Aluminum Methyl and Chloro Complexes Bearing Monoanionic Aminephenolate Ligands: Synthesis, Characterization, and Use in Polymerizations
Bibliographic record
Abstract
A series of aluminum methyl and chloride complexes bearing 2( N -piperazinyl- N ′-methyl)-2-methylene-4-R′-6-R-phenolate or 2( N -morpholinyl)-2-methylene-4-R′-6-R-phenolate ([ONE R1,R2 ]-) {[R 1 = t Bu, R 2 = Me, E = NMe ( L1 ); R 1 = R 2 = t Bu, E = NMe ( L2 ); R 1 = R 2 = t Bu, E = O ( L3 )} ligands were synthesized and characterized through elemental analysis, 1 H, 13 C{ 1 H}, and 27 Al NMR spectroscopy, and X-ray crystallography. Reactions of AlMe 3 with two equivalents of L1 H- L3 H gave {[ONE R1,R2 ] 2 AlMe} ( 1 – 3 ), while reaction of Et 2 AlCl with two equivalents of L1 H and L3 H afforded {[ONE R1,R2 ] 2 AlCl} ( 4 and 5 ) as monometallic complexes. The catalytic activity of complexes 1 – 3 toward ring-opening polymerization (ROP) of ε-caprolactone was assessed. These complexes are more active than analogous Zn complexes for this reaction but less active than the Zn analogues for ROP of rac -lactide. Characteristics of the polymer as well as polymerization kinetics and mechanism were studied. Polymer end-group analyses were achieved using 1 H NMR spectroscopy and MALDI-TOF MS. Eyring analyses were performed, and the activation energies for the reactions were determined, which were significantly lower for 1 and 2 compared with 3 . This could be for several reasons: (1) the methylamine (NMe) group of 1 and 2, which is a stronger base than the ether (O) group of 3, might activate the incoming monomer via noncovalent interactions, and/or (2) the ether group is able to temporarily coordinate to the metal center and blocks the vacant coordination site toward incoming monomer, while the amine cannot do this. Preliminary studies using 4 and 5 toward copolymerization of cyclohexene oxide with carbon dioxide have been performed. 4 was inactive and 5 afforded polyether carbonate (66.7% epoxide conversion, polymer contains 54.0% carbonate linkages).
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| 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 source (direct Gemma or distilled Codex), 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".