Highly Selective and Immortal Magnesium Calixarene Complexes for the Ring-Opening Polymerization of rac-Lactide

Walton, Mark J., Lancaster, Simon J. and Redshaw, Carl (2014) Highly Selective and Immortal Magnesium Calixarene Complexes for the Ring-Opening Polymerization of rac-Lactide. ChemCatChem, 6 (7). pp. 1892-1898. ISSN 1867-3880

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Abstract

The lithiation of 1,3-dipropoxy-p-tert-butylcalix[4]arene (LH2) followed by reaction with nBuMgBr in THF resulted in the formation of the hetero-bimetallic complex [Li(THF)Mg(nBu)L] (1). By contrast, the treatment of tripropoxy-p-tert-butylcalix[4]arene (L′H) with nBu2Mg afforded a mononuclear complex [L′Mg(nBu)] (2). Single-crystal XRD studies revealed that in both structures the calix[4]arene adopts a cone conformation, and a Li cation resides in the cavity for 1. Both 1 and 2 were active for the ring-opening polymerisation of rac-lactide. Compound 2 displayed not only exceptional activity (100 equivalents, 3 min, 92 % conversion, BnOH, room temperature) but also high selectivity (probability to form an r dyad, Pr=0.85) and exhibited an immortal character in THF. Surprisingly, compound 2 also showed isotactic bias (Pr=0.30–0.36) and an immortal character if toluene was employed as the solvent; 2 D J-resolved 1H NMR spectroscopy was employed for the assignment of the stereoselectivity.

Item Type: Article
Uncontrolled Keywords: calixarenes,heterometallic complexes,magnesium,nmr spectroscopy,ring-opening polymerization
Faculty \ School: Faculty of Science > School of Chemistry
Faculty of Science
Depositing User: Pure Connector
Date Deposited: 21 Aug 2014 08:34
Last Modified: 24 Jul 2019 20:14
URI: https://ueaeprints.uea.ac.uk/id/eprint/49971
DOI: 10.1002/cctc.201490040

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