1,4-Shifts in a Dinuclear Ni(I) Biarylyl Complex: A Mechanistic Study of C−H Bond Activation by Monovalent Nickel
Bibliographic record
Abstract
The known aryne complex (PEt3)2Ni(eta2-C6H2-4,5-F2) (1a) reacts with a catalytic amount of Br2Ni(PEt3)2 over 1% Na/Hg to afford the dinuclear Ni(I) biarylyl complex [(PEt3)2Ni]2(mu-eta1:eta1-3,4-F2C6H2-3',4'-F2C6H2) (2a), which results from a combination of C-C bond formation and C-H bond rearrangement. The dinuclear benzyne [(PEt3)2Ni]2(mu-eta2:eta2-C6H2-4,5-F2) (3) was obtained by the reaction of 1a with a stoichiometric amount of Br2Ni(PEt3)2 over excess 1% Na/Hg, and 3 was found to catalyze the conversion of 1a to 2a. The reaction of 1a with B(C6F5)3 produced the trinuclear complex (PEt3)3Ni3(mu3:eta1:eta1:eta2-4,5-F2C6H2)(mu3:eta1:eta1:eta2-4,5-F2C6H2-4',5'-F2C6H2) (6). The addition of PEt3 to 6 produced 1 equiv of 1a and 1 equiv of [(PEt3)2Ni]2(mu-eta1:eta1-4,5-F2C6H2-4',5'-F2C6H2) (7a). Both 6 and 7a were identified as intermediates in the conversion of 1a to 2a. The analogue [(PEt3)(PMe3)Ni]2(mu-eta1:eta1-4,5-F2C6H2-4',5'-F2C6H2) (7b) was prepared by the addition of PMe3 to 6 and was structurally characterized. NMR spectroscopic evidence identified the additional asymmetric biarylyl [(PEt3)2Ni]2(mu-eta1:eta1-4,5-F2C6H2-3',4'-F2C6H2) (8a) during the conversion of 1a to 2a. The initial observation of 2 equiv of 8a for every equivalent of 2a produced from solutions of 7a suggests that 8a and 2a are formed from a common intermediate. A crossover labeling experiment shows that the C-H bond rearrangement steps in the conversion of 1a to 2a occur with the intermolecular scrambling of hydrogen and deuterium labels. The evidence collected suggests that Ni(I) complexes are capable of activating aromatic C-H bonds.
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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 | 0.001 | 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".