Intermolecular Activation of Hydrocarbon C−H Bonds under Ambient Conditions by 16-Electron Neopentylidene and Benzyne Complexes of Molybdenum
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Bibliographic record
Abstract
CpMo(NO)(CH(2)CMe(3))(2) (1), a complex with alpha-agostic C-H.Mo interactions, evolves neopentane in neat hydrocarbon solutions at room temperature and forms the transient 16-electron alkylidene complex, CpMo(NO)(=CHCMe(3)), which subsequently activates solvent C-H bonds. Thus, it reacts with tetramethylsilane or mesitylene to form CpMo(NO)(CH(2)CMe(3))(CH(2)SiMe(3)) (2) or CpMo(NO)(CH(2)CMe(3))(eta(2)-CH(2)C(6)H(3)-3,5-Me(2)) (3), respectively, in nearly quantitative yields. Under identical conditions, 1 in p-xylene generates a mixture of sp(2) and sp(3) C-H bond activation products, namely CpMo(NO)(CH(2)CMe(3))(C(6)H(3)-2,5-Me(2)) (4, 73%) and CpMo(NO)(CH(2)CMe(3))(eta(2)-CH(2)C(6)H(4)-4-Me) (5, 27%). In benzene at room temperature, 1 transforms to a mixture of CpMo(NO)(CH(2)CMe(3))(C(6)H(5)) (6) and CpMo(NO)(C(6)H(5))(2) (7) in a sequential manner. Most interestingly, the thermal activation of 6 at ambient temperatures gives rise to two parallel modes of reactivity involving either the elimination of benzene and formation of CpMo(NO)(=CHCMe(3)) or the elimination of neopentane and formation of the benzyne complex, CpMo(NO)(eta(2)-C(6)H(4)). In pyridine, these intermediates are trapped as the isolable 18-electron adducts, CpMo(NO)(=CHCMe(3))(NC(5)H(5)) (8) and CpMo(NO)(eta(2)-C(6)H(4))(NC(5)H(5)) (9), and, in hydrocarbon solvents, they effect the intermolecular activation of aliphatic C-H bonds at room temperature to generate mixtures of neopentyl- and phenyl-containing derivatives. However, the distribution of products resulting from the hydrocarbon activations is dependent on the nature of the solvent, probably due to solvation effects and the presence of sigma- or pi-hydrocarbon complexes on the reaction coordinates of the alkylidene and the benzyne intermediates. The results of DFT calculations on these processes in the gas phase support the existence of such hydrocarbon complexes and indicate that better agreement with experimental observations is obtained when the actual neopentyl ligand rather than the simpler methyl ligand is used in the model complexes.
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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 | 0.000 |
| 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) | 0.001 | 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 it