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 machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| 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) | 0.002 | 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 source (direct Gemma or distilled Codex), 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".