Isolation of a Chromium Hydride Single-Component Ethylene Polymerization Catalyst
Bibliographic record
Abstract
Reaction of the divalent complex [( t -Bu)NPN( t -Bu)] 2 Cr ( 1 ) with different stoichiometric ratios of Al( i -Bu) 3 afforded {μ-[( t -Bu)NP( i -Bu)N( t -Bu)]Al( i -Bu) 2 } 2 Cr ( 2 ) and [{( i -Bu)P{μ-N( t -Bu)} 2 Al( i -Bu) 2 }Cr(μ-H)] 2 ( 3 ) as part of the same reaction sequence. Complex 2 arises from association of alane and the two ligands via alkylation of the P atom and retention of the AlR 2 unit. Complex 3 appears to be generated from subsequent dissociation of one alkylated ligand and possible transfer of an i -Bu group to Cr followed by β-H elimination or transfer of a hydride originating from isobutyl elimination of the aluminum-containing residue. Both species are potent ethylene polymerization catalysts with no need for further activation. It is assumed that 2 is transformed in situ into 3 under the influence of ethylene. Reactions with ethylene carried out in the presence of excess of Al( i -Bu) 3 switch the selectivity completely toward 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 | 0.001 |
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".