POCOP-Type Pincer Complexes of Nickel: Synthesis, Characterization, and Ligand Exchange Reactivities of New Cationic Acetonitrile Adducts
Bibliographic record
Abstract
This report describes the synthesis, characterization, and ligand exchange studies of a family of cationic acetonitrile adducts of nickel featuring resorcinol-based, pincer-type POCOP ligands. The compounds [(R-POCOP R ′ )Ni(NCMe)][OSO 2 CF 3 ] (R-POCOP R ′ = 2,6-(R′ 2 PO) 2 (R n C 6 H 3– n ); R′ = i- Pr: R = H ( 1 ), p- Me ( 2 ), p- OMe ( 3 ), p- CO 2 Me ( 4 ), p- Br ( 5 ), m,m-t -Bu 2 ( 6 ), m- OMe ( 7 ), m- CO 2 Me ( 8 ); R′ = t- Bu: R = H ( 9 ), p- CO 2 Me ( 10 )) were prepared in 80–93% yields by reacting the corresponding charge-neutral bromo derivatives with Ag(OSO 2 CF 3 ) in acetonitrile. The impact of the R- and R′-substituents on electronics and structures of 1 – 10 have been probed by NMR, UV–vis, and IR spectra, X-ray crystallography, and cyclic voltammetry measurements. The observed ν(C≡N) values were found to increase with the increasing electron-withdrawing nature of R, i.e., in the order 7 < 3 ∼ 2 ∼ 6 < 1 < 5 ∼ 8 < 4 and 9 < 10 . This trend is consistent with the anticipation that enhanced electrophilicity of the nickel center should result in an increase in net MeCN→Ni σ-donation. That this transfer of electron density from acetonitrile to the nickel center does not adequately counteract the impact of electron-withdrawing substituents was evident from the measured redox potentials: the MeO 2 C-substituted cations showed the highest oxidation potentials. Moreover, all cationic adducts showed greater oxidation potentials compared with their corresponding charge-neutral bromo precursors. Equilibrium studies conducted with selected [(R-POCOP R ′ )Ni(NCMe)][OSO 2 CF 3 ] and (R-POCOP R ′ )NiBr (R′ = i -Pr) have confirmed facile MeCN/Br exchange between these derivatives and show that the cationic adducts are stabilized with MeO-POCOP, whereas the charge-neutral bromo species are stabilized with MeO 2 C-POCOP. The potential implications of these findings for the catalytic reactivities of the title cationic complexes have been discussed.
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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 | 0.001 |
| 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) | 0.007 | 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".