N-heterocyclic carbenes bearing two, one and no nitrogen atoms at the ylidene carbon: insight from theoretical calculations
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Bibliographic record
Abstract
Electronic structure, thermodynamic stability and ligand properties in LRh(CO)2Cl complexes of a series of N-heterocyclic carbenes (NHCs) were studied at the DFT level. The systems under study are: imidazolin-2-ylidene (1), imidazolidin-2-ylidene (2), cyclic(alkyl)(amino)carbene (CAAC, 3), pyrazolin-3-ylidene (4), pyridin-2-ylidene (5), and pyridin-4-ylidene (6). The main structural feature influencing the properties of these species is the number of nitrogen atoms at the ylidene carbon. A decrease of the number of nitrogen atoms on the one hand leads to an increase in donor ability and ligand-to-metal bond strength, but lowers the stability of the NHC on the other hand. The number of nitrogen atoms can be taken as a key parameter for the classification of carbenes into 2N-NHC, 1N-NHC and r-NHC (r = remote).
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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 | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.005 | 0.000 |
Machine scores (provisional)
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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