8-羟基喹啉双核钛配合物催化苯乙烯与双氧水的环氧化(英文)

Novel Di-μ-oxo Titano-8-Quinolinolato Complexes as Catalysts for the Epoxidation of Styrene with Aqueous Hydrogen Peroxide

合成了一类新型八羟基喹啉双核钛配合物,初步考察了这类配合物在催化烯烃与H2O2环氧化反应中的催化性能.结果表明配体的取代基对此类配合物的催化性能有很大的影响,由5,7-二卤代,特别是5-氯取代配体制备的配合物显示高的催化效率:它的催化转化率比普通喹啉配合物的催化转化率提高了44%,这可能与卤素取代基能加强配体与钛原子的配位作用有关.基于紫外技术,提出了此类钛配合物催化烯烃环氧化的机理:在酸性条件下,配合物中一个钛-氧-钛桥断裂,双氧水进攻后形成带氢键作用的过氧化物活性中间体,该中间体进一步生成了低活性的过氧化物.

This paper presents the synthesis of novel di-μ-oxo titano-8-quinolinolato complexes （HQ-Ti） and their catalytic performances in the epoxidation of styrene with aqueous hydrogen peroxide （ H2O2 ）. The obtained results indicate that the substituents of HQ ligand significantly influence the catalytic efficiency of the HQ-Ti complexes, in which the 5, 7-dihalogenated and especially 5-chloridated HQ-Ti catalysts achieve high epoxidation activities in water-acetone media with ammonium acetate and acetic acid as additives, being likely due to the halogen substituents strengthening the coordination of HQ toward Ti （IV） ions. Based on the UV-Vis characterization results, a mechanism for the HQ-Ti catalytic system is also proposed.