Methane Loss from Cationic μ-Methyl Dimers Formed via Trityl Borate Activation of Monocyclopentadienyl Ketimide Complexes Cp[(<i><sup>t</sup></i>Bu)<sub>2</sub>CN]Ti(CH<sub>3</sub>)<sub>2</sub> (Cp = C<sub>5</sub>H<sub>5</sub>, C<sub>5</sub>Me<sub>5</sub>, C<sub>5</sub>Me<sub>4</sub>SiMe<sub>3</sub>)
Bibliographic record
Abstract
The reactions of the monocyclopentadienyl titanium dimethyl compounds Cp(L)TiMe 2 (L = t Bu 2 C N; Cp = C 5 H 5, 1a; C 5 Me 5, 1b; C 5 Me 4 SiMe 3, 1c ) with the trityl borate activator [Ph 3 C] + [B(C 6 F 5 ) 4 ] - are described. Formation of μ-methyl dimers of formula {[Cp(L)TiMe] 2 (μ-Me)} + [B(C 6 F 5 ) 4 ] - as a 1:1 mixture of rac and meso diastereomers is observed when 0.5 equiv of [Ph 3 C] + [B(C 6 F 5 ) 4 ] - is employed (−25 °C, C 6 D 5 Br; Cp = C 5 H 5, rac/meso 2a; C 5 Me 5, rac/meso 2b; C 5 Me 4 SiMe 3, rac/meso 2c ). Dynamic NMR and crossover experiments suggest that the dimers 2 are relatively nonlabile with respect to dissociation, intramolecular methyl group exchange, or diastereomer interconversion. Dimers 2 are observed to undergo methane loss in solution at room temperature, affording the new dimeric compounds 3a − c, {[Cp(L)Ti] 2 (μ-CH 2 )(μ-CH 3 )} + [B(C 6 F 5 ) 4 ] - . For the less sterically demanding C 5 H 5 ligand, 3a is formed as a mixture of rac/meso diastereomers (7:3), but for the bulkier C 5 Me 5 and C 5 Me 4 SiMe 3 ligands, the rac isomers of 3b and 3c are formed exclusively. In contrast to μ-methyl dimers 2, in which rac/meso interconversion is not observed, the diastereomers of 3 do undergo interchange, as determined by EXSY spectroscopy, and thus the rac/meso ratios observed are thermodynamic.
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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 | 0.011 | 0.007 |
| Meta-epidemiology (narrow) | 0.017 | 0.020 |
| Meta-epidemiology (broad) | 0.019 | 0.011 |
| Bibliometrics | 0.010 | 0.024 |
| Science and technology studies | 0.007 | 0.007 |
| Scholarly communication | 0.005 | 0.011 |
| Open science | 0.014 | 0.008 |
| Research integrity | 0.010 | 0.013 |
| Insufficient payload (model declined to judge) | 0.001 | 0.007 |
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".