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 O2 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% O2 in Ar is found to decrease turnover numbers by ca. 15–95% in ring-closing metathesis, including macrocyclization reactions. All H2IMes catalysts studied, irrespective of their ease of initiation, exhibit broadly similar O2-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 O2 of all systems studied. Mechanistic studies with the second-generation Grubbs catalyst RuCl2(H2IMes)(PCy3)(=CHPh), which contains the useful PCy3 and benzylidene reporter groups, suggest that [2 + 2] cycloaddition of O2 dominates over the reported attack of O2 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 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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 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) | 0.000 | 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".