α-Agostic Interactions and Growing Chain Orientation for Olefin Polymerization Catalysts
Bibliographic record
Abstract
Growing chain orientational preference is one of the key factors determining the stereoselectivity of olefin polymerization and related reactions such as carboalumination; α-agostic interactions are an important component of this preference. Using insertion of ethene in the M–CH 3 bond as a model, the intrinsic orientational preference was evaluated for a number of important catalyst types through determination of the energy profile for methyl group rotation at the insertion TS. Ti and Zr metallocenes show a pronounced preference (Ti, 10 kcal/mol; Zr, ∼6 kcal/mol) for a classical α-agostic arrangement with a single short M···CH contact and an elongated C–H bond; on CH 3 rotation the agostic elongation mostly disappears. In contrast, for all non-metallocene systems studied the orientational preference is much smaller or even opposite that of metallocenes. Moreover, on CH 3 rotation the agostic C–H bond elongation gets spread out over two C–H bonds rather than disappearing. These results point to greater chain orientation flexibility for non-metallocene catalysts.
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 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 | 0.000 | 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 teacher head, 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".