Stability of Metal−Carbon Bond versus Metal Reduction during Ethylene Polymerization Promoted by a Vanadium Complex: The Role of the Aluminum Cocatalyst
Bibliographic record
Abstract
The dinuclear and trivalent complex {[(Me 3 Si)NCH 2 CH 2 ] 2 N(Me 3 Si)} 2 V 2 (μ-Cl) 2 ( 1 ) is the precursor to mono- and dinuclear alkyl derivatives that are thermally stable. For example, treatment with MeLi gives a stable methyl derivative, probably isostructural with 1, which upon further treatment with pyridine affords the mononuclear complex {[(Me 3 Si)NCH 2 CH 2 ] 2 N(Me 3 Si)}V(CH 3 )(pyridine) ( 2 ). However, reaction of 1 with Me 2 AlCl, AlMe 3, or PMAO-IP yields the tetrametallic species {[(Me 3 Si)NCH 2 CH 2 ] 2 N(Me 3 Si)} 2 V 2 (μ-Cl) 2 (AlMe 2 ) 2 ( 3 ), where the central core of 1 was preserved except for the vanadium centers, which were reduced to the divalent state. The two Me 2 Al residues remained coordinated to the amido ligand. The reduction of vanadium to the divalent state relates to the relatively short life of 1 as an ethylene polymerization catalyst. A similar reaction of 1 with AlCl 3 resulted in disproportionation forming the tetravalent complex {[(Me 3 Si)NCH 2 CH 2 ] 2 N(Me 3 Si)}VCl 2 AlCl 3 ( 4 ) and the pentanuclear mixed-valent V(II)/V(III) species [(AlCl 2 ){[(Me 3 Si)NCH 2 CH 2 ] 2 N(Me 3 Si)}V] 2 [(μ-Cl) 6 V]·(toluene) 2 ( 5 ). The fact that complex 5 contains a divalent vanadium atom stripped of its ligand system indicates that two different reaction mechanisms are operating to reduce the vanadium center and that the differing Lewis acidity of the two aluminum species is the determining factor.
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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 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.011 | 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".