Exploring the peri-, chemo-, and regioselectivity of addition of technetium metal oxides of the type TcO<sub>3</sub>L (L = Cl<sup>–</sup>, O<sup>–</sup>, OCH<sub>3</sub>, CH<sub>3</sub>) to substituted ketenes: a DFT computational study
Bibliographic record
Abstract
The addition of TcO3L (L = Cl, O–, OCH3, CH3) to substituted ketenes along various addition pathways was studied with density functional theory calculations to explore the peri-, chemo-, and regioselectivity of the reactions. In the reactions of TcO3L with dimethyl ketene, the results show that for L = O– and CH3, [1 + 1] addition to form a triplet zwitterionic intermediate is the preferred first step; for L = Cl, the [3 + 2]C=C addition across the O–Tc–Cl bond is the preferred first step and for L = OCH3 the [3 + 2]C=C addition across the O–Tc–OCH3 bond is the preferred first step. In the reactions of TcO3Cl with substituted ketenes, [1 + 1] addition to form a triplet zwitterionic intermediate is the preferred first step for X = Ph, CN, and Cl; the [3 + 2]C=C addition across the O–Tc–O bond of the complex is the preferred first step for X = H, while the [3 + 2]C=C addition across the O–Tc–CH3 bond is the preferred first step. Reactions involving a change in the oxidation state of metal have high activation barriers, while reactions that do not involve a change in oxidation state have low activation barriers. Reactions of ketenes with TcO3L complexes have lower activation barriers for the preferred addition pathways than those of the ReO3L complexes reported in the literature. Thus, the TcO3L complexes may be better catalysts for the activation of the C=C bonds of substituted ketenes than the reported ReO3L complexes.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| 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 source (direct Gemma or distilled Codex), 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".