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

Jean-Marie Cols, Cameron E. Taylor, Kevin J. Gagnon, Simon J. Teat, Ruaraidh D McIntosh

Research output: Contribution to journalArticle

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.
Original languageEnglish
Pages (from-to)17729-17738
Number of pages10
JournalDalton Transactions
Volume45
Issue number44
Early online date17 Oct 2016
DOIs
Publication statusPublished - 28 Nov 2016

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Ring opening polymerization
Titanium
Amines
Catalyst activity
Moisture
Nuclear magnetic resonance
Ligands
Catalysts
Air
Experiments
Temperature
dilactide

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Cols, Jean-Marie ; Taylor, Cameron E. ; Gagnon, Kevin J. ; Teat, Simon J. ; McIntosh, Ruaraidh D. / Well-defined Ti4 pre-catalysts for the ring-opening polymerisation of lactide. In: Dalton Transactions. 2016 ; Vol. 45, No. 44. pp. 17729-17738.
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Well-defined Ti4 pre-catalysts for the ring-opening polymerisation of lactide. / Cols, Jean-Marie; Taylor, Cameron E.; Gagnon, Kevin J.; Teat, Simon J.; McIntosh, Ruaraidh D.

In: Dalton Transactions, Vol. 45, No. 44, 28.11.2016, p. 17729-17738.

Research output: Contribution to journalArticle

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AB - 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.

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