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Issue 44, 2007
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Non-aqueous synthetic methodology for TiW5 polyoxometalates: protonolysis of [(MeO)TiW5O18]3− with alcohols, water and phenols

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Abstract

The tetra-n-butylammonium (TBA) salt of [(MeO)TiW5O18]3−1 was reacted with alcohols ROH to give primary, secondary and tertiary alkoxide derivatives [(RO)TiW5O18]3− (R = Et 2, iPr 3 and tBu 4), whilst hydrolysis afforded [(µ-O)(TiW5O18)2]6−5 rather than the hydroxo derivative (R = H). In reactions with iPrOH and tBuOH, impurity peaks observed at 1015 and 1020 ppm in the 17O NMR spectra indicate alkoxide degradation and Ti[double bond, length as m-dash]O bond formation via reactions analogous to those occurring at the surfaces of solid heteropolyacids. Aryloxides [(ArO)TiW5O18]3− were prepared by reacting 1 with phenols ArOH (Ar = C6H56, C6H4Me-4 7, C6H4tBu-4 8, C6H4OH-4 9, C6H4OH-3 10, C6H3(OH)2-3,5 11 and C6H4CHO-2 13). TiW5O18 units were linked by reacting 1 with 9 to give [(µ-1,4-OC6H4O)(TiW5O18)2]6−12. 17O and 183W NMR spectra are reported and X-ray crystal structures were obtained for TBA salts of anions 3–10 and 13, which showed that the titanium is six-coordinate in all cases. Reactions were monitored by 1H NMR, including a 2D-EXSY study of methoxo exchange, and the slow rates observed are probably associated with the reluctance of titanium in these anions to achieve seven-coordination.

Graphical abstract: Non-aqueous synthetic methodology for TiW5 polyoxometalates: protonolysis of [(MeO)TiW5O18]3− with alcohols, water and phenols

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Publication details

The article was received on 27 Jun 2007, accepted on 01 Aug 2007 and first published on 06 Sep 2007


Article type: Paper
DOI: 10.1039/B709732H
Citation: Dalton Trans., 2007, 5211-5222
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    Non-aqueous synthetic methodology for TiW5 polyoxometalates: protonolysis of [(MeO)TiW5O18]3− with alcohols, water and phenols

    R. J. Errington, S. S. Petkar, P. S. Middleton, W. McFarlane, W. Clegg, R. A. Coxall and R. W. Harrington, Dalton Trans., 2007, 5211
    DOI: 10.1039/B709732H

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