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 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) | 0.000 | 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 | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".