Immobilization of Heteroleptic Bis(oxazoline) Zinc Catalysts on SBA-15 for Asymmetric Hydrosilylation

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• 作者：Erwan Le Roux ; Aimery De Mallmann ; Nicolas Merle ; Mostafa Taoufik ; Reiner Anwander
• 刊名：Organometallics
• 出版年：2015
• 出版时间：October 26, 2015
• 年：2015
• 卷：34
• 期：20
• 页码：5146-5154
• 全文大小：502K
• ISSN：1520-6041

文摘

The C₂-symmetric bis(oxazoline)s (4S,4S)-R₁-BOX, with R₁ = tBu and Ph, react with ZnEt₂ straightforwardly to the four-coordinate complexes ((4S,4S)-R₁-BOX)ZnEt₂ in high yield. Their immobilization on highly dehydroxylated (700 掳C) mesoporous silica SBA-15 with enlarged pore diameters (d_p = 15.3 nm) led to the well-defined surface species [(鈮iO)Zn(Et)((4S,4S)-R₁-BOX)]. These ethyl zinc-terminated materials react readily with one equivalent of anhydrous methanol and acetic acid to give predominantly and selectively the corresponding surface ligand-exchanged species [(鈮iO)(Zn(R)((4S,4S)-R₁-BOX)] (R = OMe, OAc). All hybrid materials were characterized via N₂ physisorption, elemental analysis, DRIFT, ¹H/¹³C MAS NMR, and EXAFS spectroscopies. The SBA-15 supported heteroleptic bis(oxazoline) zinc ethyl, methoxide, and acetate surface species were scrutinized as catalysts for the asymmetric hydrosilylation of acetophenone.