The Biicosahedral Complex Anions [M(B <sub>11</sub> H <sub>11</sub> ) <sub>2</sub> ] <sup>3−</sup> (M = Cu, Ag, Au): Synthesis and Unexpected Low‐Temperature Phase Transition of [Ag(η <sup>5</sup> ‐B <sub>11</sub> H <sub>11</sub> ) <sub>2</sub> ] <su
We disclose the synthesis and properties of [M(B<sub>11</sub>H<sub>11</sub>)<sub>2</sub>]<sup>3-</sup> (M = Cu, Ag, Au) with the first gold-based anion [Au(B<sub>11</sub>H<sub>11</sub>)<sub>2</sub>]<sup>3-</sup>. The nido-[B<sub>11</sub>H<sub>11</sub>]<sup>4-</sup> ligand stabilizes complexes with copper, silver, and gold in the highest known oxidation state +V. The relative stability of [M<sup>+V</sup>(nido-B<sub>11</sub>X<sub>11</sub>)<sub>2</sub>]<sup>3-</sup>, [M<sup>+III</sup>(nido-B<sub>11</sub>X<sub>11</sub>)(closo-B<sub>11</sub>X<sub>11</sub>)]<sup>3-</sup>, and [M<sup>+I</sup>(closo-B<sub>11</sub>X<sub>11</sub>)<sub>2</sub>]<sup>3-</sup> isomers (X = H, F) was calculated at the DFT level. Unlike for [Cu(B<sub>11</sub>H<sub>11</sub>)<sub>2</sub>]<sup>3-</sup> and [Au(B<sub>11</sub>H<sub>11</sub>)<sub>2</sub>]<sup>3-</sup>, in case of [Ag(B<sub>11</sub>H<sub>11</sub>)<sub>2</sub>]<sup>3-</sup>, we discovered the equilibrium between the kinetically stable [Ag<sup>+V</sup>(nido-B<sub>11</sub>H<sub>11</sub>)<sub>2</sub>]<sup>3-</sup> (η<sup>5</sup>) and kinetically labile [Ag<sup>+I</sup>(closo-B<sub>11</sub>H<sub>11</sub>)<sub>2</sub>]<sup>3-</sup> (η<sup>2</sup>) by X-ray diffraction. The isomerization of the Ag complex shows signs of Ag(V)-Ag(I) redox processes. When a crystal is cooled, a phase transition occurs at 110-130 K in which the coordination of the ligands on the silver changes from η<sup>5</sup> to η<sup>2</sup>. The phase transition is reversible and upon heating to 170 K, the η<sup>2</sup> to η<sup>5</sup> coordination is transformed. The reaction of [M(B<sub>11</sub>H<sub>11</sub>)<sub>2</sub>]<sup>3-</sup> with HF leads to the partial substitution of hydrogen atoms by fluorine atoms to form [M(B<sub>11</sub>H<sub>11-x</sub>F<sub>x</sub>)<sub>2</sub>]<sup>3-</sup> (M = Cu, Au; x ≈ 4). We synthesized 18 compounds containing [M(B<sub>11</sub>H<sub>11</sub>)<sub>2</sub>]<sup>3-</sup> (M = Cu, Ag, Au) and their derivatives, followed by structural determination (X-ray crystallography). XANES data confirm the high oxidation state of Cu in K<sub>3</sub>[Cu(B<sub>11</sub>H<sub>11</sub>)<sub>2</sub>]·5H<sub>2</sub>O.
Authors
- Adam Slabon (ORCID: https://orcid.org/0000-0002-4452-1831)
- Eduard Bernhardt (ORCID: https://orcid.org/0000-0002-0350-3231)
- Alexey Maximenko (ORCID: https://orcid.org/0000-0003-2660-8105)
- Tobias Preitschopf (ORCID: https://orcid.org/0000-0002-7288-3004)
- Maik Finze (ORCID: https://orcid.org/0000-0002-6098-7148)
- Björn B. Beele (ORCID: https://orcid.org/0000-0001-5888-8952)
- Andreas Drichel (ORCID: https://orcid.org/0000-0001-5895-1608)
- Tanja Knuplez (ORCID: https://orcid.org/0009-0005-3228-0064)
Institutions
- Jagiellonian University (PL)
- University of Wuppertal (DE)
- University of Würzburg (DE)
Publication Details
- Journal
- Angewandte Chemie International Edition
- Published
- 2025-11-10
- DOI
- https://doi.org/10.1002/anie.202519283
- Citations
- 1
- Primary Topic
- Boron Compounds in Chemistry
- Type
- article
- Field-Weighted Citation Impact
- 1.36