A Combined Experimental and Computational Study of Unexpected C−F Bond Activation Intermediates and Selectivity in the Reaction of Pentafluorobenzene with a (PEt<sub>3</sub>)<sub>2</sub>Ni Synthon
Bibliographic record
Abstract
The reaction of the anthracene adduct (PEt 3 ) 2 Ni(η 2 -C 14 H 10 ) with C 6 F 5 H or C 6 F 6 provides a facile route to the isolable dinuclear adducts [(PEt 3 ) 2 Ni] 2 (μ-η 2:η 2 -C 6 F 5 H) and [(PEt 3 ) 2 Ni] 2 (μ-η 2:η 2 -C 6 F 6 ). The Ni(PEt 3 ) 2 moieties reside on opposite faces of the fluoroarene ring, and bond lengths indicate considerable loss of aromaticity. Solutions of [(PEt 3 ) 2 Ni] 2 (μ-η 2:η 2 -C 6 F 5 H) with added C 6 F 5 H convert with >97% selectivity to the ortho -F activated compound tran s-(PEt 3 ) 2 NiF(2,3,4,5-C 6 F 4 H). The addition of C 6 F 5 H to solutions of [(PEt 3 ) 2 Ni] 2 (μ-η 2:η 2 -C 6 F 5 H) also provided equilibrium amounts of the mononuclear complex (PEt 3 ) 2 Ni(η 2 -C 6 F 5 H) and the C−H activation product trans- (PEt 3 ) 2 NiH(C 6 F 5 ) as intermediates. Increased C 6 F 5 H concentrations accelerate the rate of C−F bond activation. The reaction of (PEt 3 ) 4 Ni with C 6 F 5 H under similar conditions also provided spectroscopic evidence for the presence of the binuclear adduct [(PEt 3 ) 2 Ni] 2 (μ-η 2:η 2 -C 6 F 5 H), the mononuclear adduct (PEt 3 ) 2 Ni(η 2 -C 6 F 5 H), and the C−H activation product trans- (PEt 3 ) 2 NiH(C 6 F 5 ) in the reaction mixture; however, unlike the C−F bond activation observed from pure [(PEt 3 ) 2 Ni] 2 (μ-η 2:η 2 -C 6 F 5 H) and C 6 F 5 H, the reaction of Ni(PEt 3 ) 4 and C 6 F 5 H yields a mixture of C−F activation products that included the para -F and meta -F activation products as major products. This indicates that alternate mechanisms of C−F activation dominate with this source of the Ni(PEt 3 ) 2 moiety under these conditions, suggestive of a radical mechanism. Density functional theory calculations were carried out to provide insight into the 19 F NMR spectra of these complexes, as well as to gain understanding of the importance of phosphine donor choice in the thermodynamics of the interconversion of the dinuclear complexes, mononuclear complexes, and C−H activation products.
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| 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) | 0.000 | 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".