Formation and Activation of Zr/Hf Bis(phenolate‐ether) Precatalysts
Bibliographic record
Abstract
Zr and Hf complexes of bis(phenolate‐ether) (“O4”) ligands feature high activity, stereoselectivity and molecular weight capability for propene polymerization at high temperature. Here we report a simplified ligand synthesis and several new examples of O4 ligands. The formation of precatalysts LMR2 (M = Zr, Hf; R = Bn, Me) from LH2 and MR4 was found to be accompanied in some cases by the formation of dimers (µ‐L)2[MR2]2, and X‐ray structures of two such dimers have been determined. Treatment of LMMe2 with [Ph3C]+[B(C6F5)4]– produces fairly clean cationic species LMMe+ which were studied by 1H NMR. 2D ROESY data, in particular, suggest that for “smaller” O4 ligands the LMMe+ cation reversibly rearranges from the active (fac/fac) form to a presumably inactive fac/mer or mer/mer form; more bulky substituents appear to suppress this rearrangement. Implications for polymerization catalysis are discussed.
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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".