Heteroatom-Bridged Carba[2]ferrocenophanes with a Surprising Chemical Shift Pattern of Cp Protons
Bibliographic record
Abstract
[2]Ferrocenophanes bridged by a carbon and a heteroatom were targeted in the hope that such an asymmetric bridge gives rise to monomers suitable for ring-opening polymerization. Three strained sandwich compounds with bridging C–Si ( 13 SiMe2 ), C–P ( 13 PPh ), or C–B ( 13 BMes ) moieties were prepared using a lithium–bromine exchange followed by a common salt-metathesis reaction. Single-crystal X-ray structural analyses revealed an increase of the degree of Cp ring tilting, commonly expressed as the α angle, from 12.58(9) ( 13 SiMe2 ) to 16.63(2) ( 13 PPh ) to 19.66(11)° ( 13 BMes ). Despite being strained, all three species turned out to be resistant toward thermal ring-opening polymerization. The characterization of the three [2]ferrocenophanes by one- and two-dimensional 1 H NMR spectroscopy disclosed that Cp protons in α position to the bridging elements are deshielded relative to Cp protons in the β position. Experimental assignments were supported by DFT calculations of chemical shifts. The determined order of α and β Cp protons is opposite to that known for [1]ferrocenophanes. Using a set of known [ n ]ferrocenophanes ( n = 1, 2) with significant tilted Cp rings, DFT calculations revealed that both families exhibit a different order of Cp peaks in 1 H NMR spectra.
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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) | 0.002 | 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 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".