Influence of the Counterion MeB(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub><sup>-</sup> and Solvent Effects on Ethylene Polymerization Catalyzed by [(CpSiMe<sub>2</sub>NR)TiMe]<sup>+</sup>: A Combined Density Functional Theory and Molecular Mechanism Study
Bibliographic record
Abstract
A combined density functional theory and molecular mechanism (QM/MM) method has been used to study the first (R = Me) and the second (R = propyl) insertion of the ethylene monomer into the Ti−R bond of (CpSiMe 2 N t Bu)(R)Ti-μ-MeB(C 6 F 5 ) 3 . The present extensive theoretical investigation provides a comprehensive analysis of the chain propagation process for ethylene polymerization catalyzed by CGC in the presence of the counterion MeB(C 6 F 5 ) 3 - . Both the counterion and solvent effects play important roles in the first and second ethylene propagations and therefore cannot be ignored in the mechanistic study. The influence of the counterion and the solvent not only changes the reaction barriers but also alters the rate-determining step for the chain propagation, from insertion to uptake. The cis approach is preferred over the trans approach for the second ethylene propagation in the gas phase as well as in solution. The total reaction barrier for the first ethylene propagation has been calculated to be slightly higher than that for the second ethylene propagation, in general agreement with experimental findings. The total barriers in solution are 11.7 and 8.5 kcal/mol for the first and second ethylene propagations, respectively. These barriers are comparable to the activation energy (13.3 kcal/mol) found experimentally for the same catalyst (CGC).
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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 | 0.000 |
| 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 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".