Characterization of Intermediates in the C−F Activation of Tetrafluorobenzenes using a Reactive Ni(PEt<sub>3</sub>)<sub>2</sub>Synthon: Combined Computational and Experimental Investigation
Bibliographic record
Abstract
The reaction of the anthracene adduct (PEt 3 ) 2 Ni(η 2 -C 14 H 10 ) with 1,2,3,4-tetrafluorobenzene revealed NMR spectroscopic evidence for the immediate equilibrium production of the dinuclear adduct [(PEt 3 ) 2 Ni] 2 (μ-η 2:η 2 -C 6 F 4 H 2 ) and mononuclear adducts (PEt 3 ) 2 Ni(η 2 -C 6 F 4 H 2 ). Similarly, the reaction of (PEt 3 ) 2 Ni(η 2 -C 14 H 10 ) with 1,2,4,5- and 1,2,3,5-tetrafluorobenzene revealed NMR spectroscopic evidence for the equilibrium production of the dinuclear adducts and mononuclear adducts and also the C−H activation products (PEt 3 ) 2 NiH(C 6 F 4 H). The conversions to both the adducts and C−H activation products were too minimal to allow for isolation, and the low concentrations hampered complete NMR spectroscopic characterization. The reaction of the readily prepared (PEt 3 ) 2 NiMe 2 with isobutene allowed for the in situ generation of (PEt 3 ) 2 Ni(η 2 -H 2 C═CMe 2 ) as a more reactive Ni(PEt 3 ) 2 synthon. The reaction of (PEt 3 ) 2 Ni(η 2 -H 2 C═CMe 2 ) with tetrafluorobenzenes also generates small equilibrium concentrations of adducts and C−H activation products, but the equilibrium can be driven by the removal of isobutene. The dinuclear adducts [(PEt 3 ) 2 Ni] 2 (μ-η 2:η 2 -1,2,3,4-C 6 F 4 H 2 ) and [(PEt 3 ) 2 Ni] 2 (μ-η 2:η 2 -1,2,4,5-C 6 F 4 H 2 ) were isolated and fully characterized by X-ray crystallography. The isolation of the dinuclear adduct of 1,2,3,5-tetrafluorobenzene was hampered by its rapid C−F activation and the generation of the less soluble aryne adduct [(PEt 3 ) 2 Ni] 2 (μ-η 2:η 2 -3,4,6-C 6 F 3 H), which was fully characterized. The spectroscopic characterization of all the tetrafluorobenzene mononuclear and dinuclear adducts as well as C−H activation products was accomplished by variable-temperature NMR spectroscopy and aided by DFT calculations on the proposed intermediates. The observation of equilibrium concentrations of the intermediates in solution allowed for the determination of the thermodynamic parameters for their interconversion.
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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 | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.003 | 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".