The Impact of Oxygen on Leading and Emerging Ru-Carbene Catalysts for Olefin Metathesis: An Unanticipated Correlation Between Robustness and Metathesis Activity
Bibliographic record
Abstract
The impact of O 2 on olefin metathesis promoted by Ru-NHC and Ru-CAAC catalysts is examined (NHC = N-heterocyclic carbene; CAAC = cyclic alkyl amino carbene). An atmosphere of 8% O 2 in Ar is found to decrease turnover numbers by ca. 15–95% in ring-closing metathesis, including macrocyclization reactions. All H 2 IMes catalysts studied, irrespective of their ease of initiation, exhibit broadly similar O 2 -sensitivity, within the middle of this range. Much greater disparities in performance emerge for the CAAC catalysts, which exhibit an unexpected correlation between reactivity and robustness. Fast-initiating CAAC catalysts show greatest resistance to O 2 of all systems studied. Mechanistic studies with the second-generation Grubbs catalyst RuCl 2 (H 2 IMes)(PCy 3 )(=CHPh), which contains the useful PCy 3 and benzylidene reporter groups, suggest that [2 + 2] cycloaddition of O 2 dominates over the reported attack of O 2 at the benzylidene ligand. At catalyst concentrations compatible with NMR analysis (20 mM Ru), bimolecular coupling of Ru-4 is also a significant contributor to decomposition.
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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 | 0.001 | 0.001 |
| 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 | 0.001 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| 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".