New Self-Activating Organochromium Catalyst Precursor for Selective Ethylene Trimerization.
Bibliographic record
Abstract
Two catalytic systems based on anionic ligands with the NPN structural motif, bearing tri- and pentavalent phosphorus, respectively, have been compared vis-à-vis their ability to selectively trimerize ethylene. In the case of the trivalent phosphorus ligands, reaction of the Cr(II) catalyst precursor [( t -Bu)NPN( t -Bu)] 2 Cr ( 1 ) with 2 equiv of MeLi afforded the Cr(III) species [( t -Bu)NP(Me)N( t -Bu)] 2 CrLi(OEt 2 ) ( 2 ). The same reaction with 3 equiv of MeLi yielded instead the Cr(II) species {[( t -Bu)NP(Me)N( t -Bu)]Cr(μ-Me)} 2 {Li(THF)} 2 ( 3 ). The P atoms of both 2 and 3 have been methylated. Activation of 2 and 3 with MAO produced an S-F distribution of oligomers. Conversely, activation of 3 with EtAlCl 2 exclusively afforded 1-hexene together with a small amount of polymer as a byproduct. Treatment of 2 with EtAlCl 2 did not yield an active catalyst. The reaction of CrCl 2 (THF) 2 with [( t- Bu)NP(Ph) 2 N( t -Bu)] − Li +, containing pentavalent phosphorus, afforded the Cr(II) derivative [( t- Bu)NP(Ph) 2 N( t- Bu)]Cr(μ-Cl) 2 Li(THF) 2 ( 4 ). Its alkylation with EtLi gave the ethyl-bridged dimer {[( t- Bu)NP(Ph) 2 N( t -Bu)]Cr(μ-Et)} 2 ( 5 ), which, upon thermolysis, afforded [( t- Bu)NP(Ph) 2 N( t -Bu)] 2 Cr ( 6 ). The structures of 5 and 3 are closely related, having in common two bridging alkyls and the same metal oxidation state but differing with respect to the P atom oxidation state and the presence/absence of alkali-metal cations. The catalytic behavior instead is remarkably different. Complex 5 is active as a self-activating selective ethylene trimerization catalyst, while complex 3 requires activation.
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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) | 0.001 | 0.001 |
| 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 | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.031 | 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".