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 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) | 0.001 | 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) | 0.033 | 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 teacher head, 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".