Deactivation of Ruthenium Metathesis Catalysts via Facile Formation of Face-Bridged Dimers
Bibliographic record
Abstract
Reaction of RuCl(dcypb)(μ-Cl) 3 Ru(dcypb)(N 2 ) ( 3 ) with an excess of tert -butylacetylene at ambient temperatures yields the dinuclear monovinylidene RuCl(dcypb)(μ-Cl) 3 Ru(dcypb)(L) ( 4a; L = C CHBu t, dcypb = 1,4-bis(dicyclohexylphosphino)butane), rather than the expected mononuclear RuCl 2 (dcypb)(L). Attempted synthesis of an allenylidene derivative via the corresponding reaction with 1,1-diphenyl-2-propyn-1-ol stops at the stage of hydroxyvinylidene 4b (L = C CHC(OH)Ph 2 ). While formation of these dinuclear products may be an artifact of low solubility, the corresponding monoalkylidene species 4c (L = CHCH CMe 2 ) is obtained on treating soluble RuH(dcypb)(μ-Cl) 2 (μ-H)Ru(dcypb)(H 2 ) ( 5 ) with 3-methyl-3-chloro-1-butyne. Formation of the perchloro species 4c is consistent with facile homodimerization of the initially formed RuCl 2 (dcypb)(CHCH CMe 2 ) ( 2d ), with expulsion of one alkylidene ligand as the free carbene. 2,7-Dimethylocta-2,4,6-triene, the formal product of carbene coupling, is observed by 1 H NMR. A minor product in this synthesis is proposed to be RuCl(dcypb)(μ-Cl) 2 (μ 2,η 1 -CHCH CMe 2 )RuCl(dcypb) ( 8 ). While the low activity of 4a / 4b in ring-opening metathesis polymerization of norbornene is attributable to their low solubility, that of 4c points toward the stability of the Ru 2 (μ-Cl) 3 entity. The low activity and facile formation of 4c reveals an important deactivation pathway for catalysts of type 2d, with additional relevance to other such chlororuthenium complexes, including systems of the Grubbs type. Product identities were established by 1 H, 2 H, 13 C, and 31 P NMR and IR spectroscopy and (for 4c and 5 ) by X-ray crystallography.
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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 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".