Electronic and Steric Parameters of 76 N-Heterocyclic Carbenes in Ni(CO)<sub>3</sub>(NHC)
Why this work is in the frame
A frame that forgets how it found something cannot be audited. These are the routes that admitted this work.
Bibliographic record
Abstract
We report electron-donor and steric properties of a diverse group of representative N-heterocyclic carbene (NHC) ligands quantified with the help of DFT calculations. This study afforded the conventional TEP data (Tolman electronic parameter = νCO (A1) of Ni(CO)3(NHC)), which allowed ranking 76 NHC ligands in order of increasing donor power. The TEP data reveal several general trends concerning the influence of NHC ring size, substitution, and annulation. The calculations also provided reaction enthalpies for CO elimination from the Ni(CO)3(NHC) complexes and formation of the 16-electron Ni(CO)2(NHC) species. This reaction is largely under steric control, which allowed defining a new steric descriptor for NHC ligands, r (“repulsiveness”) = 10 × (7.568 − 0.003172TEP − 0.0446ΔH), ranging from 0.0 for the smallest (ImNH2) to 8.0 for the most repulsive carbene (ImNAd2) of this work. Ni(CO)3L and Os(H2)Cl2(CO)L2 complexes eliminate CO and H2, respectively, more readily with L = NHC vs PR3 ligands. Apparently, even relatively small NHC ligands are very sterically demanding, and this property of N-heterocyclic carbenes may play a major role in coordination chemistry and catalysis.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 |
| 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 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 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