Symmetry Aspects of H<sub>2</sub> Splitting by Five-Coordinate d<sup>6</sup> Ruthenium Amides, and Calculations on Acetophenone Hydrogenation, Ruthenium Alkoxide Formation, and Subsequent Hydrogenolysis in a Model <i>trans</i>-Ru(H)<sub>2</sub>(diamine)(diphosphine) System
Bibliographic record
Abstract
The potential energy surface (PES) of H(2) addition to the Ru═N bond of a model five-coordinate ruthenium amide (Ru═N), leading to an octahedral trans-Ru(H)(2)(diamine)(diphosphine) (HRu-NH) and subsequent acetophenone hydrogenation, is studied using M06 density functional theory methods. A qualitative molecular orbital analysis reveals that H(2) addition to the ground state of Ru═N (which has a distorted trigonal-bipyramidal geometry) fits the criterion of a symmetry-forbidden reaction. A transition state (TS) for H(2) heterolytic splitting by Ru═N corresponds to the reaction taking place on an excited state of the Ru═N having a square-pyramidal geometry and gives ΔG°(⧧) = 19.5 kcal/mol. The reaction between HRu-NH and acetophenone proceeds by a localized hydride-transfer TS with ΔG°(⧧) = 11.5 kcal/mol. This TS leads to an ion pair between a square-pyramidal d(6) ruthenium amino cation and the alkoxide and is uphill from the separated reactants by 3.5 kcal/mol. Subsequent abstraction of the amino proton by the alkoxide within the ion pair is barrierless, but it also lacks any thermodynamic driving force. In contrast, reorientation of the alkoxide within the ion pair to form an octahedral ruthenium alkoxide is calculated to be exoergic by 7.1 kcal/mol. These features of the PES suggest that the known rapid production of ruthenium alkoxides when stoichiometric amounts of acetophenone and HRu-NH are reacted at low temperatures proceeds by a simple direct route following hydride transfer. For the simplified model complex, ruthenium alkoxide is calculated to be the thermodynamic product of the hydrogenation reaction (exoergic by 3.6 kcal/mol). A TS for H(2) heterolytic splitting across the Ru-alkoxide bond is calculated to have ΔG°(⧧) (16.0 kcal/mol), slightly smaller than that of H(2) addition to the five-coordinate Ru═N.
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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) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.006 | 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".