Diamines as interparticle linkers for silica–titania supported PdCu bimetallic nanoparticles in Chan–Lam and Suzuki cross-coupling reactions

Abstract

A series of highly efficient amine functionalized SiO₂–TiO₂ supported bimetallic PdCu catalysts with varied metal composition have been synthesized. Ethane-1,2-diamine, butane-1,4-diamine and hexane-1,6-diamine were employed as interparticle linkers for amine functionalization of a SiO₂–TiO₂ support material so as to study the effect of pendant chain length on stabilization and immobilization of bimetallic nanoparticles. The shortest carbon chain length on the support provided the best results, which may be due to the trapping of metal nanoparticles more efficiently by the basic nitrogen sites. The catalytic activities of these materials were evaluated for C–N and C–C coupling reactions. The most active catalyst, Pd₁Cu₁@12DA-STS, was characterized by various techniques including SEM, HR-TEM, ICP-AES, XRD, FTIR, EDX, CHN analysis and TGA studies. Moreover, the synthesized catalyst was found to be recyclable for up to five runs without significant loss of activity.