Steric Factors Affecting the Brønsted Acidity of Aluminosilsesquioxanes
Bibliographic record
Abstract
By reacting AlMe3 with two equivalents of (c-C5H9)7Si7O9(OH)2OSiR3, the corresponding Brønsted acidic aluminosilsesquioxanes [(c-C5H9)7Si7O11(OSiR3)]Al[(c-C5H9)7Si7O10(OH)OSiR3] [SiR3 = SiMe3 (1a), SiMePh2 (1b)] are obtained. These complexes readily react with triethylamine to yield the corresponding ammonium salts {[(c-C5H9)7Si7O11(OSiR3)]2Al}−{HNEt3}+ (2a,b). Hydrogen bonding between the acidic SiO(H)→Al proton and the pendant silyl ether function is effectively reduced by increasing the steric bulk of the silyl ether substituents, resulting in a higher acidity for 1b compared to that of 1a. With the silsesquioxane ligand (c-C5H9)8Si8O11(OH)2, which lacks pendant silyl ether functions, the acidic proton cannot satisfactorily be stabilized and this renders the putative Brønsted acid [(c-C5H9)8Si8O13]Al[(c-C5H9)8Si8O12(OH)] unstable. In the absence of proton acceptors, the disproportionation product [(c-C5H9)8Si8O13]3Al2 (3) is formed instead of the Brønsted acid. However, in the presence of triethylamine, the initially formed Brønsted acid readily transfers its proton to the amine, affording the ammonium salt {[(c-C5H9)8Si8O13]2Al}−{HNEt3}+ (4).
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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) | 0.002 | 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".