Issue 44, 2016

Well-defined Ti4 pre-catalysts for the ring-opening polymerisation of lactide

Abstract

The synthesis and full characterisation of four discrete tetrametallic titanium complexes is reported. These well-defined compounds are isostructural in the solid state and share the same general formula: Ti4(μ-O)2L4 (L = 1, 2, 3 or 4). Using a combination of NMR techniques the complexes are found to be stable in solution, even at elevated temperatures. Further studies show that the carboxylate moieties of the supporting amine bis(phenolate) ligands can be displaced by a more strongly coordinating solvent. This reversible process causes the coordinatively saturated Ti4(μ-O)2L4 complexes to separate into two Ti2(μ-O)L2 subunits which we envisaged would be catalytically active. Proof-of-concept experiments establish that all four of these complexes display catalytic activity in the ring-opening polymerisation of rac-lactide. These aggregates can therefore be viewed as air and moisture stable pre-catalysts for a range of reactions.

Graphical abstract: Well-defined Ti4 pre-catalysts for the ring-opening polymerisation of lactide

Supplementary files

Article information

Article type
Paper
Submitted
04 Oct 2016
Accepted
17 Oct 2016
First published
17 Oct 2016

Dalton Trans., 2016,45, 17729-17738

Well-defined Ti4 pre-catalysts for the ring-opening polymerisation of lactide

J. E. P. Cols, C. E. Taylor, K. J. Gagnon, S. J. Teat and R. D. McIntosh, Dalton Trans., 2016, 45, 17729 DOI: 10.1039/C6DT03842E

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