Organoborane-Modified Silica Supports for Olefin Polymerization: Soluble Models for Metallocene Catalyst Deactivation
Bibliographic record
Abstract
Treatment of silsesquioxane 1 with 3.3 equiv of the reactive organoboranes 2 [(C 6 F 5 ) 2 BX; X = H or Cl] provides the novel, trifunctional organoborane 3, which was characterized by spectroscopic means and single-crystal X-ray crystallography. Compound 3 is an effective cocatalyst for ethylene polymerization in combination with Cp 2 ZrMe 2 but only when these two compounds are combined in situ, in the presence of monomer, suggesting limited stability of the putative ion-pair derived from these compounds. Reaction of 3 with Cp 2 ZrMe 2 in toluene solution leads to formation of MeB(C 6 F 5 ) 2 - and Cp 2 Zr-functionalized silsesquioxane 5 at room temperature. Monitoring of this reaction by NMR spectroscopy at low temperatures indicates that the only ion-pair present is [Cp 2 ZrMe][Me 2 B(C 6 F 5 ) 2 ] ( 4 ), which results from reaction of Cp 2 ZrMe 2 with the byproduct MeB(C 6 F 5 ) 2 . Formation of 4 is reversible under these conditions, while production of 5 (from 3 and Cp 2 ZrMe 2 ) is not; the latter process occurs at a rate that exceeds that observed for independent decomposition of 4 to form Me 2 B(C 6 F 5 ) and Cp 2 Zr(C 6 F 5 )Me. These studies suggest that the active polymerization catalyst generated in situ from 3 and Cp 2 ZrMe 2 is probably ion-pair 4 .
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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) | 0.002 | 0.001 |
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".