Hydrogen Transfer from [MeB(C<sub>6</sub>F<sub>5</sub>)<sub>3</sub>]<sup>-</sup> to the Methyl Group of L<sub>2</sub>MMe<sup>+</sup> (M = Ti, Zr) as a Deactivation Pathway in Olefin Polymerization Catalysis: A Combined Quantum Mechanics and Molecular Mechanics Investigation
Bibliographic record
Abstract
A combined quantum-mechanical (QM) and molecular-mechanical (MM) model (QM/MM) has been used to investigate hydrogen transfer from the methyl group in [MeB(C 6 F 5 ) 3 ] - to the growing chain of a number of cationic single-site olefin polymerization catalysts. This reaction, which produces methane or higher alkanes, is a possible deactivation pathway in metal-catalyzed olefin polymerization. The cationic catalyst systems include (NPR 3 ) 2 TiR +, (Cp)(NPR 3 )TiR +, (Cp)(NCR 2 )TiR +, (Cp)(SiMe 2 NR)TiR +, and (Cp)(OSiR 3 )TiR + . For comparison, the corresponding zirconium catalyst systems have also been considered. We find hydrogen transfer to be more facile for titanium catalysts than for the corresponding zirconium systems. Furthermore, steric bulk and electron-donating ligands help to suppress hydrogen transfer. With R = CH 3, decomposition by hydride transfer is likely to take place for all the titanium catalysts at about 100 °C. However, for longer chains the decomposition temperature increases to 250 °C.
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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 | 0.002 | 0.001 |
| Meta-epidemiology (narrow) | 0.002 | 0.002 |
| Meta-epidemiology (broad) | 0.002 | 0.001 |
| Bibliometrics | 0.001 | 0.005 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 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; both teacher heads agree on what is shown here.
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".