Organometallic Catalysts Immobilization And Catalytic Reactions In Aqueous Media Research

Mesoporos nanoparticles and Magnetic nanoparticles as two typiclal nano particles have been widely used in the field of immobilize catalysts onto supports. The superiority of mesoporos nanoparticles are large surface, uniform and changeable mesoporous tunes. The high surface and plenty of silanol groups make is easy to modification and dispersion. Due to their intrinsically supermangnetic property, Magnetic nanoparticles supported catalysts can be removed by applying an appropriate magnetic field near it, thus make recovery and recycle of catalyst much easier than those via filtration or centrifugation.In this paper, mesoporos nanoparticles and magnetic nanoparticles are used as supports, immobilize homogeneous catalysts on them and synthesize two kind of new catalysts, then used them in different reactions. The followings are the details:(1) PPh2-modified SBA-15 was prepared by a co-condensation method. The mesoporos nanoparticles supported bifunctional catalyst was prepared by postgrafting organometallic complex on PPh2-SBA-15. The mesostructured bifunctional catalyst showed high catalytic activity and selectivity under microwave irradiation in aqueous media. Furthermore, such a catalyst could be recovered and reused five times without loss of its catalytic activity and selectivity.(2) Superparmagnetic nanoparticles were prepared by a coprecipitation method. The silica-coating magnetic nanoparticle was formed by a base-catalyzed hydrolysis followed by polymerization reaction of tetraethoxysilane(TEOS) in reverse microemulsion. Then the magnetic nanoparticles-supported chiral rhodium and Iridium catalysts were obtained via immobilizing chiralη-Cp*-Rh-DPEN andη5-Cp*-Ir-DEPN onto magnetic nanoparticles. Both catalyst exhibit highly catalytic activities (up to 99%) and high enantioselectivities (up to 97%ee) in the asymmetric transfer hedrongenation of aromatic ketones. In particular, both hetogeneous catalysts can be recovered easily by using a magnet. Neither filtration nor extraction is necessary. The recycling catalysts (reuse 10 times for 5 and 6) still showed high catalytic efficiency without affecting obviously their enantioselectivities, showing good potential in industry application.