Electronic Directing Group Modification for Improved Ni(II)-Mediated C(sp<sup>3</sup>)–H Activation: A Hammett Investigation of 8-Aminoquinoline
Bibliographic record
Abstract
The 8-aminoquinoline (AQ) directing group has received considerable attention for facilitating superior C–H bond activation in unactivated substrates compared to other N, N -bidentate directing groups. However, for nickel, the role of AQ in C–H activation reactions has not been fully realized as of yet. Kinetic experiments and a Hammett analysis of 5-substituted AQs in C(sp 3 )–H activation have uncovered a disconnected trend between electron-rich and electron-poor substituted AQs that yield a nonlinear Hammett plot in the Ni(II)-mediated C(sp 3 )–H activation of tertiary ureas. We have identified and synthesized paramagnetic tris -AQ ligated anionic Ni(II) species, such as Na[ fac -( 1d – ) 3 Ni] (complex 5 ). We propose that paramagnetic complexes participate in a pre-equilibrium with the active species that undergoes C–H activation. We hypothesize that these coordinatively saturated paramagnetic tris -ureate complexes are favored for electron-withdrawing directing groups, subsequently influencing the initial rates of C–H activation. These observations also point toward the importance of catalyst speciation and the role of ligand electronic properties, not just steric features that result in speciation changes and subsequent changes in reaction rates in Ni catalysis.
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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 | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.002 |
| 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".