Preparation, characterization and reactivity of mono- and dinuclear silica-supported titanium(IV) complexes.
Bibliographic record
Abstract
This thesis deals with the preparation, characterization and reactivity of silica-supported titanium(IV) complexes. The room temperature reactions of excess Ti(OiPr)4 with the hydroxyl groups of a nonporous silica yield dinuclear surface complexes regardless of the degree of partial dehydroxylation of the silica. The surface reactions were studied by in situ IR transmission spectroscopy, DRUV-vis, 13C CP/MAS NMR, GC/MS and elemental analysis. The spontaneous stoichiometric formation of both 2-propanol and propene during grafting indicates that interaction of Ti(OiPr)4 with the silica surface induces disproportionation of alkoxide ligands with concomitant formation of a Ti-O-Ti bridge. A synthetic route to mononuclear silica-supported Ti alkoxide complexes was developed by reaction of grafted amide complexes (≡SiO)nTi(NEt 2)4-n (n = 1 or 2) with alcohols. Subsequent reactions of the mononuclear surface alkoxide complexes with Ti(OiPr) 4 yield dinuclear species identical to those prepared by the direct reaction of Ti(OiPr)4 with silica. Both mono- and dinuclear supported alkoxide complexes undergo ligand exchange reactions with tert-butylhydroperoxide, but only the dinuclear alkylperoxo titanium surface complexes react with olefins to generate epoxides, which are formed quantitatively as the exclusive product at short reaction times. At longer contact times, the yield of epoxide decreases, without the appearance of other volatile oxidation products. It was discovered that the epoxide reacts with the catalyst and the product blocks the active site, inhibiting further epoxidation reaction with tert-butylhydroperoxide.
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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) | 0.000 | 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) | 0.000 | 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".