Mechanistic Investigations of Phenoxyimine–Cobalt(II)-Catalyzed C(sp<sup>2</sup>)–C(sp<sup>3</sup>) Suzuki–Miyaura Cross-Coupling
Bibliographic record
Abstract
The mechanism of phenoxyimine (FI)−cobalt-catalyzed C(sp 2 )–C(sp 3 ) Suzuki–Miyaura cross-coupling was studied using a combination of kinetic measurements and catalytic and stoichiometric experiments. A series of dimeric (FI)cobalt(II) bromide complexes, [(4-CF 3 PhFI)CoBr] 2, [(4-OMePhFI)CoBr] 2, and [(2,6-di i PrPhFI)CoBr] 2, were isolated and characterized by 1 H and 19 F NMR spectroscopies, solution and solid-state magnetic susceptibility, electron paramagnetic resonance (EPR) spectroscopy, X-ray crystallography, and diffusion-ordered NMR spectroscopy (DOSY). One complex, [(4-CF 3 PhFI)CoBr] 2, was explored as a single-component precatalyst for C(sp 2 )–C(sp 3 ) Suzuki–Miyaura cross-coupling. Addition of potassium methoxide to [(4-CF 3 PhFI)CoBr] 2 generated the corresponding (FI)cobalt(II) methoxide complex as determined by 1 H and 19 F NMR and EPR spectroscopies. These spectroscopic signatures were used to identify this compound as the resting state during catalytic C(sp 2 )–C(sp 3 ) coupling. Variable time normalization analysis (VTNA) of in situ catalytic 19 F NMR spectroscopic data was used to establish an experimental rate law that was first-order in a (FI)cobalt(II) precatalyst, zeroth-order in the alkyl halide, and first-order in an activated potassium methoxide–aryl boronate complex. These findings are consistent with turnover-limiting transmetalation that occurs prior to activation of the alkyl bromide electrophile. The involvement of boronate intermediates in transmetalation was corroborated by Hammett studies of electronically differentiated aryl boronic esters. Together, a cobalt(II)/cobalt(III) catalytic cycle was proposed that proceeds through a “boronate”-type 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) | 0.001 | 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 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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".