Switchable Chromium(II) Ethylene Oligomerization/Polymerization Catalyst
Bibliographic record
Abstract
The tri- and divalent chromium derivatives of [N-Me,tripyrr] ([N-Me,tripyrr] = 2,5-bis(diphenyl(pyrrol-2-yl)methyl)-1-methylpyrrole) [N-Me,tripyrr]CrCl ( 1 ), and [N-Me,tripyrr]Cr(L) 2 ·(THF) 0.5 ( 2 ) [L = THF ( 2a ), pyridine ( 2b )] were obtained in good yield from the reaction of the dipotassium salt of the ligand with CrCl 3 (THF) 3 and CrCl 2 (THF) 2, respectively. Reaction of the dilithium salt of the ligand with CrCl 2 (THF) 2 led to the divalent analogue [N-Me,tripyrr]Cr(μ-Cl)Li(THF) 3 ( 3 ), wherein a Li−Cl unit was retained by the metal center. The compounds were tested for ethylene oligomerization activity upon activation with two different alumoxanes. In the case of MAO, the Cr(II) catalyst precursors 2b and 3 showed a marked increase in activity with respect to the trivalent 1 . The product distributions from compounds 1 and 2b were nearly identical, indicating that the Cr(II) oxidation state provides better catalyst precursors. Use of the i-BuAlO activator instead of MAO afforded exclusively polymerization with high activity and produced linear, low molecular weight polyethylene.
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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".