(±)-1,1′-Ethylenebis(4,5,6,7-tetrahydro-1-indenyl)zirconium Dichloride

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.