Does Cr(CO)<sub>3</sub> Complexation Reduce the Aromaticity of Benzene?
Bibliographic record
Abstract
Ring currents in (C 6 H 6 )Cr(CO) 3, 1, ( cis -1,3-butadiene)Cr(CO) 4 ( 4 ), (C 6 H 6 ) 2 Cr ( 5 ), (C 4 H 4 )Fe(CO) 3 ( 6 ), and ( cis -1,3-butadiene)Fe(CO) 3 ( 8 ) have been assessed by σ−π disected nucleus independent chemical shift (NICS) calculations. Shielding contributions from the C−C(π) orbitals to the NICS values reveal that there is no quenching of ring current in the benzene ring of 1 or in dibenzene chromium 5 . The previously reported paratropic ring current for 1 is shown to be a consequence of latent aromaticity in 1,3-butadiene chromium tetracarbonyl 4 (one of the molecules used in the magnetic susceptibility equation). NICS values, a diatropic ring current, and a positive aromatic stabilization energy (ASE) all point to this aromaticity. NICS values for cyclobutadiene iron tricarbonyl, 6, show moderately sized diamagnetic shielding above the plane of the four-membered ring. In addition, 6 has a negative magnetic susceptibility exaltation (MSE) (diatropic ring current), quite opposite from the large paratropic current calculated for cyclobutadiene ( D 2 h ) itself. Evaluated using “strain corrected” isodesmic reactions, 6 has a large ASE in contrast to a large destabilization calculated for cyclobutadiene with the same equation. The 1,3-butadiene complex 8 also shows features of three-dimensional aromaticity, NICS(1) −8.7, NICS(1) π −2.8, and a moderate ASE stabilization energy (7.9 kcal/mol, eq 7), but this complex has a negligible MSE of −1.0 ppm cgs. We predict the ring current order to be the following: benzene ∼ 1 ∼ 5 > 6 > 4 > 8 .
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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 | 0.000 | 0.000 |
| 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".