Multinuclear Solid-State NMR Studies of Polymer-Supported Scandium Triflate Catalysts
Bibliographic record
Abstract
Scandium(III) trifluoromethanesulfonate [Sc(OTf) 3 ] is extensively used in organic synthesis to catalyze a wide variety of carbon–carbon bond-forming reactions in aqueous media. It has previously been demonstrated that it is possible to immobilize Sc(OTf) 3 in polystyrene (PS) to form the heterogeneous catalysts, microencapsulated (ME) Sc(OTf) 3 . The ME catalysts are recoverable, reusable, often reduce metal leaching, and have activity similar to that of their homogeneous counterparts. Aside from preliminary scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) imaging studies and solution 45 Sc NMR studies, there is little information available about the molecular and bulk structure of the ME catalyst. In this regard, we have conducted a 45 Sc solid-state NMR investigation of the Sc environments in the crystalline and ME forms of anhydrous Sc(OTf) 3 and hydrated Sc(OTf) 3 ·8H 2 O. Additional solid-state 1 H, 19 F, and 13 C NMR and powder X-ray diffraction experiments provide information that is complementary to that obtained from the 45 Sc NMR spectra, allowing for structural models of ME complexes to be proposed. The principal findings are that Sc(OTf) 3 is hydrated upon microencapsulation to form Sc(OTf) 3 ·8H 2 O. 1 H– 45 Sc TRAPDOR and 1 H– 19 F CP SSNMR experiments and powder X-ray diffraction experiments suggest that Sc is dispersed throughout the polymer within nanocrystalline domains of Sc(OTf) 3 ·8H 2 O. The approach outlined here should be applicable for the characterization of many other polymer-supported metal-based catalysts.
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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".