Experimental Study of the Reaction of a Ni(PEt<sub>3</sub>)<sub>2</sub> Synthon with Polyfluorinated Pyridines: Concerted, Phosphine-Assisted, or Radical C–F Bond Activation Mechanisms?
Bibliographic record
Abstract
The mechanisms of the C–F activation reactions of 2,3,5,6-tetrafluoropyridine and pentafluoropyridine with the phenanthrene adduct (PEt 3 ) 2 Ni(η 2 -C 14 H 10 ) and Ni(PEt 3 ) 4 as sources of (PEt 3 ) 2 Ni were investigated. The activation of 2,3,5,6-tetrafluoropyridine proceeds via the mononuclear adduct (PEt 3 ) 2 Ni(η 2 -2,3,5,6-C 5 F 4 HN) ( 3 ) in equilibrium with the C–H activation product, trans -(PEt 3 ) 2 NiH(2,3,5,6-C 5 F 4 N) ( 2 ). The C–F activation reaction occurs by concerted oxidative addition, as judged by the observation of cis -(PEt 3 ) 2 NiF(3,5,6-C 5 F 3 HN) ( 4 ), as an intermediate to trans -(PEt 3 ) 2 NiF(3,5,6-C 5 F 3 HN) ( 1 ). The dinuclear adduct [(PEt 3 ) 2 Ni] 2 (μ - η 2: η 2 -2,3,5,6-C 5 F 4 HN) ( 5 ) was not observed. Pentafluoropyridine reacted with the phenanthrene adduct (PEt 3 ) 2 Ni(η 2 -C 14 H 10 ) to provide the mononuclear adduct (PEt 3 ) 2 Ni(η 2 -C 5 F 5 N) ( 6 ) and the dinuclear adduct [(PEt 3 ) 2 Ni] 2 (μ - η 2: η 2 -C 5 F 5 N) ( 11 ). A (PEt 3 ) 2 Ni adduct of the C–F activation product, (PEt 3 ) 2 Ni[η 2 -3,4,5,6-C 5 F 4 N-2-NiF(PEt 3 ) 2 ] ( 10 ), and the double C–F activation product [ trans -(PEt 3 ) 2 NiF] 2 (3,4,5-C 5 F 3 N) ( 9 ) were also assigned by NMR spectroscopy. Complex 10 was a precursor to both trans -(PEt 3 ) 2 NiF(3,4,5,6-C 5 F 4 N) ( 7 ) and 9 . The rate of formation of trans -(PEt 3 ) 2 NiF(3,4,5,6-C 5 F 4 N) ( 7 ) is not first order with respect to the concentration of 6 . The EPR spectrum of (PEt 3 ) 2 Ni(η 2 -C 14 H 10 ) and pentafluoropyridine, in a toluene solution that was frozen in N 2 (l) during reaction at −40 °C, revealed signals consistent with the speculative formulation (PEt 3 ) 2 Ni(2-C 5 F 4 N). These results suggest that pathways other than concerted oxidative addition or phosphine-assisted pathways arising from 6 are required to account for the unusual selectivity of the C–F activation of pentafluoropyridine by the (PEt 3 ) 2 Ni fragment.
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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 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| 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) | 0.000 | 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".