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Ethyleneglycol tungsten complexes of calix[6 and 8]arenes: Synthesis, characterization and ROP of ε-caprolactone

Zhao, K.-Q.; Li, Y.; Feng, C.; Sun, X.; Li, Yuanzhuo; Zhao, Ke-Qing; Feng, Chun; Elsegood, Mark R.J.; Elsegood, Mark R. J.; Prior, Timothy J.; Sun, Xinsen; Redshaw, Carl; Zhao, Ke Qing

Authors

K.-Q. Zhao

Y. Li

C. Feng

X. Sun

Yuanzhuo Li

Ke-Qing Zhao

Chun Feng

Mark R.J. Elsegood

Mark R. J. Elsegood

Xinsen Sun

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Professor Carl Redshaw C.Redshaw@hull.ac.uk
Professor of Inorganic Materials Chemistry and REF Lead for Chemistry

Ke Qing Zhao



Abstract

By varying the reaction conditions, the reaction of [W(eg)₃] (eg = 1,2-ethanediolato) with p-tert-butylcalix[n]areneHn (n = 6 or 8) in refluxing toluene affords, following work-up, a number of products which have been fully characterized. From the reaction of p-tert-butylcalix[6]areneH₆ with one or two equivalents of [W(eg)₃], only the oxo-bridged complex {[W(eg)]₂(μ-O)p-tert-butylcalix[6]arene} (1) could be isolated, whereas the use of four equivalents of [W(eg)₃], in the presence of molecular sieves, afforded {[W(eg)₂]₂p-tert-butylcalix[6]areneH₂}·2MeCN (2); molecules of 2 pack in bi-layers. Under similar conditions, use of one or two equivalents of [W(eg)₃] and p-tert-butylcalix[8]areneH₈ afforded {[W(eg)]₂p-tert-butylcalix[8]arene}·MeCN (3) in which each tungsten centre was bound by four calixarene oxygens. By contrast, the small orange prisms resulting from the use of four equivalents of [W(eg)₃] and p-tert-butylcalix[8]areneH₈ were shown by synchrotron radiation to be a mixture of two isomers (4a/4b·3.5MeCN). In the major isomer {1,2-[W(eg)₂]₂p-tert-butylcalix[8]areneH₄} (4a), two tungsten centres bind to neighbouring sets of phenolate oxygens, whereas in the minor isomer {1,3-[W(eg)₂]₂p-tert-butylcalix[8]areneH₄} (4b), there is a protonated phenolic group between the two pairs of phenolate oxygens bound to tungsten; the major:minor ratio is about 83:17. Use of p-tert-butyltetrahomodioxacalix[6]areneH₆ with two equivalents of [W(eg)₃] resulted in the isolation of {[WO(eg)]₂p-tert-butyltetrahomodioxacalix[6]areneH₂} (5·0.83toluene·MeCN), in which each dimethyleneoxa bridge is bound to an oxotungsten(VI) centre. Complexes 1–5, together with the known complex [W(eg)p-tert-butylcalix[4]arene] (6), have been screened for their ability to ring open polymerize (ROP) ε-caprolactone; for 1, 2 and 5, 6 conversion rates were good (>88%) at 110 °C over 12 or 24 h, whereas the calix[8]arene complexes 3 and 4 under the same conditions were inactive.

Citation

Li, Y., Zhao, K., Feng, C., Elsegood, M. R., Prior, T. J., Sun, X., & Redshaw, C. (2014). Ethyleneglycol tungsten complexes of calix[6 and 8]arenes: Synthesis, characterization and ROP of ε-caprolactone. Dalton transactions : an international journal of inorganic chemistry / RSoC, 43(36), 13612-13619. https://doi.org/10.1039/c4dt01936a

Journal Article Type Article
Acceptance Date Jul 23, 2014
Online Publication Date Jul 28, 2014
Publication Date Sep 28, 2014
Deposit Date Jun 9, 2015
Publicly Available Date Jun 9, 2015
Journal Dalton transactions
Print ISSN 1477-9226
Electronic ISSN 1477-9234
Publisher Royal Society of Chemistry
Peer Reviewed Peer Reviewed
Volume 43
Issue 36
Pages 13612-13619
DOI https://doi.org/10.1039/c4dt01936a
Keywords Ethyleneglycol tungsten complexes , Synthesis, ε-caprolactone
Public URL https://hull-repository.worktribe.com/output/374941
Publisher URL http://pubs.rsc.org/en/Content/ArticleLanding/2014/DT/C4DT01936A#!divAbstract
Additional Information Author's accepted manuscript of article published in: Dalton transactions, 2014, v.43, issue 36.

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