Phosphorus Chemical Shift Tensors for Tetramethyldiphosphine Disulfide: A <sup>31</sup>P Single-Crystal NMR, Dipolar-Chemical Shift NMR, and Ab Initio Molecular Orbital Study
Bibliographic record
Abstract
Phosphorus chemical shift and spin−spin coupling tensors have been characterized for tetramethyldiphosphine disulfide (TMPS) by analysis of 31 P CP NMR spectra obtained at 4.7 T for a single crystal. In addition, 31 P CP NMR spectra of stationary powder and magic angle spinning (MAS) samples have been acquired at two applied magnetic fields (4.7 and 9.4 T) and analyzed independently using the dipolar-chemical shift method. A 2D spin-echo NMR spectrum was also obtained to independently determine the effective 31 P− 31 P dipolar coupling constant. The crystal structure of TMPS (space group C 2 /m ) consists of six molecules per unit cell. For two of the six molecules, the two phosphorus nuclei are related by an inversion center (site 1), while the remaining four molecules possess mirror planes containing the S−P−P−S bonds (site 2). The differences between the two sites are very subtle, as revealed by a redetermination of the X-ray crystal structure. The phosphorus chemical shift tensors obtained from both single-crystal and dipolar-chemical shift NMR methods are in excellent agreement. For site 1, δ 11 = 91 ppm, δ 22 = 75 ppm, and δ 33 = −63 ppm with an error of ±2 ppm for each component. The principal components of the phosphorus chemical shift tensor at site 2 are very similar; δ 11 = 92 ppm, δ 22 = 74 ppm, and δ 33 = -59 ppm, again with errors of ±2 ppm. The phosphorus chemical shift tensors for both sites are oriented such that the direction of highest shielding is closest to the P−S bond while the direction of least shielding is perpendicular to the plane containing the S−P−P−S bonds. Ab initio (RHF and DFT) calculations of the phosphorus chemical shift tensors for both sites are in good agreement with experiment.
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 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".