Zirconium Phosphinimide Complexes: Synthesis, Structure, and Deactivation Pathways in Ethylene Polymerization Catalysis
Bibliographic record
Abstract
Zirconium phosphinimide complexes of the form CpZr(NP- t -Bu 3 )Cl 2 ( 1 ) and Cp*Zr(NPR 3 )Cl 2 (R = i- Pr ( 2 ), t- Bu ( 3 )) were readily prepared under ambient conditions via the reaction of [CpZrCl 3 ] n or Cp*ZrCl 3 with the appropriate trialkylphosphinimide lithium salt (R 3 PNLi). A series of derivatives were readily obtained via alkylation or arylation of the above dihalide precursors. These included CpZr(NP- t -Bu 3 )Me 2 ( 4 ), Cp*Zr(NPR 3 )Me 2 (R = i- Pr ( 5 ), t -Bu ( 6 )), CpZr(NP- t -Bu 3 )Ph 2 ( 7 ), Cp*Zr(NPR 3 )Ph 2 (R = i -Pr ( 8 ), t -Bu ( 9 )), CpZr(NP- t -Bu 3 )Bn 2 ( 10 ), CpZr(NP- t -Bu 3 )(CH 2 SiMe 3 ) 2 ( 11 ), Cp*Zr(NPR 3 )(allyl) 2 (R = i -Pr ( 12 ), t -Bu (13 )), Cp*Zr(NPR 3 )(Cp)Cl (R = i -Pr ( 14 ), t -Bu ( 15 )), and Cp*Zr(NPR 3 )(CH 2 C(CH 3 )C(CH 3 )CH 2 ) (R = i- Pr ( 16 ), t -Bu ( 17 )). Reaction of 17 with the borane B(C 6 F 5 ) 3 yielded the zwitterionic and cationic complexes Cp*Zr(NP- t -Bu 3 )(CH 2 C(CH 3 )C(CH 3 )CH 2 B(C 6 F 5 ) 3 ) ( 18 ) and Cp*Zr(NP- t -Bu 3 )(THF)(CH 2 C(CH 3 )C(CH 3 )CH 2 B(C 6 F 5 ) 3 ) ( 19 ). A number of the above compounds were screened for their potential as catalyst precursors in ethylene polymerization. In general, upon activation with methylaluminoxane, the resulting catalysts exhibit low activity. Efforts to understand the deactivation pathway for these zirconium catalysts involved investigating the interactions of catalyst precursors with activators. For example, reaction of 4 with the borane B(C 6 F 5 ) 3 leads to aryl group transfer and formation of catalytically inactive CpZr(NP- t -Bu 3 )(C 6 F 5 ) 2 ( 20 ). Interactions with MAO were modeled via reaction with AlMe 3 . The Zr clusters (Cp*Zr) 4 (μ-Cl) 5 (Cl)(μ-CH) 2 ( 21 ) and (Cp*Zr) 5 (μ-Cl) 6 (μ-CH) 3 ( 22 ) were two of the products that were characterized from these reactions. The isolation of 21 and 22 infers that aryl for methyl exchange, ligand abstraction, and C−H bond activation may be catalyst deactivation pathways.
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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 | 0.001 |
| 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".