Zirconium Complexes of a Rigid, Dianionic Pincer Ligand: Alkyl Cations, Arene Coordination, and Ethylene Polymerization
Bibliographic record
Abstract
Reaction of 4,5-bis(2,4,6-triisopropylanilino)-2,7-di- tert -butyl-9,9-dimethylxanthene (H 2 XN 2 ) with [Zr(NMe 2 ) 4 ], followed by crystallization from O(SiMe 3 ) 2, yielded [(XN 2 )Zr(NMe 2 ) 2 ]·{O(SiMe 3 ) 2 } 0.5 ( 1 ·{O(SiMe 3 ) 2 } 0.5 ). The zirconium dimethyl complex [(XN 2 )ZrMe 2 ] ( 2 ) was subsequently accessed (a) by treatment of 1 ·(O(SiMe 3 ) 2 ) 0.5 with excess AlMe 3 or (b) via reaction of 1 ·(O(SiMe 3 ) 2 ) 0.5 with excess Me 3 SiCl, affording [(XN 2 )ZrCl 2 ] ( 3 ) followed by reaction of 3 with 2 equiv of MeLi. Reaction of [(XN 2 )ZrMe 2 ] ( 2 ) with one equiv of B(C 6 F 5 ) 3 or [CPh 3 ][B(C 6 F 5 ) 4 ] yielded cationic [(XN 2 )ZrMe][MeB(C 6 F 5 ) 3 ] ( 4 ) and [(XN 2 )ZrMe(arene)][B(C 6 F 5 ) 4 ] {arene = η 6 -benzene ( 5a ), η 6 -toluene ( 5b ), or bromobenzene ( 5c )}, respectively. Both 4 and 5b are active for ethylene polymerization under 1 atm of ethylene at 24 and 80 °C in toluene with activities ranging from 23.5–883 kg mol –1 atm –1 h –1, yielding polymers with weight-average molecular weights ( M w ) of 70,800–88,100 g mol –1 and polydispersities ( M w / M n ) of 3.94–4.67.
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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 | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.006 | 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".