Dinuclear iminophenoxide copper complexes in rac-lactide polymerisationElectronic supplementary information (ESI) available: Additional graphics and tables, NMR spectra of ligands, and details of X-ray diffraction analysis (CIF). CCDC 1845023-1845034, 1845044-1845052. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c8dt02140f

• Main Authors: Daneshmand, Pargol, Pinon, Leena, Schaper, Frank
• Format: Journal Article
• Published: 31.07.2018
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c8dt02140f

Dinuclear bis(R′-(R′′-iminomethyl)phenoxide) copper complexes L 2 Cu 2 (μ-OR) 2 were prepared from the reaction of copper methoxide with ROH and LH (ROH = dimethylaminoethanol or pyridylmethanol, R′ = H, 4,6- t Bu, 1,3-Cl, R′′ = benzyl, cyclohexyl, diphenylmethyl and 2,6-dimethylphenyl). Preparation was complicated by formation of homoleptic L 2 Cu and only 9 of the 24 possible combinations could be prepared. All complexes were characterized by single crystal X-ray diffraction studies and crystallized as dinuclear penta-coordinated complexes. Homoleptic complexes L 2 Cu were inactive in lactide polymerization at room temperature. Most heteroleptic complexes showed modest to good activities with full conversion in less than 6 h at room temperature. Complexes with R′ = H showed poor molecular weight control, complexes with R′ = Cl were inactive in polymerization. In pyridylmethoxide-containing complexes, only one alkoxide initiated chain growth. All complexes produced atactic polymer. Bis(R′-(R′′-iminomethyl)phenoxide) copper complexes closely resemble their iminopyrrolide analogs in structure, reactivity, and in the dinuclear active species. However, while they provide good polymer molecular weight control, they produce only atactic polylactide.