A Measure for σ-Donor and π-Acceptor Properties of Diiminepyridine-Type Ligands
Bibliographic record
Abstract
Relative metal−ligand binding strengths for the ZnCl 2 and low-spin Co I Me fragments and a variety of diiminepyridine (DIP)-like ligands have been calculated at the DFT level. The assumption of a linear energy relation Δ E stab (F,L) = α F σ L + β F π L for the relative binding energy of fragment F to ligand L was used to derive scales for ligand parameters σ L and π L representing the σ-donor and π-acceptor qualities of these ligands. The results show that DIP ligands in general are only fair σ-donors but exceptionally good π-acceptors, being eclipsed only by their bis(diazo)pyridine analogues and bis(carbene)pyridine variations. Bis(phosphinimine)pyridines are much poorer π-acceptors than DIP, but are comparable in σ-donor capacity. Introduction of substituents at the pyridine or N-aryl rings of DIP results in changes that are much smaller than the above-mentioned replacement of the ligand side arms. The analysis method also puts metal fragments on a scale for Lewis acidity (α F ) and π-basicity (β F ). For the series of fragments ScCl 2 −CuCl 2 (all high-spin), results indicate that Lewis acidity increases almost monotonously; π-basicity decreases from ScCl 2 to MnCl 2 (where it vanishes), is significant again for FeCl 2, but negligible for CoCl 2 −CuCl 2 .
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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) | 0.004 | 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".