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 aryl- and 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.