Preparation and Reactivities of PCP-Type Pincer Complexes of Nickel. Impact of Different Ligand Skeletons and Phosphine Substituents
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Bibliographic record
Abstract
Reaction of the diphosphine ligand i -Pr 2 P(CH 2 ) 5 P( i -Pr) 2 with NiBr 2 at 110 °C gives a mixture of the 16-membered bimetallacycle { i -Pr 2 P(CH 2 ) 5 P( i -Pr) 2 } 2 Ni 2 Br 4, 1, and the pincer-type complex {( i -Pr 2 PCH 2 CH 2 ) 2 CH}NiBr, 2; the latter can also be obtained by heating 1 in the presence of 4-(dimethylamino)pyridine or under vacuum. Complex 2 undergoes transmetalation with RMgCl or RLi to give {( i -Pr 2 PCH 2 CH 2 ) 2 CH}NiR (R = Me ( 4 ), C≡CMe ( 5 ), Ph ( 6 ), n -Bu ( 7 ), and C≡CPh ( 8 )); the phenylacetylide derivative 8 was also obtained from the reaction of PhC≡CH with 4, 5, or 7 . The Ni−Me derivative 4 reacts with PhX (X = I, Br, Cl) to give the product of C−C coupling reaction (Ph−Me) and the Ni−X analogues of 2, and tests have shown that 2 is a competent catalytic precursor for the coupling of PhCl and MeMgCl. The available evidence suggests that this catalytic process does not involve Ni 0 intermediates. Indeed, cyclic voltammetry measurements show that 2 can undergo two consecutive oxidations, and attempts to generate isolable high-valent species yielded the five-coordinate, 17-electron Ni III species {( i -Pr 2 PCH 2 CH 2 ) 2 CH}NiX 2, 9, from the reaction of 2 with FeX 3 (X = Cl, Br). Characterization of all new complexes, including X-ray diffraction studies on single crystals of complexes 1 − 6 and 9, is described.
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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) | 0.001 | 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 it