Replacing Chloride by Alkoxide: Cp<sub>2</sub>Zr(H)OR, Searching for Alternatives to Schwartz's Reagent
Bibliographic record
Abstract
Attempts to synthesize zirconocene hydrido alkoxide species, Cp 2 Zr(H)OR, via several synthetic pathways consistently failed to yield the targeted complexes, which seem prone to undergo disproportionation into Cp 2 ZrH 2 and a bisalkoxide complex. Reaction of Cp 2 ZrH 2 with HOR, Me 3 SiOR, or Ph 2 CO yielded the corresponding bisalkoxide complexes Cp 2 Zr(OR) 2, of which Cp 2 Zr{OC(H)Ph 2 } 2 was characterized by an X-ray diffraction study. Insertion of vinyl ethers into Cp 2 ZrH 2 yielded Cp 2 Zr(OR) 2 and Cp 2 Zr(Et)OR. Attempted hydrogenation of Cp 2 Zr(Me)OR or reaction of Cp 2 Zr(BH 4 )OR with NEt 3 did not yield the targeted complexes. Cp 2 Zr(H)OC 6 H 5 and Cp 2 Zr(H)OC 6 F 5 could be obtained, however, as transient species by β-H elimination from Cp 2 Zr( t Bu)OR, ligand exchange between Cp 2 ZrH 2 and Cp 2 Zr(OC 6 F 5 ) 2, or protonation in the presence of olefin to yield the corresponding hydrozirconation products. In hydrozirconation reactions of styrene both species are highly regioselective. The alkoxide substituent failed to inhibit β-H elimination in hydrozirconations of trans -3-hexene or β-OR elimination in reactions with vinyl ethers. On the other hand, it imparted a vastly increased thermal stability to the tert -butyl complexes Cp 2 Zr( t Bu)OR, which were stable for up to several months in solution, before they isomerize to the respective isobutyl complexes. Cp 2 Zr( i Bu)OC 6 H 5 was characterized by X-ray crystallography.
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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) | 0.003 | 0.001 |
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".