Issue 7, 2014

Ethyl 2-hydroxy-2-methylpropanoate derivatives of magnesium and zinc. The effect of chelation on the homo- and copolymerization of lactide and ε-caprolactone

Abstract

The preparation, single crystal and molecular structures of the compounds (BDI)Mg(OCMe2COOEt)(L) are described where BDI = 2-[(2,6-diisopropylphenyl)amino]-4-[(2,6-diisopropylphenyl)imino]pent-2-ene and L = pyridine (py) and 4-dimethylaminopyridine (DMAP). In the solid-state the molecules have five coordinate Mg2+ ions that may be considered as derived from a trigonal bipyramid where the chelating BDI and OCMe2COOEt ligands span equatorial-axial sites. IR spectroscopic data obtained in CH2Cl2 indicate that the chelating nature of the OCMe2COOEt ligand is maintained in solution and variable temperature NMR studies reveal that the ligands py or DMAP undergo a rapid reversible dissociation in toluene-d8 and especially in THF-d8. This leads to a facile exchange involving coordinated and free L upon the addition of L and evidence is presented to support the view that this occurs exclusively by a dissociative interchange mechanism. Zinc forms a related complex (BDI)Zn(OCMe2COOEt) lacking additional coordination of L but maintaining the chelating nature of the OCMe2COOEt ligand and undergoing reversible coordination of L in the presence of added ligands L. The magnesium and zinc complexes will initiate and sustain the living polymerization of lactide (L- or rac-LA) but not the ring-opening polymerization of ε-caprolactone.

Graphical abstract: Ethyl 2-hydroxy-2-methylpropanoate derivatives of magnesium and zinc. The effect of chelation on the homo- and copolymerization of lactide and ε-caprolactone

Supplementary files

Article information

Article type
Paper
Submitted
16 Sep 2013
Accepted
29 Oct 2013
First published
30 Oct 2013

Dalton Trans., 2014,43, 2781-2788

Ethyl 2-hydroxy-2-methylpropanoate derivatives of magnesium and zinc. The effect of chelation on the homo- and copolymerization of lactide and ε-caprolactone

V. Balasanthiran, M. H. Chisholm, K. Choojun and C. B. Durr, Dalton Trans., 2014, 43, 2781 DOI: 10.1039/C3DT52553H

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