Anisotropic <sup>11</sup>B and <sup>13</sup>C NMR Interaction Tensors in Decamethylcyclopentadienyl Boron Complexes
Bibliographic record
Abstract
Solid-state double-resonance and triple-resonance 13 C, 11 B, and 1 H NMR experiments are used to investigate two main group metallocene complexes: the decamethylcyclopentadienylborinium cation, [Cp* 2 B] +, and bis(pentamethylcyclopentadienyl)methylborane, Cp* 2 BMe. The crystal structure for the latter complex is reported herein. A combination of magic-angle-spinning and static 11 B{ 1 H} NMR experiments are used to measure 11 B nuclear quadrupole coupling constants ( C Q ) and rare instances of anisotropic boron chemical shielding tensors. Boron-11 nuclear quadrupole coupling constants reflect the higher spherical symmetry of [Cp* 2 B] + compared to Cp* 2 BMe, with C Q ( 11 B) = 1.14 MHz in the former and C Q ( 11 B) = 4.52 MHz in the latter. Chemical shielding tensor spans are measured for [Cp* 2 B] + and Cp* 2 BMe as Ω = 73.0 and 146.0 ppm, respectively. Hartree−Fock and hybrid density functional theory (B3LYP) calculations of electric field gradient and chemical shielding tensors are in quantitative agreement with experiment, and are applied to examine the relationships between the anisotropic NMR interaction tensors and the structure and symmetry of these chemically analogous but structurally dissimilar boron complexes. Variable-temperature 11 B MAS NMR, 13 C CPMAS NMR, and 13 C/ 11 B/ 1 H CP TRAPDOR NMR experiments are applied to make a preliminary investigation of motion of the Cp* rings of [Cp* 2 B] + .
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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 | 0.000 | 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 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".