Complex Speciation of bipy- and phen-NNP Pincer Complexes of Ruthenium under Catalytic Ester Reduction Conditions
Bibliographic record
Abstract
The N -heterocyclic backbone of NNP pincer ligands derived from 2,2′-bipyridine and 1,10-phenanthroline is prone to hydrogenation under H 2 or in alcohols. The new complex of this work, RuHCl(CO)[phen-NNP] ( 4 ), where phen-NNP = 2-((di- t -butylphosphaneyl)methyl)-1,10-phenanthroline, undergoes dearomatization when treated with potassium tert-butoxide. The dearomatized product 5 reacts with ethanol and dihydrogen to give 16-electron hydrides 7 – 9 containing partially hydrogenated phen-NNP ligands. The structure and reactivity of complexes 5 – 9 are detailed in the present report. Similar chemical behavior has been documented for the Milstein catalyst, RuHCl(CO)[bipy-NNP] where bipy = 6-((di- t -butylphosphaneyl)methyl)-2,2′-bipyridine. The dearomatized Milstein catalyst ( 1 ) is readily hydrogenated in solution at room temperature to give the main product 2 containing an NNP ligand with the central piperidine fragment, accompanied by the dimer 3 possessing one NNP ligand with an outer piperidine fragment. The dearomatized bipy- and phen-NNP complexes 1 and 5 and their hydrogenated derivatives 2, 3, and 9 were tested in this work in solventless room-temperature reduction of methyl hexanoate to hexanol under 50 bar H 2 while using a 5000:1 substrate-to-catalyst ratio. The phen-NNP derived complexes 5 and 9 proved inactive in this reaction. The density functional theory (DFT) calculations indicated that H 2 addition to the 16-electron 9 should be endoergic by at least 8.5 kcal/mol, thus, making the complex unable to transfer H 2 to the substrate. With the Milstein catalyst 1 and its hydrogenated derivatives 2 and 3 the order of activity in room-temperature reduction of methyl hexanoate was 3 > 1 > 2 with the conversions reaching 99, 70, and 34%, respectively. A distinct induction period observed in this reaction with 1 suggested that the catalytic activity should be attributed to a highly active complex catalyst formed from 1 in the reaction solution. A possible structure for this “super-catalyst” is proposed.
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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 | 0.000 | 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 | 0.000 |
| 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 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".