Highly active and thermostable camphyl α‐diimine–nickel(II) catalysts for ethylene polymerization: Effects of <i>N</i>‐aryl substituting groups on catalytic properties and branching structures of polyethylene
Bibliographic record
Abstract
A group of nickel bromide complexes containing the rigid bidentate bis(arylimino)camphane ligands (Ar‐BIC) with different N ‐aryl substituents, [ArN═C(camphyl)C(camphyl)═NAr]NiBr 2 (Aryl = 2,6‐Me 2 C 6 H 3 [ Ni1 ], 2,4‐Me 2 C 6 H 3 [ Ni2 ], 2,4,6‐Me 3 C 6 H 2 [ Ni3 ], 2,6‐Me 2 ‐4‐{(C 6 H 4 F) 2 CH}‐C 6 H 2 [ Ni4 ], 2,4‐Me 2 ‐6‐{(C 6 H 4 F) 2 CH}‐C 6 H 2 [ Ni5 , with the corresponding ligand as L5 ], and 2‐Me‐4,6‐{(C 6 H 4 F) 2 CH} 2 ‐C 6 H 2 [ Ni6 ]), has been synthesized and characterized. The molecular structures of L5 , Ni1 , Ni3 , Ni4 , and Ni6 were elucidated with single‐crystal X‐ray diffraction. The nickel centers displayed a four‐coordinate geometry that can be best described as a distorted tetrahedral geometry. Upon treatment with either MMAO or Me 2 AlCl, Ni1 – Ni6 showed moderate to high activities for ethylene polymerization, producing polyethylenes (PEs) with low to high molecular weights (0.02–23.7 × 10 5 g mol −1 ) and low polydispersity indices (PDI: 1.6–2.6). In comparison with reference nickel precatalysts ligated by bis(arylimino)acenaphthene (Ar‐BIAN) and bis(arylimino)butane (Ar‐BIB), the title complexes displayed much better thermal stability and higher catalytic activities (up to 11.2 × 10 6 g PE (mol Ni) −1 h −1 at 70°C), delivering polyethylenes with higher molecular weights. All the resultant polyethylenes are moderately to highly branched with the branching content and type of branching strongly affected by the type of N ‐aryl substituting groups. Notably, the polymers produced with ortho ‐hydrogen Ni2 /Me 2 AlCl possessed the highest branching density and unique terminal vinyl (CH═CH 2 ) and internal vinylene (CH═CH) structure. On the other hand, ortho ‐di( p ‐fluorophenyl)methyl‐containing Ni5 and Ni6 just gave 30 and 19 branches per 1000 Cs due to the reduced chain walking capability as a result of the bulkier substituting groups.
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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) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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".