Cationic Organoscandium β-Diketiminato Chemistry: Arene Exchange Kinetics in Solvent Separated Ion Pairs
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Bibliographic record
Abstract
Abstraction of methide from the beta-diketiminato supported organoscandium complex [L1ScMe2]2 using the trityl borate activator [Ph3C][B(C6F5)4] in arene solvents gives solvent separated ion pairs in which the arene (C6H5Br, 1a; C6H6, 1b; C7H8, 1c; 1,3,5-Me3C6H3, 1d) is coordinated to the cationic scandium center in an eta6 bonding mode. L1 incorporates methyl groups in the 2,4 positions of the ligand backbone and bulky 2,6-diisopropylphenyl groups on the nitrogen atoms. The relative binding strength of the arenes is C6H5Br < C6H6 < 1,3,5-Me3C6H3 < C7H8. Ion pairs 1a and 1c have been characterized crystallographically, and the C6H5Br derivative is notable for its eta6 bonding mode in preference to the more common eta1 bonding mode via the halogen atom. The kinetics of displacement of mesitylene by toluene (1d --> 1c) yield activation parameters of DeltaH = 21.4(6) kcal mol-1 and DeltaS = 6(1) cal mol-1 K-1. In combination with the observed lack of dependence of [toluene] on the rate of displacement, these data suggest a mechanism involving partial dissociation of the coordinated arene, followed by attack of the incoming arene. This chemistry has relevance to the role of these solvent separated ion pairs in olefin polymerization processes and presents a rare opportunity for the detailed study of these ephemeral species.
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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 | 0.001 |
| 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) | 0.004 | 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