- Dominik Spahr (ORCID: https://orcid.org/0000-0003-0489-5270)
- Mathias S. Wickleder (ORCID: https://orcid.org/0000-0002-8864-4227)
- Anna Pakhomova (ORCID: https://orcid.org/0000-0003-4014-0203)
- Andrey Aslandukov (ORCID: https://orcid.org/0000-0003-0988-6066)
- Nityasagar Jena (ORCID: https://orcid.org/0000-0002-4773-3848)
- Lukas Brüning
- Niko T. Flosbach (ORCID: https://orcid.org/0000-0003-0778-762X)
- Valerio Cerantola (ORCID: https://orcid.org/0000-0002-2808-2963)
- Georgios Aprilis (ORCID: https://orcid.org/0000-0002-0020-9125)
- Pascal L. Jurzick (ORCID: https://orcid.org/0009-0006-3044-3955)
- Maxim Bykov
- Leonid Dubrovinsky (ORCID: https://orcid.org/0000-0002-3717-7585)
- Gaston Garbarino
- Elena Bykova
Institutions
- Linköping University (SE)
- Goethe University Frankfurt (DE)
- University of Cologne (DE)
- Deutsches Elektronen-Synchrotron DESY (DE)
- European Synchrotron Radiation Facility (FR)
- Institute of Inorganic Chemistry of the Slovak Academy of Sciences (SK)
- Environmental Earth Sciences (AU)
- Institute of Geosciences
- University of Bayreuth (DE)
- University of Milano-Bicocca (IT)
Publication Details
- Journal
- Journal of the American Chemical Society
- Published
- 2026-03-04
- DOI
- https://doi.org/10.1021/jacs.5c21756
- Primary Topic
- High-pressure geophysics and materials
- Type
- article
- Field-Weighted Citation Impact
- 0.00