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Ghosh, Swarup ; Schulte, Yannick ; Wölper, Christoph ; Tjaberings, Alexander ; Gröschel, André H. ; Haberhauer, Gebhard ; Schulz, Stephan:
Cooperative Effect in Binuclear Zinc Catalysts in the ROP of Lactide.
In: Organometallics.
Bd. 41
(2022)
Heft 19
.
- S. 2698-2708.
ISSN 1520-6041
DOI: https://doi.org/10.1021/acs.organomet.2c00333
Abstract
Binuclear monomeric L1Zn2R2 (R = Me 1 and Et 2; L2Zn2R2, R = Me 3 and Et 4) and dimeric ketodiiminate zinc alkyl complexes [L1(H)ZnR]2 (R = Me 5 and Et 6; L1 = (Me2NC2H4NC (Me)CH)2CO, L2 = (Me2NC3H6NC(Me)CH)2CO) were synthesized and spectroscopically characterized (1H and 13C NMR and IR). Diffusion-ordered NMR spectroscopy and single-crystal X-ray diffraction analysis (1, 2, and 4–6) proved their monomeric (1–4) and dimeric (5 and 6) structures in solution and solid states. Their catalytic activity in the ring-opening polymerization of lactide was studied under various conditions and compared to mononuclear β-ketoimine zinc complexes 7–10. Initiation reactions of the Et-substituted complexes 2, 4, and 6 are faster than for the corresponding Me-substituted complexes 1, 3, and 5, and kinetic studies with catalyst 2 proved the first-order dependency on both the monomer and the catalyst concentration. Quantum chemical calculations revealed that the activation barriers for the addition of CH3– to L-LA via a mononuclear mechanism for the mono- (7) and binuclear (1) Me-substituted and the corresponding MeO-substituted complexes 1-OMe and 7-OMe, which are regarded as model compounds of the “active” catalyst, are similar. However, while the binuclear mechanism for complex 1 is slightly higher in energy than for the mononuclear mechanism, the binuclear pathway for the MeO-substituted complex 1-OMe is favored, clearly proving the beneficial cooperative effect between the two adjacent zinc atoms.
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| Publikationsform: | Artikel in einer Zeitschrift |
|---|---|
| Begutachteter Beitrag: | Ja |
| Institutionen der Universität: | Forschungseinrichtungen > Zentrale wissenschaftliche Einrichtungen > Bayerisches Zentrum für Batterietechnik - BayBatt Forschungseinrichtungen Forschungseinrichtungen > Zentrale wissenschaftliche Einrichtungen Fakultäten > Fakultät für Biologie, Chemie und Geowissenschaften > Fachgruppe Chemie > Lehrstuhl Polymermaterialien für elektrochemische Speicher > Lehrstuhl Polymermaterialien für elektrochemische Speicher - Univ.-Prof. Dr. André Gröschel |
| Titel an der UBT entstanden: | Nein |
| Themengebiete aus DDC: | 500 Naturwissenschaften und Mathematik > 540 Chemie |
| Eingestellt am: | 27 Jul 2023 11:07 |
| Letzte Änderung: | 02 Aug 2023 07:53 |
| URI: | https://eref.uni-bayreuth.de/id/eprint/86371 |