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

Lookup NU author(s): Dr John Errington, Dr Sagar Petkar, Paul Middleton, Emeritus Professor William McFarlane, Emeritus Professor Bill Clegg, Dr Ross Harrington

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Abstract

The tetra-n-butylammonium (TBA) salt of [(MeO)TiW5O 18]3- 1 was reacted with alcohols ROH to give primary, secondary and tertiary alkoxide derivatives [(RO)TiW5O 18]3- (R = Et 2, iPr 3 and tBu 4), whilst hydrolysis afforded [(-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 TiO bond formation via reactions analogous to those occurring at the surfaces of solid heteropolyacids. Aryloxides [(ArO)TiW5O 18]3- were prepared by reacting 1 with phenols ArOH (Ar = C6H5 6, C6H4Me-4 7, C 6H4tBu-4 8, C6H4OH-4 9, C6H4OH-3 10, C6H3(OH) 2-3,5 11 and C6H4CHO-2 13). TiW 5O18 units were linked by reacting 1 with 9 to give [(-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. This journal is © The Royal Society of Chemistry.


Publication metadata

Author(s): Errington RJ, Petkar SS, Middleton PS, McFarlane W, Clegg W, Coxall RA, Harrington RW

Publication type: Article

Publication status: Published

Journal: Dalton Transactions

Year: 2007

Issue: 44

Pages: 5211-5222

Date deposited: 05/07/2010

ISSN (print): 1477-9226

ISSN (electronic): 1477-9234

Publisher: Royal Society of Chemistry

URL: http://dx.doi.org/10.1039/b709732h

DOI: 10.1039/b709732h


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