Understanding Ni(II)-Mediated C(sp<sup>3</sup>)–H Activation: Tertiary Ureas as Model Substrates
Bibliographic record
Abstract
We report a mechanistic study of C(sp 3 )–H bond activation mediated by nickel. Cyclometalated Ni(II) ureate [(PEt 3 )Ni(κ 3 - C,N,N -( C H 2 )N(Cy)(CO) N (( N )-quinolin-8-yl))] was synthesized and isolated from the urea precursor, (Me)(Cy)N(CO)N(H)(quinolin-8-yl), via C(sp 3 )–H activation. We investigated the effects of solvents and base additives on the rate of C–H activation. Kinetic isotope effect experiments showed that C–H activation is rate determining. Through deuterium labeling and protonation studies, we also showed that C–H activation can be reversible. We extended this reaction to a range of ureas with primary and secondary C(sp 3 )–H bonds, which activate readily to form analogous nickelated products. Finally, we showed that carboxylate additives assist with both ligand dissociation and initial N–H bond activation, consistent with a concerted metalation–deprotonation mechanism.
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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 | 0.000 |
| 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 | 0.001 |
| 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 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".