β-Hydrogen Elimination and Reductive Elimination from a κ<sup>3</sup>-PPC Nickel Complex
Bibliographic record
Abstract
The incorporation of a PPC donor ligand set onto nickel is described. While C–H activation routes using Ni(II) precursors and benzyl- and phenethyl-substituted diphosphines But2PCH2CH2P(But)R failed, success was achieved via oxidative addition of the 2-bromo-benzyl-ligand precursor But2PCH2CH2P(But)(CH2-o-C6H4Br) with Ni(COD)2 to generate [κ3-BnPPC]NiBr. Subsequent reaction with KBEt3H resulted in decomposition unless PPh3 was present, which allowed isolation of the tricoordinate Ni(0) complex [κ2-BnPP]Ni(PPh3). Reaction of [κ3-BnPPC]NiBr with EtMgCl also resulted in the formation of the Ni(0) ethylene complex, [κ2-BnPP]Ni(η2-C2H4), via β-elimination followed by reductive elimination. Deuterium-labeling studies are consistent with a reversible β-elimination process prior to reductive elimination, which scrambles the deuterium isotopes. Reaction of [κ3-BnPPC]NiBr with CH3Li results in the formation of the Ni(II) methyl complex, [κ3-BnPPC]Ni(CH3). Heating this species in the presence of PPh3 results in the formation of the Ni(0) derivative, [κ2-Bn-o-MePP]Ni(PPh3), in which reductive elimination of the methyl and aryl units has occurred. Reaction of [κ3-BnPPC]NiBr with heteroatom-containing species such as sodium isopropoxide, sodium 2-propanethiolate, and lithium methylphenylamide resulted in different outcomes depending on the heteroatom; with isopropoxide, the products isolated were geometric isomers of Ni(0) η2-acetone adducts, which presumably arise via a β-elimination–reductive elimination sequence; the analogous sulfur reagent generated isolable Ni(II) isopropyl thiolate species that was resistant to β-elimination upon thermolysis; with methylphenylamide, the Ni(II) amido complex could be isolated and structurally characterized; subsequent heating to 80 °C resulted in β-elimination followed by reductive elimination to generate a Ni(0) phenylimine complex. While the κ3-PPC donor set generates stable Ni(II) derivatives, further functionalization at nickel with hydride, alkyl, and heteroatom-containing moieties can lead to Ni(0) products via a combination of β-elimination and/or reductive elimination.
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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) | 0.006 | 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".