Toward the Identification of Dormant and Active Species in MAO (Methylaluminoxane)-Activated, Dimethylzirconocene-Catalyzed Olefin Polymerization
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Bibliographic record
Abstract
Possible structural candidates for the active ( III ) and dormant ( IV ) species in dimethylzirconocene-catalyzed, MAO (methylaluminoxane)-activated olefin polymerization have been studied via density functional theory (DFT). These species are [Cp 2 ZrMeAlMe 3 ] + [MeMAO] - ( III ) and [Cp 2 ZrMe] + [MeMAO] - ( IV ), respectively, where Me = CH 3 and Cp = n 5 -C 5 H 5 . Relative energies in gas phase and toluene solution as well as 1 H and 13 C NMR chemical shifts have been calculated. These chemical shifts have been compared with 1 H and 13 C NMR data from new experimental investigations studying the interaction between Cp 2 ZrMe 2 and MAO in toluene solution. 1 By combining experimental and theoretical results, we have been able to identify the most likely candidates for both the dormant and active species. Moreover, we are able to predict that an Al/Zr ratio of ∼275:1 at 298.15 K is necessary in order for all of the Cp 2 ZrMe 2 to bind to MAO as the structures we propose for III and IV . This ratio corresponds to the disappearance of the following species from solution: free Cp 2 ZrMe 2, the weak complex of Cp 2 ZrMe 2 and MAO ( I ), and [Cp 2 ZrMe(μ-Me) Cp 2 ZrMe] + [MeMAO] - ( II ). Such a mixture would have a IV / III ratio of ∼1.8:1.
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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 | 0.001 |
| 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) | 0.006 | 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 it