Solid-State <sup>91</sup>Zr NMR of Bis(cyclopentadienyl)dichlorozirconium(IV)
Bibliographic record
Abstract
The first solid-state 91 Zr NMR spectra of an organometallic zirconium complex, bis(cyclopentadienyl)dichlorozirconium(IV) (Cp 2 ZrCl 2 ), are presented. Overlapping static and magic-angle spinning (MAS) 91 Zr NMR spectra of Cp 2 ZrCl 2 and a zirconium oxide NMR rotor are presented to explore the possibility of conducting 91 Zr NMR experiments using standard ZrO 2 rotors. Quadrupolar Carr−Purcell Meiboom−Gill (QCPMG) 91 Zr NMR experiments on static and MAS samples, in combination with analytical and numerical spectral simulations, are used to extract 91 Zr quadrupolar coupling constants and asymmetry parameters. The first example of zirconium chemical shielding anisotropy is reported for Cp 2 ZrCl 2, with a span of Ω = 475(45) ppm and a skew of −0.55(5) (i.e., δ 11 = 306 ppm, δ 22 = −62 ppm, and δ 33 = −169 ppm). Comparison of conventional static and MAS 91 Zr Hahn echo NMR spectra with those acquired using the recently reported double frequency sweep/QCPMG and rotor-assisted population transfer/QCPMG pulse sequences demonstrate an order of magnitude gain in sensitivity for Cp 2 ZrCl 2 . Restricted Hartree−Fock and hybrid density functional theory calculations reveal that anisotropic zirconium chemical shielding tensors can be calculated with good accuracy using non-relativistic theory with large all-electron basis sets. The 91 Zr quadrupolar parameters for Cp 2 ZrCl 2 are C Q = 6.35(10) MHz and η Q = 0.3(1). Reasonable agreement is obtained between calculated 91 Zr electric field gradient tensors and experimental results.
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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 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 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 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".