Aggregated initiators: defining their role in the ROP of rac-lactide. Issue 31 (24th May 2018)

• Record Type: Journal Article
• Authors: Cols, Jean-Marie E. P.; Hill, Victoria G.; Williams, Stella K.; McIntosh, Ruaraidh D.
• Is Part Of: Dalton transactions. Volume 47:Issue 31(2018)
• Page Start: 10626
• Page End: 10635
• Publication Date: 2018-05-24
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c8dt01229f
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : Reported examples of aggregated initiators for the ring-opening polymerisation (ROP) of lactide often lack detailed investigations as to the nature of the active species, making it difficult to reconcile ligand design with performance. Abstract : Reported examples of aggregated initiators for the ring-opening polymerisation (ROP) of lactide often lack detailed investigations as to the nature of the active species, making it difficult to reconcile ligand design with performance. Here, we offer additional stability to the polynuclear titanium complexes, TiL (OiPr) (L =9–14 ), through a bridging carboxylate anchored to the supporting amine bis(phenolate) ligands. An in-depth study of solution-state behaviour determined the process of assembly was driven by interactions between the carboxylate and a vacant site on a neighbouring titanium centre. Furthermore, we establish that mononuclear units form dynamic mixtures of polynuclear aggregates, with a clear relationship between nuclearity of the aggregates and the steric bulk on the ligand. Smaller aggregates displayed increased activity towards the ROP of rac -lactide. Furthermore, addition of a chiral centre, on the ligand framework, was investigated as a route to influence the selectivity of the polymerisation via easily-accessible initiators.