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Lookup NU author(s): Dr Magda Pascual-BorrasORCiD, Dr Elisabetta Arca, Professor Thomas Penfold, Dr Paul Waddell, Dr John ErringtonORCiD
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
In this first systematic investigation of mechanochemical polyoxometalate (POM) reduction, (TBA)3[PMo12O40] was reacted with n equivalents of lithium metal (n = 1 – 24) to generate PMo12/n products which were shown to be mixtures of electron-rich PMo12Lix species. FTIR analysis revealed the lengthening/weakening of terminal Mo=O bonds with increasing levels of reduction, while EXAFS spectra indicated the onset of Mo–Mo bond formation at n ~ 8 and a significant structural change at n > 12. Successive MoVI reductions were monitored by XANES and XPS and, at n = 24, results were consistent with the formation of at least one MoIV–MoIV bonded {MoIV3} triad together with MoV. Upon dissolution, the PMo12Lix species present in the solid PMo12/n products undergo electron exchange and single-peak 31P NMR spectra were observed for n = 1 – 12. For n ≥ 16, changes in solid state and solution 31P NMR spectra coincided with the emergence of features in the UV-vis spectra associated with MoV-MoV and {MoIV3} bonding in an ε-Keggin structure. Bonding between {Li(NCMe)}+ and 2-electron-reduced PMo12 in the crystal structure of (TBA)4[PMo12O40{Li(NCMe)}] suggested that stronger Li–O interactions in more highly reduced products could result in lithium-oxide-promoted TBA cation decomposition and POM degradation, which might explain the appearance of XPS peaks for Mo2C at n ≥ 16. This work revealed some of the complex, unexplored chemistry of super-reduced POMs and establishes a new, solvent-free approach in the search for a better fundamental understanding of the electronic properties and reactivity of electron-rich nanoscale metal oxides.
Author(s): Pascual-Borràs M, Arca E, Yoshikawa H, Penfold T, Waddell PG, Errington RJ
Publication type: Article
Publication status: Published
Journal: Journal of the American Chemical Society
Year: 2024
Pages: ePub ahead of print
Online publication date: 10/09/2024
Acceptance date: 01/09/2024
Date deposited: 02/09/2024
ISSN (print): 0002-7863
ISSN (electronic): 1520-5126
Publisher: American Chemical Society
URL: https://doi.org/10.1021/jacs.4c09998
DOI: 10.1021/jacs.4c09998
Data Access Statement: The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/jacs.4c09998. CCDC 2305190-2305191 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing data_request@ccdc.cam.ac.uk, or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
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