Modification of Silica Surfaces by Metallasiloxanes Containing Mo and Ti: Evidence for Concurrent Metal and Ligand Chemisorption
Bibliographic record
Abstract
The molecular metallasiloxanes Mo(N t Bu) 2 (OSiMe 3 ) 2 1, and Ti(OSiMe 3 ) 4, 2, both react with the hydroxyl groups on partially dehydroxylated silica surfaces. The amount of chemisorbed metal corresponds, in both cases, to one-half the number of available surface hydroxyl groups. Unlike grafting reactions of metal alkoxides, the chemisorptions are not accompanied by release of protonated ligands. The siloxide ligands are transferred to the silica where they are bound via siloxane or “glass bonds”, as in ⋮SiOSiMe 3, 3 . By 13 C and 29 Si CP/MAS NMR, two distinct signals for trimethylsiloxide groups were observed. One is assigned to 3 by comparison to an authentic sample, while the second corresponds to trimethylsiloxide ligands coordinated to grafted metal complexes. The latter are susceptible to protonolysis, while 3 is not. The proposed grafting mechanism involves reaction of 1 or 2 with a single surface hydroxyl to form a chemisorbed metal complex and HOSiMe 3, followed by rapid condensation of the silanol with a second surface hydroxyl to generate 3 . Molecular metallasiloxanes are suggested as single-source precursors to metal catalysts supported on alkylsilane-capped surfaces.
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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".