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
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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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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| 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 it