Lactide Polymerization with Chiral β-Diketiminate Zinc Complexes
Why this work is in the frame
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Bibliographic record
Abstract
N, N ′-Di( S -phenylethyl)-2-amino-4-iminopent-2-ene, S,S - nacnac CH(Me)Ph H, 1a, and N, N ′-dibenzyl-2-amino-4-iminopent-2-ene, nacnac Bn H, 1b, react with ZnEt 2 to form the corresponding nacnac ZnEt complexes 2a and 2b . Neither complex is reactive with 2-propanol or methyl lactate to produce the corresponding alkoxide complexes. In reactions with 2b, ligand redistribution occurs and nacnac Bn 2 Zn was obtained. Reaction of 1a and 1b with Zn(N(SiMe 3 ) 2 ) 2 yielded nacnac ZnN(SiMe 3 ) 2, 6a and 6b . From further reactions with 2-propanol nacnac ZnO i Pr, 7a and 7b, were obtained. Both complexes were catalytically active for polymerization of rac -lactide with apparent first-order rate constants of k app = 0.013−0.019 min −1 and 0.019−0.038 min −1 for 7a and 7b, respectively. Obtained polymers were highly heterotactic, with P r = 0.84−0.87 ( 7a ) and 0.65−0.71 ( 7b ). Analysis of remaining monomer after 75% conversion showed negligible ee and indicates that chiral 7a does not show enantioselectivity in rac -lactide polymerization. Complex 7a, but not 7b, catalyzes unselective transesterification of the polymer during and after polymerization. PLA microstructures in polymerizations with 7b were independent of temperature (23 or 0 °C) or monomer/catalyst ratio (100:1 to 400:1). However, slightly higher P r values were obtained in the presence of 10−100 equiv of MeCN or pyridine. Complexes nacnac Bn 2 Zn, 2b, 6b, and 7a were characterized by an X-ray diffraction study.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.004 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from it