New POCN-Type Pincer Complexes of Nickel(II) and Nickel(III)
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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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 | 0.001 |
| 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".