Hydrogenolysis versus Methanolysis of First- and Second-Generation\nGrubbs Catalysts: Rates, Speciation, and Implications for Tandem Catalysis
Bibliographic record
Abstract
An unexpected “generation gap” is uncovered between\nthe Grubbs catalysts RuCl<sub>2</sub>(L)(PCy<sub>3</sub>)(CHPh)\n(<b>1a</b>, L = PCy<sub>3</sub>; <b>1b</b>, L = IMes, <i>N,N</i>′-bis(mesityl)imidazol-2-ylidene) in their reactions\nwith hydrogen versus methanol, in the presence of base. Treatment\nof the first-generation catalyst <b>1a</b> with H<sub>2</sub> and NEt<sub>3</sub> (CH<sub>2</sub>Cl<sub>2</sub>, 60 °C, 1000\npsi H<sub>2</sub>) affords RuHCl(H<sub>2</sub>)(PCy<sub>3</sub>)<sub>2</sub> (<b>2a</b>) in 75% yield within 30 min, as determined\nby in situ NMR analysis. Complex <b>2a</b> is in turn efficiently\nconverted (96%; 2 h) into the important hydrogenation catalyst RuHCl(CO)(PCy<sub>3</sub>)<sub>2</sub> (<b>3a</b>) by mild thermolysis with methanol\nand NEt<sub>3</sub> (4:1 CH<sub>2</sub>Cl<sub>2</sub>−MeOH,\n60 °C), 72% net yield for the <b>1a</b>−<b>3a</b> transformation. In comparison, subjecting the second-generation\ncatalyst <b>1b</b> to this two-step process effects <40%\nnet conversion to RuHCl(CO)(IMes)(PCy<sub>3</sub>) (<b>3b</b>) (hydrogenolysis of <b>1b</b>: ca. 60% RuHCl(H<sub>2</sub>)(IMes)(PCy<sub>3</sub>) (<b>2b</b>) (1 h); carbonylation of\nisolated <b>2b</b>: 65% <b>3b</b> (2.5 h)), owing to the\nsusceptibility of the dihydrogen derivative <b>2b</b> to disproportionation\nand decomposition. The opposite trend in efficiency for <b>1a</b> versus <b>1b</b> is found for methanolysis under argon in\nthe presence of base: <b>1b</b> undergoes 83% conversion to <b>3b</b>, versus <60% for the <b>1a</b>−<b>3a</b> transformation (4:1 CH<sub>2</sub>Cl<sub>2</sub>−MeOH, 60\n°C). This difference reflects the longer duration of the methanolysis\nreaction (8 h for <b>1a</b> vs 4 h for <b>1b</b>; cf.\n30 min and 1 h, respectively, for hydrogenolysis) and the lower thermal\nrobustness of <b>1a</b>. These findings highlight the importance\nof tailored, catalyst-specific approaches in devising efficient tandem\ncatalysis methodologies based on the first- and second-generation\nGrubbs complexes. They are directly relevant to the improved synthesis\nof advanced polymer materials via tandem ROMP−hydrogenation\nand potentially relevant to RCM- and CM-functionalization processes.
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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 | 0.003 |
| 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) | 0.051 | 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".