摘要
以杂氮钼三环化合物H[MoO_2(OCH_2CH_2)_3N](A)或H{MoO_2[CH(CH_3)CH_2]_3N}(B)和咪唑为混合催化剂体系,研究了相转移条件下,环己烯与30％过氧化氢的环氧化反应。咪唑对提高反应活性起了关键的作用,在咪唑与钼化合物的摩尔比为2:1时,活性最好。IR研究表明反应过程中生成的红色物质是具有催化烯烃环氧化活性的钼过氧化物。还采用UV谱研究了咪唑与催化剂母体之间的作用,咪唑催化钼(Ⅵ)与H_2O_2反应生成活性钼(Ⅵ)过氧化物中间体,并参与对中心金属的配位,实验测得咪唑对钼的最大配位数是3。
In the presence of phase transfer catalysts, tetrapentylammonium bromide or cety] pyridinium bromide, 1,1-dioxomolybdatranic acids H[MoO2 -(OCH2CH2)3N] (A) or H[MoO2(CH(CH3)CH2)3N](B) and imidazole were first used as the catalyst in the epoxidation of cyclohexene with 30% aqueous hydrogen peroxide. The molar ratio of imidazole to molybdenum (Ⅵ) affected the reaction greatly, the reaction gave the highest yield of epoxide when the ratio was 2:1. A red intermediate was formed in the epoxidation reaction, and its IR spectrum showed that it was molybdenum (Ⅵ) peroxy complex, which was the active species in the epoxidation. The UV studies showed that the function of imidazole was to catalyze the formation of molybdenum (Ⅵ) peroxy complex and to coordinate with the central metal. The maximum coordination number of imidazole was 3.
