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oai:docta.ucm.es:20.500.14352/1186512025-03-18T13:58:04Zcom_20.500.14352_14col_20.500.14352_15

Exploiting the Reactivity of Metal Trifluoroacetates to Access Alkali–Niobium(V) Oxyfluorides Imer, Marcos R. Szlag, Regina G. Oreskovic, Benjamin D. E. Urones Garrote, Esteban García Martín, Susana Rabuffetti, Federico A. 547 Atmospheric chemistry Crystal structure Diffraction Mixtures Precursors Ciencias 23 Química Motivated by the lack of facile routes to alkali–niobium(V) oxyfluorides KNb2O5F and CsNb2O5F, we investigated the reactivity of alkali trifluoroacetates KH(tfa)2 and CsH(tfa)2 (tfa = CF3COO–) toward Nb2O5 in the solid state. Tetragonal tungsten bronze KNb2O5F and pyrochlore CsNb2O5F were obtained by simply reacting the corresponding trifluoroacetate with Nb2O5 at 600 °C under air, without the need for specialized containers or a controlled atmosphere. Thermolysis of KH(tfa)2 in the presence of Nb2O5 yielded single-phase polycrystalline KNb2O5F. By contrast, the reaction between CsH(tfa)2 and Nb2O5 produced a mixture of CsNb2O5F and a new oxyfluoride of formula CsNb3O7F2, whose crystal structure was solved using powder X-ray and electron diffraction. CsNb3O7F2 (space group P6/mmm) belongs to the family of hexagonal tungsten bronzes and features an open-framework structure consisting of corner-sharing Nb(O,F)6 octahedra with hexagonal channels occupied by Cs+ ions. Isomorphous RbNb3O7F2 was obtained upon reacting RbH(tfa)2 with Nb2O5. Synthetic optimization enabled the preparation of RbNb3O7F2 and CsNb3O7F2 as single-phase polycrystalline solids at 500 °C under flowing synthetic air. Both oxyfluorides were found to be semiconductors with a band gap of ≈3.5 eV. The discovery of these two oxyfluorides highlights the importance of probing the reactivity of solids whose full potential as fluorinated precursors is yet to be realized. Ministerio de Ciencia e Inovación (España) Depto. de Química Inorgánica Fac. de Ciencias Químicas TRUE pub 2025-03-11T09:13:58Z 2025-03-11T09:13:58Z 2024-06-10 journal article VoR https://hdl.handle.net/20.500.14352/118651 XXXX-XXXX 10.1021/acs.inorgchem.4c01700 eng PID2022- 139039OB-C22 Imer, Marcos R., et al. «Exploiting the Reactivity of Metal Trifluoroacetates to Access Alkali–Niobium(V) Oxyfluorides». Inorganic Chemistry, vol. 63, n.o 25, junio de 2024, pp. 11842-51. DOI.org (Crossref), https://doi.org/10.1021/acs.inorgchem.4c01700. Attribution-NonCommercial-NoDerivatives 4.0 International http://creativecommons.org/licenses/by-nc-nd/4.0/ open access application/pdf ACS