A Combined Density Functional and Molecular Dynamics Study on Ethylene Insertion into the Cp<sub>2</sub>ZrEt−MeB(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub> Ion-Pair
Bibliographic record
Abstract
Several aspects related to the insertion process of an ethylene molecule into the Zr−ethyl (Et) bond of the Cp 2 ZrEt−MeB(C 6 F 5 ) 3 contact ion-pair were examined by static density functional and first-principles molecular dynamic methods. The most stable conformer of this contact ion-pair can be described as having the anion coordinated to the Zr on the backside of the ethyl chain via a methyl bridge. This most stable conformation of Cp 2 ZrEt−MeB(C 6 F 5 ) 3 contained no agostic interactions with any of the hydrogen atoms on the ethyl chain. The insertion pathway studied considers the ethylene to approach the metal center of the contact ion-pair from the side opposite the anion. The ethyl chain rotates away from the olefin and the anion was pushed out of the coordination sphere of the zirconium before complexation occurs. The insertion occurs rapidly and apparently without significant barrier after successful complexation of the olefin. The behavior of the counterion after insertion was also examined. Considerations were given to an associative mechanism in which the counterion recombines with the catalyst to form a new contact ion-pair. Also considered was a dissociative mechanism in which the counterion continues to detach from the cation via the formation of an olefin-separated ion-pair. Either mechanism is a possibility depending on the conditions under which the polymerization is carried out.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 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".