Outer sphere hydrogenation of ketones catalyzed by ruthenium(II) hydride complexes
Bibliographic record
Abstract
The results of mechanistic and kinetic studies on Noyori-type catalytic systems for the hydrogenation of ketones are presented. The systems consist of a chlorohydrido precatalyst RuHCl(P2)(H2N cap;N) (P2 = binap, bis(phosphaadamantyl)propane, and R, R-dppdpen or bis-triphenylphosphine; H2N cap;N = R, R-dach, tmen, ampy or appH), a strong base and hydrogen gas. The active catalysts are proposed to be the dihydrides trans-Ru(H) 2(P2)(H2N cap;N) and the hydrido-amido complexes RuH(P2)(HN cap;N). The amido complexes are 5 coordinate species containing a formally Ru=N double bond as confirmed by X-ray structural analysis. Both groups of complexes are the active catalysts for ketone hydrogenation under mild conditions without a base present. In the cases when the diamines do not contain hydrogen atoms on the carbon alpha to the nitrogen donor, the amido complexes are stable enough to be isolated. Otherwise they are prone to beta-hydride elimination giving complex mixtures of products. The trans dihydride geometry is stabilized using rigid chelating diphosphines (binap) and diamines (tmen) that prevent the isomerization to cis-dihydride species. These cis dihydrides are obtained in the systems containing two triphenylphosphine and the chelating nitrogen donors (R, R-dach, ampy). The cis dihydrides are the catalyst precursors only if the two phosphine ligands are also mutually cis. The complexes of cis-dihydride trans phosphine geometry are catalytically inactive. The replacement of an NH2 group on a diamine with a pyridyl group leads to more active (pre)catalysts for the ketone hydrogenation. The substitution of both NH2 groups with pyridyl groups renders the complexes inactive. The kinetic studies revealed that the diamine complexes follow the rate law rate=k[H2][Ru] where k is the rate constant, [H2] and [Ru] are dihydrogen and catalyst concentrations respectively. The slow step of the catalytic cycle is the heterolytic splitting of H 2 molecule over the Ru=N bond of the amido complex. The transfer of a hydride from Ru and a proton from an NH2 group to the C=O group on a substrate is a facile step. For the complexes containing H2N cap;py ligands (one NH2 group in diamine replaced with py group), the kinetic study revealed a more complex mechanism in which the product alcohol is involved in an autocatalytic manner.
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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".