Ester Hydrogenation Catalyzed by a Ruthenium(II) Complex Bearing an N-Heterocyclic Carbene Tethered with an “NH<sub>2</sub>” Group and a DFT Study of the Proposed Bifunctional Mechanism
Bibliographic record
Abstract
A ruthenium(II) catalyst containing an NHC–amine (NHC = N-heterocyclic carbene) ligand (C–NH 2 ) catalyzes the H 2 -hydrogenation of various esters and lactones at 50 °C and 25 bar of H 2 pressure, mild reaction conditions compared with other reported catalysts. A maximum turnover frequency of 1510 h –1 for the hydrogenation of phthalide with a conversion of 96% is achieved in 4 h. DFT calculations suggest a concerted, asynchronous bifunctional mechanism for homogeneous ester hydrogenation; a proton transfer step from the N–H group of a ruthenium hydride-amine complex to the carbonyl group has the largest energy barrier in the catalytic cycle. A surprising observation is that methyl pivalate ( t BuCOOCH 3 ) is hydrogenated much more rapidly than is tert -butyl acetate (CH 3 COO t Bu). This is explained by the energetics of the rate-determining step of the proposed Ru–H/N–H bifunctional mechanism.
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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".