Stabilization of the Oxidation State +IV in Siloxide‐Supported Terbium Compounds

The synthesis of lanthanides other than cerium in the oxidation state +IV has remained a desirable but unmet target until recently, when two examples of TbIV with saturated coordination spheres were isolated. Here we report the third example of an isolated molecular complex of terbium(IV), where the...

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Bibliographic Details
Published in:Angewandte Chemie International Edition 2020-02, Vol.59 (9), p.3549-3553
Main Authors: Willauer, Aurélien R., Palumbo, Chad T., Scopelliti, Rosario, Zivkovic, Ivica, Douair, Iskander, Maron, Laurent, Mazzanti, Marinella
Format: Article
Language:English
Subjects:
Cerium
Computer applications
Coordination
Electron transfer
Lanthanides
Ligands
Metal ions
metal-ion-coupled electron transfer
Oxidation
rare earths
siloxides
Stability
Terbium
Terbium compounds
Valence
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Summary:The synthesis of lanthanides other than cerium in the oxidation state +IV has remained a desirable but unmet target until recently, when two examples of TbIV with saturated coordination spheres were isolated. Here we report the third example of an isolated molecular complex of terbium(IV), where the supporting siloxide ligands do not saturate the coordination sphere. The fully characterized six‐coordinate complex [TbIV(OSiPh3)4(MeCN)2], 2‐TbPh, shows high stability and the labile MeCN ligands can be replaced by phosphinoxide ligands. Computational studies suggest that the stability is due to a strong π(O−Tb) interaction which is stronger than in the previously reported TbIV complexes. Cyclic‐voltammetry experiments demonstrate that non‐binding counterions contribute to the stability of TbIV in solution by destabilizing the +III oxidation state, while alkali ions promote TbIV/TbIII electron transfer. TbIV is here to stay: The terbium(IV) complex [Tb(OSiPh3)4(MeCN)2] contains labile ligands but shows high stability as a result of a strong π(O−Tb) interaction. Non‐binding counterions contribute to the stability of TbIV in solution by destabilizing the oxidation state +III, while alkali ions promote TbIV/TbIII electron transfer.
ISSN:1433-7851
1521-3773
DOI:10.1002/anie.201914733