Chemical and Electrochemical Oxidation of <i>Tris</i>(3,5‐di‐<i>tert</i>‐butylphenyl)phosphine – High <i>Z′</i> Crystal Structures and Conformational Effects Associated with Bulky <i>meta</i> Substituents
Bibliographic record
Abstract
Synthesis and single‐crystal X‐ray diffraction structures of (3,5‐tBu2‐C6H3)3P, (3,5‐tBu2‐C6H3)3PO·H2O, (3,5‐tBu2‐C6H3)3PS and (3,5‐tBu2‐C6H3)3PSe are reported. The structure of (3,5‐tBu2‐C6H3)3P has Z′ = 4, with both M and P enantiomers of a helical conformation and a conformation with one flat ring in the same lattice. The pyramidality index, Σ{∠CPC}, is smaller for the helical compared to the flat conformers. All four have structures that are more pyramidal than the corresponding Ph3P(E) derivatives, which is attributed to stronger intramolecular dispersion forces. The oxide crystallizes with Z′ = 2 as a water‐bridged dimer that is the most separated such dimer amongst 26 known structures, providing evidence for a distal (or perimeter) steric effect. Cyclic voltammetry in CH3CN/[nBu4N][ClO4] indicated anodic peak potentials of +0.785 V for (3,5‐tBu2‐C6H3)3P, +0.745 for (3,5‐Me2‐C6H3)3P, +0.735 V for (4‐MeO‐3,5‐Me2‐C6H2)3P and +0.535 V for (4‐MeO‐C6H4)3P, all relative to Fc+/0. On this scale, Ph3P oxidizes at +1.04 V. The unexpectedly high oxidation potentials for the first three phosphines is attributed to a more pyramidal structure resulting in lowering of the HOMO energy compared to expectations from Hammett constants and 1J(P,Se) NMR coupling constants.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| 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 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".