Switchable Chromium(II) Complexes of a Chelating Amidophosphine (N−P) for Selective and Nonselective Ethylene Oligomerization
Bibliographic record
Abstract
Treatment of the lithium salt of t -BuN(H)PPh 2 in THF with CrCl 2 ·(THF) 2 afforded a dinuclear, [( t -BuNPPh 2 )Cr 2 (μ- t -BuNPPh 2 ) 3 ]·(toluene) 1.5 ( 1 ), and a tetrameric cluster, [( t -BuNPPh 2 )Cr(μ- t -BuNPPh 2 ) 2 Cr(μ-Cl)] 2 ·(toluene) 2 ( 5 ), depending on the reagents' stoichiometric ratio. Complex 1 is dimeric with a long intermetallic distance and the ligands adopting an asymmetric and distorted bridging-chelating bonding mode. Complex 5 is instead a symmetry-generated tetramer with two identical dimetallic units, each closely related in geometry to 1, linked by two bridging chlorine atoms. The reactions of 1 with alkyl aluminum activators afforded a series of divalent complexes, [{(μ-AlMe 3 )( t -BuNPPh 2 )} 2 Cr]·(toluene) ( 2 ), [{(μ-AlMe 2 Cl)( t -BuNPPh 2 )} 2 Cr]·(toluene) ( 3 ), and [{(μ-AlEt 2 Cl)( t -BuNPPh 2 )} 2 Cr]·(toluene) ( 4 ), containing organo-aluminum residues. Similarly, reaction of 5 with AlMe 3 gave [{(μ-AlMe 2 )( t -BuNPPh 2 ) 2 }Cr(μ-Cl)] 2 ·(toluene) 1.9 ( 6 ), also characterized by an X-ray crystal structure. Finally, the trivalent complex [( t -BuNPPh 2 ) 3 Cr] ( 7 ) was readily prepared via reaction of the lithiated ligand with CrCl 3 (THF) 3 . Upon treatment with AlMe 3 or Et 2 AlCl, complexes 2 and [{(μ-AlEtCl 2 )( t -BuNPPh 2 )} 2 Cr]·(toluene) ( 8 ) were isolated and fully characterized. In turn, this indicated that reduction to the divalent state is the primary stage of the activation process of the trivalent species. The catalytic behavior of all of these complexes has been assessed in the presence and absence of cocatalyst and with different solvents. The result showed a pronounced solvent effect, allowing switching from nonselective oligomerization to selective trimerization.
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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) | 0.001 | 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".