无配体Pd/LDH-F催化剂在Heck和Suzuki反应中的应用

 以氟离子插层的水滑石LDH-F为载体,用逐滴浸渍法制备了新型Pd/LDH-F催化剂,并用其催化溴代芳烃的Heck和Suzuki偶联反应. 用X射线衍射表征了催化剂的晶相,以等离子体发射光谱测定了溶剂中钯的流失量. 结果表明,对于Heck反应,在无配体存在和低钯用量(Pd/溴代芳烃摩尔比为0.001)的情况下, Pd/LDH-F的催化性能优于其它载体负载的Pd催化剂,显示出很高的催化活性和选择性. 在140 ℃和12 h的条件下, Pd/LDH-F催化溴苯与苯乙烯Heck反应产物的收率可达86％, 反应后催化剂经过分离,可循环使用四次其催化活性基本不变. 在DMF/水摩尔比为0.5的混合溶剂中,在室温和3 h 的条件下, Pd/LDH-F (Pd/溴代芳烃摩尔比为0.005)催化溴苯与苯基硼酸盐的Suzuki反应中,目标产物收率为99%.

Application of Ligand-Free Pd/LDH-F Catalyst in Heck and Suzuki Coupling Reactions

The palladium catalyst supported on fluoride pillared layered double hydroxide(LDH-F) was prepared by the incipient wetness method,and it was used to catalyze the Heck and Suzuki coupling reactions of aryl bromides.The structure of the Pd/LDH-F catalyst and the leaching of Pd in the solution were characterized by(X-ray) diffraction and inductively coupled plasma.With a small palladium dosage(Pd/aryl bromide molar ratio of 0.001) and no ligand,Pd/LDH-F exhibits higher catalytic activity and selectivity than the catalysts supported on other carriers for the Heck reaction of aryl bromides with styrene.The Pd/LDH-F catalyst can be easily separated from the reaction mixture and reused four times without loss in activity.Under the conditions of Pd/aryl bromide molar ratio of 0.005,room temperature and 3 h,the Pd/LDH-F catalyst can catalyze the Suzuki reaction of bromobenzene with a product yield of 99%.