Aluminium complexes containing N,N′-chelating amino-amide hybrid ligands applicable for preparation of biodegradable polymers

• Mononuclear aluminium complexes were prepared.
• N,N'-chelating ligands were used.
• Ring opening (co)polymerizations of ε-caprolactone and trimethylene carbonate were initiated by title complexes.
• Esterification of l-lactide initiated by dimethylaluminium complex led selectively to methyl (S,S)-O-lactyllactate.

Five aluminium complexes containing N,N'-chelating ligands ([2-(Me2NCH2)C6H4N(R)]−; R = H, SiMe3 or benzyl (Bn)) were prepared and structurally characterized by NMR and crystallographic techniques. Aluminium atoms in all compounds are pseudotetrahedrally coordinated with extremely short intramolecular interaction of the pendant amino group (d(Al–N) = 1.96–2.00 Å). The catalytic performance of selected complexes (∼0.1–0.2 mol. %), either with or without an external co-initiator, in ring opening (co)polymerization of ε-caprolactone, l-lactide and trimethylene carbonate was tested yielding satisfactory to excellent amount of polymeric material with Mn ∼ 15–70 kg/mol for ε-caprolactone, and ∼30 kg/mol for trimethylene carbonate with good degree of control over the molar mass distribution, initiation efficiency. An excellent conversion of l-lactide to methyl (S,S)-O-lactyllactate is observed upon catalysis by one of the complexes at room temperature.

Mononuclear aluminium complexes containing N,N'-chelating ligands ([2-(Me2NCH2)C6H4N(R)]−; R = H, SiMe3 or benzyl (Bn)) were prepared and structurally characterized. Selected complexes were tested as precursors of catalytically active species in ring opening (co)polymerization of ε-caprolactone, l-lactide and trimethylene carbonate.Figure optionsDownload as PowerPoint slide