Mechanism of Formation of [(PMe<sub>3</sub>)<sub>3</sub>Rh(−C⋮C−R)<sub>2</sub>(H)] via C−H Oxidative Addition: Isomerization, Alkyne Exchange, and Hydride Replacement
Bibliographic record
Abstract
The mechanism of formation of mer,trans -[(PMe 3 ) 3 Rh(−C⋮C−R) 2 H] from [(PMe 3 ) 4 Rh(Me)] and terminal alkyne has been studied. The initial step of the reaction is the elimination of methane and the formation of the trigonal bipyramidal complex [(PMe 3 ) 4 Rh(−C⋮C−R)], a reaction that is complete in time of mixing at −78 °C. This intermediate undergoes an oxidative addition reaction with a second equivalent of alkyne to give fac -[(PMe 3 ) 3 Rh(−C⋮C−R) 2 H] as the kinetic product. This fac isomer is not stable above −20 °C and isomerizes to the thermodynamic product mer,trans -[(PMe 3 ) 3 Rh(−C⋮C−R) 2 H]. fac -[(PMe 3 ) 3 Rh(−C⋮C−R) 2 H] will exchange alkynyl groups with free alkyne, a reaction that has a lower energetic barrier than the isomerization to mer,trans -[(PMe 3 ) 3 Rh(−C⋮C−R) 2 H]. Density functional theory studies on all stages of the formation of mer,trans -[(PMe 3 ) 3 Rh(−C⋮C−R) 2 H] have been carried out and give ground state energies in line with those experimentally observed. Once formed, mer,trans -[(PMe 3 ) 3 Rh(−C⋮C−R) 2 H] is configurationally stable and not prone to scrambling, although it will react with chloroform, whereupon the hydride is replaced by chloride. The initial product of this reaction is mer,trans -[(PMe 3 ) 3 Rh(−C⋮C−R) 2 Cl], and this compound has been studied by single-crystal X-ray diffraction. In solution mer,trans -[(PMe 3 ) 3 Rh(−C⋮C−R) 2 Cl] isomerizes slowly to mer,cis -[(PMe 3 ) 3 Rh(−C⋮C−R) 2 Cl].
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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 | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.002 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.004 | 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".