Journal
CHEMISTRY-A EUROPEAN JOURNAL
Volume 27, Issue 19, Pages 5913-5918Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/chem.202100482
Keywords
aluminum; N-heterocyclic carbenes; phosphinidenes; poly(lactic acid); ring-opening polymerization
Categories
Funding
- Deutsche Forschungsgemeinschaft (DFG) [TA 189/16-1]
Ask authors/readers for more resources
The NHC-phosphinidene adducts reacted with AlMe3 to generate monoaluminum and dialuminum complexes, which were found to act as efficient initiators for ring-opening polymerization of rac-lactide. The monoaluminum complexes produced highly isoselective poly(rac-lactide), while the dialuminum complex resulted in almost atactic polymers, indicating the importance of the coordination-insertion mechanism with carbene-phosphinidene ligands as stereodirecting groups.
The N-heterocyclic carbene-phosphinidene adducts (NHC)PH were reacted with AlMe3 in toluene to afford the monoaluminum complexes [{(IDipp)PH}AlMe3] and [{(IMes)PH}AlMe3] (IDipp=1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene, IMes=1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene). In contrast, the dialuminum complex [{((Me)IMes)PH}(AlMe3)(2)] was obtained for (Me)IMes=1,3-bis(2,4,6-trimethylphenyl)-4,5-dimethylimidazolin-2-ylidene. These complexes served as initiators for the efficient ring-opening polymerization of rac-lactide in toluene at 60 degrees C. High degrees of isoselectivity were found for the poly(rac-lactide) obtained in the presence of the monoaluminum complexes (P-m up to 0.92, T-m up to 191 degrees C), whereas almost atactic polymers were produced by the dialuminum complex. Detailed mechanistic studies reveal that the polymerization proceeds via a coordination-insertion mechanism with the carbene-phosphinidene ligands acting as stereodirecting groups.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available