Carbon−Hydrogen Bond Oxidative Addition of Partially Fluorinated Aromatics to a Ni(P<sup><i>i</i></sup>Pr<sub>3</sub>)<sub>2</sub>Synthon: The Influence of Steric Bulk on the Thermodynamics and Kinetics of C−H Bond Activation
Bibliographic record
Abstract
The reaction of (P i Pr 3 ) 2 NiCl 2 with the anthracene adduct (THF) 3 Mg(η 2 -C 14 H 10 ) in THF provides the anthracene adduct (P i Pr 3 ) 2 Ni(η 2 -C 14 H 10 ). In aromatic solvents (benzene, toluene, mesitylene) a thermal equilibrium exists between the bis(phosphine)nickel(0) anthracene adduct, (P i Pr 3 ) 2 Ni(η 2 -C 14 H 10 ), and the monophosphine solvent adduct, (P i Pr 3 )Ni(η 6 -solvent). The reaction of (P i Pr 3 ) 2 Ni(η 2 -C 14 H 10 ) with 1,2,4,5-C 6 F 4 H 2 affords the C−H activation product trans -(P i Pr 3 ) 2 NiH(2,3,5,6-C 6 F 4 H). The thermodynamic C−F activation product is not obtained even after hours of heating at 100 °C. Similar reactions with 1,2,3,5-C 6 F 4 H 2 and pentafluorobenzene produce the desired C−H activation products, trans -(P i Pr 3 ) 2 NiH(2,3,4,6-C 6 F 4 H) and trans -(P i Pr 3 ) 2 NiH(C 6 F 5 ), respectively, in >95% yield. The reaction with 1,2,3,4-tetrafluorobenzene did not produce an observable C−H activation product. Unlike previously reported analogous C−H activation products with Ni(PEt 3 ) 2 synthons, the bulkier Ni(P i Pr 3 ) 2 moiety did not provide observable mononuclear or dinuclear η 2 -fluoroarene adducts. Solutions of Ni(COD) 2 with 2 equiv of triisopropylphosphine and 1,2,4,5-C 6 F 4 H 2 reacted to give the 1,5-cyclooctadiene insertion and rearrangement product, (η 3 -C 8 H 13 )Ni(P i Pr 3 )(2,3,5,6-C 6 F 4 H). The same reaction with 1,2,3,5- and 1,2,3,4-C 6 F 4 H 2 afforded analogous compounds, which demonstrates that C−H bond activation is kinetically accessible at room temperature with 1,2,3,4-tetrafluorobenzene despite the presence of a single ortho -fluorine substituent adjacent to the site of activation. The room-temperature reactions of the C−H activation products (P i Pr 3 ) 2 NiH(Ar F ) (Ar F = 2,3,5,6-C 6 F 4 H; C 6 F 5 ) with 3-hexyne provided a mixture of the alkyne adduct (P i Pr 3 ) 2 Ni(η 2 -EtC≡CEt), with the liberation of Ar F H, and the insertion product (P i Pr 3 ) 2 Ni(CEt═CHEt)(Ar F ), even in the presence of excess fluorinated aromatic Ar F H. The reaction of (P i Pr 3 ) 2 Ni(η 2 -EtC≡CEt) with 1,2,4,5-C 6 F 4 H 2 resulted in no reaction at room temperature, but heating at 50 °C provided the insertion product (P i Pr 3 ) 2 Ni(CEt═CHEt)(Ar F ) as the initial product, followed by the product of reductive elimination, 1,2,4,5-C 6 F 4 H-CEt═CHEt. In contrast, the reaction of (PEt 3 ) 2 Ni(η 2 -EtC≡CEt) with 1,2,4,5-C 6 F 4 H 2 at 80 °C slowly produced (PEt 3 ) 2 Ni(CEt═CHEt)(2,3,5,6-C 6 F 4 H), but very little 1,2,4,5-C 6 F 4 H-CEt═CHEt.
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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 | 0.001 |
| 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 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 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".