Montmorillonite Supported Pd/Cu Bimetallic Nanoparticle Catalyzed Sonogashira Coupling

To demonstrate the bimetallic effect of transition metal catalyzed C-C cross coupling, the montmorillonite (MMT) supported mixed palladium and copper nanoparticles were prepared and applied to catalytic Sonogashira couplings.A new method of preparing mixed metal nanoparticles was invented based on unique metal ion adsorption capacity of montmorillonite and sequential reductive carbonylation via thermolysis of N,N-dimethylformide, and Pd/Cu bimetallic nanoparticals was prepared in the ratio of 1∶1.A mixed solvent system, dimethoxyethane/water (V∶V＝1∶4) was identified as the best solvent of the catalytic coupling.MMT@Pd/Cu catalyzed efficiently the cross-coupling of aryl iodides and terminal aryland alkyl-ynes in presence of potassium carbonate and triphenyl phosphine.15 cross-coupling yne derivatives were isolated in excellent to moderate yields.Experimental kinetic study reveals that both swelling of montmorillonite promoted by water and Pd/Cu bimetallic synergistic effect play critical roles in high activity of the catalyst.Keywords transition metal catalysis; montmorillonite; C-C cross-coupling; bimetallic effect 发现催化活性物种是过渡金属催化碳碳键交叉偶 联反应研究的焦点问题之一 [1] .传统均相催化循环模型 认为, 配位不饱和单金属物种是该类反应的真正催化 剂 [1,2] .然而, 越来越多金属微粒催化反应的发现对该机 理提出了挑战 [1,3～5] .Beletskaya 等 [6] 认为金属微粒表面 的多金属协同效应极有可能是真正催化活性的起源, 而 很多报道的高效单金属催化剂实际上是催化活性金属 微粒的前驱体.实验证明, 催化反应体系内单金属配合 物、金属簇合物与纳米微粒之间存在复杂动态平衡 [6] .这种多物种之间平衡共存给探明真正催化活性物种带 来了困难.显然, 单金属催化反应难以证实多金属协同 作用.基于此, 我们选择异种双金属催化碳-碳键交叉 偶联反应为模型反应, 研究过渡金属催化交叉偶联反应 的多金属协同效应.经典 Sonogashira 偶联是构建有机分子碳碳叁键骨 架的有效策略,