Arca E

Errington RJ

Pascual-Borras M

Penfold T

Waddell PG

Yoshikawa H

English

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 &gt; 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

Pascual-Borràs M

Newcastle University E-Prints

Mechanochemical Polyoxometalate Super-Reduction with Lithium Metal

https://eprints.ncl.ac.uk/file_store/production/294540/E0580896-1E16-495D-AD5F-2080631F86F3.pdf

Mechanochemical Polyoxometalate Super-Reduction with Lithium Metal

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