File(s) not publicly available

Reason: This item is currently closed access.

Tetraphenolate niobium and tantalum complexes for the ring opening polymerization of epsilon-caprolactone

journal contribution
posted on 07.09.2015 by Yahya Al-Khafaji, Xinsen Sun, Timothy J. Prior, Mark Elsegood, Carl Redshaw
Reaction of the pro-ligand α,α,α’,α’-tetra(3,5-di-tert-butyl-2-hydroxyphenyl-p-)xylene-para-tetraphenol (p-L1H4) with two equivalents of [NbCl5] in refluxing toluene afforded, after work-up, the complex {[NbCl3(NCMe)]2(μ-p-L1)}·6MeCN (1·6MeCN). When the reaction was conducted in the presence of excess ethanol, the orange complex {[NbCl2(OEt)(NCMe)]2(μ-p-L1)}·312 MeCN·0.614toluene (2·312 MeCN·0.614toluene) was formed. A similar reaction using [TaCl5] afforded the yellow complex {[TaCl2(OEt)(NCMe)]2(μ-p-L1)}·5MeCN (3·5MeCN). In the case of the meta pro-ligand, namely α,α,α’,α’tetra (3,5-di-tert-butyl-2-hydroxyphenyl-m-)xylene-meta-tetraphenol (m-L2H4) only the use of [Nb(O)- Cl3(NCMe)3] led to the isolation of crystalline material, namely the orange bis-chelate complex {[Nb-(NCMe)Cl(m-L2H2)2]}·312 MeCN (4·312MeCN) or {[Nb(NCMe)Cl(m-z2H2)2]}·5MeCN (4·5MeCN). The molecular structures of 1–4 and the tetraphenols L1H4 and m-L2H4·2MeCN have been determined. Complexes 1–4 have been screened as pre-catalysts for the ring opening polymerization of ε-caprolactone, both with and without benzyl alcohol or solvent present, and at various temperatures; conversion rates were mostly excellent (>96%) with good control either at >100 °C over 20 h (in toluene) or 1 h (neat).

History

School

  • Science

Department

  • Chemistry

Published in

DALTON TRANSACTIONS

Volume

44

Issue

27

Pages

12349 - 12356 (8)

Citation

AL-KHAFAJI, Y. ...et al., 2015. Tetraphenolate niobium and tantalum complexes for the ring opening polymerization of epsilon-caprolactone. Dalton Transactions, 44(27), pp.12349-12356.

Publisher

© The Royal Society of Chemistry

Version

AM (Accepted Manuscript)

Publisher statement

This work is made available according to the conditions of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) licence. Full details of this licence are available at: https://creativecommons.org/licenses/by-nc-nd/4.0/

Publication date

2015

Notes

This paper is in closed access.

ISSN

1477-9226

Language

en

Exports

Logo branding

Keyword(s)

Exports