Morpholine-Stabilized Cationic Aluminum Complexes and Their Reactivity in Ring-Opening Polymerization of ε-Caprolactone
Bibliographic record
Abstract
The first structures exhibiting bidentate (N, O) chelation of a morpholine group to a p-block element (aluminum) have been prepared and characterized by X-ray diffraction methods: Al[ L ] + [WCA] −, where [ L ] = 4-(2-aminoethyl)morpholinylamino- N, N -bis(2-methylene-4,6- tert -butylphenolate) and [WCA] − is a weakly coordinating anion. These compounds are easily synthesized by reacting Al[ L ]Cl with an equimolar amount of anhydrous Lewis acid and were characterized by elemental analyses, ESI–MS, MALDI–TOF MS, 1 H, 13 C{ 1 H}, and multinuclear NMR spectroscopy. DFT calculations showed that Al[ L ] + cations containing bidentate NO coordination of the morpholine group are at least 21.1 kJ/mol more stable when compared to hypothetical monodentate (N bound) structures. When combined with protic co-initiators (EtOH, glycerol carbonate), the cationic complexes, where [WCA] − = [GaCl 4 ] − or [InCl 4 ] −, are living catalyst systems for the polymerization of ε-caprolactone, producing polycaprolactone with narrow dispersity ( D̵ = 1.00–1.05). Employing glycidol as a co-initiator furnished polymers with narrow dispersity ( D̵ = 1.01–1.07) but experimental molecular weights diverged considerably from the calculated values. Similar reactivity toward ROP was observed for all complexes containing a stable [WCA] − but where [WCA] − = [AlCl 4 ] −, upon combination with alcohols, alcoholysis was observed. Kinetic studies (Eyring analyses) allowed the determination of activation parameters, which were consistent with a coordination–insertion mechanism for the catalysts containing [WCA] − = [GaCl 4 ] − or [InCl 4 ] − . End group analyses using MALDI–TOF mass spectrometry and 1 H NMR spectroscopy showed hydroxyl and ester end groups within the polymer, corroborating the proposed mechanism. Stoichiometric reactions of EtOH, glycidol or tert -butyl alcohol with the complex, where [WCA] − = [GaCl 4 ] −, showed protonation of the ligand at the N -morpholine site, which leads to dissociation of this pendent group.
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How this classification was reachedexpand
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) | 0.001 | 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 itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".