Tetraphenylphosphonium Salts for Small Molecule Capture
Bibliographic record
Abstract
Tetraphenylphosphonium salts are useful tools for capturing (and crystallizing) small molecules. The packing of the cations in such salts leads to channels or cavities suitable for trapping of the small molecule by the anion. For example, we have prepared the complex salts [PPh4][SO2X] (X = Cl, Br, I) through the exposure of solutions of [PPh4]X to an atmosphere of SO2. Churakov et al. have reported the preparation of [PPh4]X·nH2O2 (X = Cl, Br; n = 0.98–1.90) after trapping hydrogen peroxide using the precursor halide salts (1). Envisioning a similar result, a concentrated solution of [PPh4]CN·xH2O was exposed to an atmosphere of CO2. Colourless crystals were isolated and characterised as [PPh4][NCCO2] using crystallographic and spectroscopic techniques. The packing of the ions in the product, in the tetragonal space group I-4, is similar to that observed in many other simple [PPh4]X salts, where X = Br, I, SCN, OCN, N(CN)2, etc. Solution of the crystal structure was complicated by the high symmetry and disorder in the anion, with only three unique atoms being necessary for its characterization. Thus the utility of our chosen cation can also become a hindrance. Crystals can usually be grown and data obtained but structure solution is not a certainty. For example, the structures of [PPh4]CN·xH2O have not been reported, likely because of the rapid spinning of the anions in the cation framework, even though they are hydrogen bonded to the water which is clearly visible. Similarly, we have data collected for the products from a number of related reactions, [PPh4][CN]·xH2O + PhC(O)F, [PPh4]F + SO2, [PPh4]X (X = Cl, Br, I, CN, N3) + CS2, and can clearly identify the cation in the unit cell. However, elucidation of the structures of the anions has not been possible. It is hoped that this presentation will engender discussion of possible solutions to the observed disorder problems.
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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 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.006 | 0.004 |
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".