Impact of Backbone Substituents on POCOP-Ni Pincer Complexes: A Structural, Spectroscopic, and Electrochemical Study
Bibliographic record
Abstract
When treated at room temperature and in the presence of NEt 3 with {( i -PrCN)NiBr 2 } n, the pincer-type ligands R-POC H OP R ′ undergo direct C–H nickellation to give the pincer complexes (R-POCOP R ′ )NiBr in 45–92% yields (R-POCOP = κ P,κ C,κ P -{R n -2,6-(R′ 2 PO) 2 C 6 H 3– n }; R n = 4-OMe, 4-Me, 4-CO 2 Me, 3-OMe, 3-CO 2 Me, 3,5- t -Bu 2; R′ = i -Pr, t -Bu). These complexes have been characterized by multinuclear NMR and UV–vis spectroscopy as well as single-crystal X-ray diffraction studies to delineate the impact of R and R′ on Ni–ligand interactions. The solid-state structural data have revealed slightly shorter Ni–Br bonds in the complexes bearing a 4-CO 2 Me substituent, shorter Ni–P bonds in the complex bearing t -Bu substituents at the 3- and 5-positions, and longer Ni–P bonds in complexes featuring OP( t -Bu) 2 donor moieties. The UV–vis spectra indicate that a 4-CO 2 Me substituent causes a red-shift in the frequency of the MLCT bands (330–365 nm), whereas the ligand field transitions appearing in the 380–420 nm region are influenced primarily by the P -substituents. Cyclic voltammetry measurements have shown that the oxidation potentials of the title complexes are affected by P - and ring-substituents, oxidation being somewhat easier with t -Bu 2 PO (vs i -Pr 2 PO), OMe and Me (vs CO 2 Me), and t -Bu (vs Cl). Moreover, oxidation potentials are affected more by the aromatic substituents at the 4-position vs those at the 3- and 5-positions.
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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) | 0.001 | 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) | 0.038 | 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".