Multiple C−H Bond Activation: Reactions of Titanium−Phosphinimide Complexes with Trimethylaluminum
Bibliographic record
Abstract
Multiple C−H bond activation occurs upon reaction of phosphinimide complexes of the form Cp‘(R 3 PN)TiMe 2 (Cp‘ = Cp, indenyl; R = i- Pr, Cy, Ph) with excess AlMe 3, affording the carbide complexes Cp‘Ti(μ 2 -Me)(μ 2 -NPR 3 )(μ 4 -C)(AlMe 2 ) 3 or in some cases [CpTi(μ 2 -Me)(μ 2 -NPR 3 )(μ 5 -C)(AlMe 2 ) 3 ·(AlMe 3 )]. These species contain four- and five-coordinate carbide centers. VT-NMR studies established that such species exist in equilibrium. The four-coordinate carbide complexes retain Lewis acidity at a planar three-coordinate Al center, as evidenced by the reaction with diethyl ether, THF, or PMe 3 . This affords species of the form [CpTi(μ 2 -Me)(μ 2 -NPR 3 )(μ 4 -C)(AlMe 2 ) 2 (AlMe 2 (L))] (L = Et 2 O, THF, PMe 3 ). The Lewis acidity is also evidenced in the reaction of the carbide complexes with CpTi(NPR 3 )Me 2 . In this case, labeling studies affirm methyl group exchange processes. The analogous reactions of Cp(R 3 PN)Ti(CH 2 SiMe 3 ) 2 or Cp*(R 3 PN)TiMe 2 with AlMe 3 afforded CpTi(μ 2 -Me)(μ 2 -NPR 3 )(μ 3 -CSiMe 3 )(AlMe 2 ) 2 and Cp*Ti(μ 2 -Me)(μ 2 -NPR 3 )(μ 3 -CH)(AlMe 2 ) 2, respectively. These observations confirm that steric congestion can impinge on the C−H activation process. The nature of the above products of C−H bond activation was confirmed employing NMR, isotopic labeling, and crystallographic methods. The implications of these results with respect to C−H bond activation and polymerization catalysis are considered.
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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 | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 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".