New POCN-Type Pincer Complexes of Nickel(II) and Nickel(III)
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Bibliographic record
Abstract
Unsymmetrical POC(H)N-type pincer ligands react with NiBr 2 (NCMe) x to give the complexes (POCN)Ni II Br (POCN= κ P,κ C,κ N -{2-( i -Pr 2 PO),6-(NR 2 CH 2 )-C 6 H 3 }; NR 2 = 3-morpholino ( 3a ), NMe 2 ( 3b ), and NEt 2 ( 3c )). The presence of an added base such as NEt 3 in these metalation reactions maximizes the yields of the target pincer complexes by suppressing the formation of side-products arising from protonation of the ligand by the in situ -generated HBr. The cyclic voltammograms of 3 exhibit a quasi-reversible, one-electron oxidation at ca. +1.0 V, in addition to an irreversible oxidation at higher potentials likely due to ligand oxidation. Reaction of the 16-electron, yellow complexes 3 with Br 2, N -bromosuccinimide, or CBr 4 gives black crystalline compounds identified as the 17-electron complexes (POCN)Ni III Br 2 ( 5 ). Complexes 3 and 5 adopt square-planar and distorted square-pyramidal geometries, respectively. The Ni−Br bond lengths in 5 are significantly longer for the Br atom occupying the axial position (2.43−2.46 vs 2.37 Å), consistent with the repulsive interactions expected between the bromide lone pair and the singly occupied d z 2 /d p z hybrid MO. In agreement with this picture, the g -values obtained from the EPR spectrum of 5a are g xx ≈ g yy ≈ 2.2, g zz ≈ 2.00, and strong Br hyperfine coupling is observed on the g zz component. Our preliminary studies indicate that the thermal stabilities of 5, both in the solid state (as probed by differential scanning calorimetry) and in solution (as probed by UV−vis spectroscopy), vary in the order 5a ≈ 5b > 5c; this order of stability is consistent with the relative steric demands of the N-moiety. Complexes 5a (or 3a ) and 5b (or 3b ) promote the Kharasch addition of CX 4 (X = Cl, Br) to styrene at 80 °C, giving PhC(X)CH 2 CX 3, the product of an anti-Markovnikov addition, in up to 50 catalytic turnovers.
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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 | 0.001 |
| 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) | 0.050 | 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