Geminal Carbon–Hydrogen Bond Activation in Cumulenes Promoted by Adjacent Iridium/Ruthenium Centers
Bibliographic record
Abstract
The tetracarbonyl complex [IrRu(CO) 4 (dppm) 2 ][BF 4 ] (dppm = μ-Ph 2 PCH 2 PPh 2 ) ( 1 ) reacts with allene and methylallene, resulting in double, geminal carbon–hydrogen bond activation accompanied by H migration, one each to the β- and γ-carbons of the allene, yielding the vinylidene-bridged complexes [IrRu(CO) 4 (μ-C═C(H)R)(dppm) 2 ][BF 4 ] (R = CH 3 ( 2 ), C 2 H 5 ( 3 )). Reaction of 1 with 1,1-dimethylallene results in the activation of the pair of geminal C–H bonds together with one of the methyl C–H bonds, yielding the vinylvinylidene-bridged product [IrRu(CO) 4 (μ-C═C(H)C(CH 3 )═CH 2 )(dppm) 2 ][BF 4 ] ( 4 ), accompanied by H 2 loss. The addition of 1,1-difluoroallene to compound 1 does not lead to C–H activation but instead forms the fluoroallene-bridged adduct [IrRu(CO) 4 (μ-κ 1:κ 1 -F 2 C═ C – C H 2 )(dppm) 2 ][BF 4 ] ( 5 ), bound through the unsubstituted end of the allene and having the CH 2 group bound to Ru. This species rearranges, over 24 h at ambient temperature, to its isomer ( 5a ), having the CH 2 end bound to Ir. Although ethylene and propylene fail to react with 1 at ambient temperature, they react with the tricarbonyl analogue [IrRu(CO) 3 (dppm) 2 ][BF 4 ] ( 8 ) at −20 °C to yield the alkenyl-bridged hydrides [IrRu(CO) 3 (H)(μ-κ 1:η 2 -C(H)═CHR)(dppm) 2 ][BF 4 ] (R = H ( 6 ), CH 3 ( 7 )), by activation of a single C–H bond. Compound 8 reacts similarly with allene at −20 °C, yielding [IrRu(H)(CO) 3 (μ-κ 1:η 2 -CH═C═CH 2 )(dppm) 2 ][BF 4 ] ( 11 ). None of these alkenyl or allenyl hydride species give rise to a second C–H activation upon warming. However, warming 11 in the presence of CO does yield 2, together with decomposition products. Removal of a carbonyl from the vinylidene-bridged complexes [IrRu(CO) 4 (μ-C═C(H)R)(dppm) 2 ][BF 4 ] (R = CH 3 ( 2 ), R = H ( 9 )) generates the alkynyl hydride complexes [IrRu(H)(CO) 3 (μ-κ 1:η 2 -C≡CR)(dppm) 2 ][BF 4 ] (R = CH 3 ( 12 ), H ( 10 )), both of which can be converted back to the respective vinylidenes by CO addition. On the basis of these observations, a mechanism is proposed for the transformations of allene and methylallene into the methyl- and ethylvinylidene-bridged products, noted above.
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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".