Bibliographic record
Abstract
[112243-79-5] C20H24Cl2Zr (MW 426.57) InChI = 1S/C20H24.2ClH.Zr/c1-3-7-19-15(5-1)9-11-17(19)13-14-18-12-10-16-6-2-4-8-20(16)18;;;/h9-12H,1-8,13-14H2;2*1H;/q;;;+2/p-2 InChIKey = AKXWJOYQORUUHS-UHFFFAOYSA-L (chiral metallocene complex for stereoselective alkene and silane polymerization;1 asymmetric hydrogenation catalyst for alkenes;2, 3 reagent for the asymmetric synthesis of allylic amines;4 asymmetric carbomagnesiation catalyst;5 precursor to chiral Lewis acid catalysts6) Physical Data: d 1.616 g cm−3 (calc). Solubility: insol hexanes, diethyl ether; sol CH2Cl2, CHCl3, THF; slightly sol toluene. Form Supplied in: crystalline white or pale yellow solid; not widely available. Analysis of Reagent Purity: 1H NMR and/or elemental analysis. Preparative Methods: by hydrogenation of the corresponding racemic ethylenebis(η5-indenyl)zirconium dichloride7a over PtO2 or 5% Pt/C at 1000 or 50–500 psi, respectively. The indenyl precursor is generally prepared from 1,2-bis(3-indenyl)ethane and ZrCl4 in THF solution via the dilithium7b or dipotassium salt3 of the former compound. In the former case, racemic material can be obtained in pure form (40–50% yields), whereas in the latter case the product (>70% crude) is contaminated with significant amounts of the meso isomer which can be removed by fractional crystallization from toluene. The racemate can be resolved on a gram scale by conversion to the (S)- or (R)-binaphtholate derivative.4, 8 Conversion, for example, of the (S,S)-binaphtholate derivative to the dimethylzirconocene derivative (MeLi, ether, or toluene) followed by treatment with either stoichiometric anhydrous dimethylamine hydrochloride (CH2Cl2) or anhydrous HCl (ether) provides optically pure material; [α]435 = +416°(c = 0.048 g 100 mL−1, CH2Cl2).8 Purification: the racemate is best crystallized from hot toluene. Optically pure material, which is much more soluble, is best crystallized from hexanes/toluene. Handling, Storage, and Precautions: the compound is air and moisture stable but is best stored for long periods of time (years) in a desiccator. No known toxic effects or safety hazards.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.012 | 0.011 |
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".