Groups 1, 2 and Zn(II) Heterodinuclear Catalysts for Epoxide/CO2 Ring-Opening Copolymerization

Arron C. Deacy, Christopher B. Durr, Jennifer A. Garden, Andrew J. P. White, Charlotte K. Williams

Research output: Contribution to journalArticlepeer-review

Abstract

A series of heterodinuclear complexes are reported where both Zn(II) and a metal from Group 1 or 2 are chelated by a macrocyclic diphenolate-tetra-amine ligand. The complexes are characterized in the solid state, where relevant by single crystal X–ray crystallography and elemental analysis, and in solution, using NMR spectroscopy and mass spectrometry. The complex synthesis is achieved by reaction of the ligand with diethyl zinc, to form the mono-zinc complex, in situ, followed by subsequent coordination of the second metal; this method enables heterodinuclear conversions >90 % as determined by NMR spectroscopy. Alternatively, the same heterodinuclear complexes are accessed by reaction between the two homodinuclear complexes, at elevated temperatures for extended periods. These findings suggest that most of the heterodinuclear complexes are the thermodynamic products; the only exception is the Na(I)/Zn(II) complex which is unstable with respect to the homodinuclear counterparts. The catalytic activities and selectivity of the stable heterodinuclear complexes are compared, against each other and the relevant homodinuclear analogues, for the ring opening copolymerization (ROCOP) of CO2 and CHO. Nearly all the heterodinuclear complexes are less active than the di-zinc analogues, but the Mg(II)/Zn(II) catalyst is more active. The co-ligand influences the product selectivity, with iodide ligands resulting in cyclic carbonate formation and carboxylate ligands in a high selectivity for polycarbonate.
Original languageEnglish
Pages (from-to)15575-15583
JournalInorganic Chemistry
Volume57
Issue number24
Early online date30 Nov 2018
DOIs
Publication statusPublished - 17 Dec 2018

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