Measurement of Olefin Bond Rotation Barriers in a Series of Vinylaniline Complexes of the Cyclopentadienyliron(II) Dicarbonyl Cation and Their Correlation to Metal−Olefin Bond Asymmetry
Bibliographic record
Abstract
1 H NMR techniques (selective inversion, total line shape analysis, and T 1 ρ measurement) have been used to measure the olefin bond rotation rates in a series of compounds of the general formula CpFe(CO) 2 [η 2 -CH 2 C(H)NH(p−C 6 H 4 X)], where X = OMe ( 4 ), H ( 6 ), CN ( 9 ), NO 2 ( 10 ), Cl ( 11 ), COOMe ( 12 ). Complexes 4, 6, 11, and 12 enabled the use of all three methods to yield data sets that spanned a wide temperature range and allowed for reliable determination of the thermodynamic activation parameters for olefin bond rotation. When these three methods were combined with a bootstrap statistical analysis of the Eyring plots, it was possible to resolve the small differences in the Δ H ⧧ values between three of the four complexes. A clear trend is established between increasing electron donation from the aniline ligand and the facilitation of olefin bond rotation. These results are placed in the context of previous work, providing additional experimental evidence that electronic control from the para position of the aniline influences the overlap of the nitrogen lone pair with the adjacent olefinic carbon. This overlap controls the asymmetry in the metal−olefin bond by displacing the Fp + moiety away from the nitrogen-bearing carbon, which is reflected in a drop in the Δ H ⧧ value for olefin bond rotation.
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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) | 0.000 | 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) | 0.000 | 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 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".