Elementary Reactions at Organocopper(III): A Gas-Phase and Theoretical Study
Bibliographic record
Abstract
The role of copper(III) in copper-catalyzed coupling reactions is a topic of much debate in the literature, in large part due to the difficulty in isolating the typically reactive species. Advanced mass spectrometry experiments allow the isolation and interrogation of reactive species in the absence of any solvent, counterions, or competing species. Macrocyclic aryl-X-copper(III) complexes were isolated in the gas phase and subjected to collision-induced dissociation experiments to examine their unimolecular reactivity both qualitatively and quantitatively. When X = Cl or Br, the complexes fragment solely by deprotonation of nitrogen and concomitant loss of HX. The experimentally determined energies of activation are 33.4 ± 0.9 kcal mol –1 (X = Cl) and 35.8 ± 0.9 kcal mol –1 (X = Br). This process is analogous to nucleophile activation at a copper(III) center, and it is observed preferentially over C-X reductive elimination in the gas phase due to the strong ligating ability of the employed macrocyclic ligand. The measured activation energies for the observed nucleophile activation were used to test the performance of a range of popular DFT functionals for predicting reactivity at Cu III . Most dispersion-corrected functionals reproduced the experimental results with reasonable errors (D3bj-corrected TPSSh performed best), whereas the uncorrected values tended to significantly underestimate the activation energies. When X = I, a second fragmentation pathway becomes competitive, which involves loss of I • and reduction of copper from Cu III to Cu II . The relative energetics of one-electron versus two-electron processes at Cu III are discussed.
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
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".