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Protonolysis and Condensation Reactions of Alkoxido-Substituted Lindqvist {MW5} and Keggin {MPW11} Polyoxometalates: Comparative Experimental and Modelling Studies.

Lookup NU author(s): Daniel Lebbie, Dr Thompson Izuagie, Dr Magda Pascual-BorrasORCiD, Balamurugan Kandasamy, Dr Corinne Wills, Dr Paul Waddell, Dr Ben HorrocksORCiD, Dr John ErringtonORCiD

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This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).


Abstract

An understanding of proton transfer and migration at the surfaces of solid metal oxides and related molecular polyoxometalates (POMs) and metal alkoxides is crucial for the development of reactivity involving protonation or the absorption/binding of water. In this work, the hydrolysis of alkoxido Ti- and Sn-substituted Lindqvist [(MeO)MW5O18]3–(M = Ti, 1; M = Sn, 2) and Keggin [(MeO)MPW11O39]4– (M = Ti, 3; M = Sn, 4) type polyoxometalates (POMs) to hydroxido derivatives and subsequent condensation to µ-oxido species has been investigated in detail to provide insight into proton transfer reactions in these molecular metal oxide systems. Solution NMR studies revealed the dependence of reactions not only on the nature of the heteroatom (Ti or Sn) but also on the type of lacunary (MW5 or PW11) POM and also on the solvent (MeCN or DMSO). Tin-substituted anions 2 and 4 were much more susceptible to protonolysis than the Ti analogues 1 and 3 while reactions of {MW5} anions were generally faster than those of the {MPW11} anions. Subsequent condensation of the resulting hydroxido derivatives [(HO)MW5O18]3– (M = Ti, 5; M = Sn, 6) and [(HO)MPW11O39]4– (M = Ti, 7; M = Sn, 8) was significantly more facile for 5 and 7 and, in all cases, condensation was inhibited in DMSO. Quantitative comparisons of equilibria and reaction rates were provided by analysis of NMR kinetic experiments, while DFT calculations on these and the analogous {NbW5} reactions provided comparative energetics and reaction profiles that are consistent with experimental observations. These results add to the fundamental understanding of proton migration in metal alkoxide hydrolysis/condensation and related reactions at metal oxide surfaces.


Publication metadata

Author(s): Lebbie D, Izuagie T, Pascual-Borras M, Kandasamy B, Wills C, Waddell PG, Horrocks BR, Errington RJ

Publication type: Article

Publication status: Published

Journal: Inorganic Chemistry

Year: 2025

Volume: 649

Issue: 5

Pages: 2379–2393

Print publication date: 29/01/2025

Online publication date: 29/01/2025

Acceptance date: 22/01/2025

Date deposited: 28/01/2025

ISSN (print): 0020-1669

ISSN (electronic): 1520-510X

Publisher: American Chemical Society

URL: https://doi.org/10.1021/acs.inorgchem.4c04636

DOI: 10.1021/acs.inorgchem.4c04636

Data Access Statement: CCDC 2389467-39 2389468 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, by emailing data_request@ccdc.cam.ac.uk, or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge


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Funding

Funder referenceFunder name
EPRSC for financial support through the INPOMS UK-Japan Core-to-Core Network Grant(EP/S031170/1)

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